HEAT AND MOISTURE RESISTANT SUBFLOOR AND OPTIONAL CEILING STRUCTURES MADE USING LIGHTWEIGHT COMPOSITE PANELS

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 63/764,340, filed Feb. 27, 2025, U.S. Provisional Application No. 63/753,600, filed Feb. 4, 2025, U.S. Provisional Application No. 63/692,563, filed Sep. 9, 2024, and U.S. Provisional Application No. 63/686,489, filed Aug. 23, 2024, which are incorporated by reference in their entirety.

BACKGROUND

Technical Field

This disclosure relates to methods and systems for making subfloor and optional ceiling structures for buildings using lightweight composite panels.

Related Technology

Floor and ceiling assemblies are critical in building construction, serving as structural components and barriers for fire, sound, and thermal transmission. Traditional subfloor assemblies typically use plywood, oriented strand board (“OSB”), or gypsum board as subfloor sheathing. The finished floor surface, such as hardwood, tile, vinyl, laminates, engineered wood planks, or carpet, are fastened or bonded to the subfloor sheathing. Subfloor sheathing is typically placed over and fastened to joists or beams, in the case of typical floors, to furring positioned over a concrete slab for some types of floors on grade, or over foam insulating sheets for other types of floors on grade.

A traditional flooring system typically consists of the following key elements: (1) structural subfloor; (2) underlayment; (3) finish flooring; (4) fasteners and adhesives; and (5) optional moisture barrier. The structural subfloor is usually made of plywood, OSB or gypsum-based sheathing, is installed directly to floor joists to provide a stable base, and acts as the primary load-bearing layer, distributing loads to the underlying structural framework. An underlayment is typically installed over the subfloor to create a smooth surface for the final flooring material and is commonly made of materials such as cement board, fiberboard, or foam-based products, offering soundproofing, moisture resistance, and support for finish layers. The finish flooring is the topmost visible layer, which can include hardwood, tile, vinyl, carpet, or laminate, selected based on aesthetic and functional requirements and may be applied directly on top of the sheathing. Fasteners and adhesives include nails, screws, or construction adhesives to secure the subfloor to the joists to ensure stability. The optional moisture barrier can be provided by a layer of waterproofing material, which may be added beneath or above the subfloor, especially in wet or moisture prone areas such as kitchens or bathrooms, to protect against water damage. When using tile as the final flooring material, underlayment can also serve an uncoupling layer between the bonded tile and sheathing to accommodate some building movement and reduce cracking.

Traditional subfloor sheathing, however, presents significant limitations. For example, plywood, OSB panels, and gypsum board can absorb water, leading to mold growth and structural degradation in high-humidity environments or areas prone to water intrusion. In addition, they typically offer minimal insulation, reducing energy efficiency, unless paired with insulation, which requires an extra step. Gypsum-based panels, although capable of providing some resistance to fire and heat, are cumbersome and increase labor requirements and the risk of worker injuries during installation. On the other hand, traditional wood sheathing materials, although strong and versatile, are also heavy and cumbersome and do not provide any fire resistance. In some cases, floor and subfloors may be required to provide fire resistance under ASTM E119 or UL rated assemblies.

Accordingly, there is a need for improved subfloors and methods and systems for constructing subfloors, including subfloors that can reduce time, weight, and labor costs, and provide improved resistance to heat and moisture compared to traditional subfloors.

SUMMARY

Disclosed are methods and systems for constructing subfloors of buildings that address and overcome problems associated with traditional subfloors. This is accomplished by using lightweight composite subfloor panels that replace or augment traditional plywood panels used to make subfloors. Also disclosed are methods and systems for constructing subfloors and optional ceilings of buildings having upper and lower floors using lightweight composite panels for both subfloor and ceiling structures. A floor finish can be applied over lightweight composite subfloor panels to yield a finished floor. Optionally, a ceiling finish can be applied over lightweight composite ceiling panels. By using lightweight composite panels, the subfloors and optional ceiling structures disclosed herein have greatly improved moisture, fire and heat resistance, as well as lower weight, inhibition of mold growth, and case of installation, compared to traditional subfloors made using plywood, OSB panels, and gypsum board.

In some embodiments, a method of constructing a subfloor of a building, comprises: (1) forming or providing a subfloor support structure that includes a subfloor framework comprising joists, beams, furring strips, and/or foam shects and optionally intermediate sheathing fastened to or applied over the subfloor framework; and (2) fastening a plurality of lightweight composite subfloor panels over the subfloor support structure to form a subfloor over which a floor finish can be applied, (3) the lightweight composite subfloor panels each comprising: (a) a foam core (e.g., polymer or inorganic foam) having a first surface, a second surface opposite the first surface, a first edge forming a perimeter of the first surface, a second edge forming a perimeter of the second surface, and side surfaces extending between the first and second edges; (b) a first protective layer (e.g., first fiber mesh reinforced cementitious layer, thermoset polymer, or other rigid material) formed over and covering at least a portion of the first surface of the foam core; and (c) a second protective layer (e.g., second fiber mesh reinforced cementitious layer, thermoset polymer, or other rigid material) formed over and covering at least a portion of the second surface of the foam core, (4) wherein the lightweight composite subfloor panels are positioned so that one protective layer faces toward and the other protective layer faces away from the subfloor support structure.

In some embodiments, a subfloor of a building, comprises: (1) a subfloor support structure that includes a subfloor framework comprising joists, beams, furring strips, and/or foam sheets and optionally an intermediate sheathing fastened to or applied over the subfloor framework; and (2) a plurality of lightweight composite subfloor panels fastened over the subfloor support structure to form a subfloor over which a floor finish can be applied, (3) the lightweight composite subfloor panels each comprising: (a) a foam core (e.g., polymer or inorganic foam) having a first surface, a second surface opposite the first surface, a first edge forming a perimeter of the first surface, a second edge forming a perimeter of the second surface, and side surfaces extending between the first and second edges; (b) a first protective layer (e.g., first fiber mesh reinforced cementitious layer, thermoset polymer, or other rigid material) formed over and covering at least a portion of the first surface of the foam core; and (c) a second protective layer (e.g., second fiber mesh reinforced cementitious layer, thermoset polymer, or other rigid material) formed over and covering at least a portion of the second surface of the foam core, (4) wherein the lightweight composite subfloor panels are positioned so that one protective layer faces toward and the other protective layer faces away from the subfloor support structure.

In some embodiments, the subfloor support structure includes intermediate sheathing, which may comprise sheathing selected from the group consisting of plywood, oriented strand board (OSB), gypsum board, a plurality of lightweight composite sheathing panels, and combinations thereof. In such cases, the lightweight composite subfloor panels forming the subfloor can be fastened to the intermediate sheathing to form a substrate or underlayment over which a floor finish can be applied.

In other embodiments, the subfloor support structure omits the intermediate sheathing. In such cases, the lightweight composite subfloor panels can be fastened to the subfloor framework to form the subfloor over which a floor finish can be applied.

In yet other embodiments, the subfloor support structure includes two layers of lightweight composite subfloor panels, a first layer of generally thicker panels attached to the subfloor framework as intermediate sheathing and a second layer of generally thinner panels placed over the first layer of generally thicker panels to function as a substrate or underlayment over which a floor finish can be applied.

In some embodiments, the subfloor forms part of a bottom floor of a building or is below grade and forms part of a basement floor of a building. In other embodiments, the subfloor separates an upper floor and a lower floor of a building, wherein the subfloor framework comprises joists or beams and the subfloor support structure forms the subfloor of the upper floor. In such cases, a plurality of lightweight composite ceiling panels can be positioned beneath and fastened to below (e.g., to an underside of) the subfloor framework to form a ceiling structure of the lower floor. In some embodiments, the lightweight composite ceiling panels used to form the ceiling structure may comprise modified lightweight composite panels that have a plaster finish, UV or chemical cured polymer finish, or paper layer on the exterior protective layer (e.g., fiber mesh reinforced cementitious layer) of the lightweight composite ceiling panels to which paint, wallpaper, tiles, or other ceiling finish can be applied.

Because the lightweight composite ceiling panels are rigid, dimensionally stable, and waterproof, they resist sagging and deformation under gravity loads or exposure to humidity. Unlike conventional gypsum panels, which typically require a minimum thickness of ⅝″ for ceiling applications to prevent sagging, the composite panels can achieve comparable or superior performance at reduced thicknesses. This allows for the use of thinner, lighter panels on ceilings while maintaining structural integrity and long-term flatness.

In some embodiments, the subfloor structure may further comprise insulation positioned within the subfloor framework, such as between joists, beams, or furring strips and below the subfloor and above the optional ceiling structure.

In some embodiments, a finished floor can include a floor finish applied over the subfloor, such as by being fastened or bonded to the lightweight composite subfloor panels of the subfloor.

In some embodiments, the lightweight composite subfloor panels are fastened to the subfloor support structure by at least one of screws, nails, other mechanical fasteners, or an adhesive. When used, the screws or other mechanical fasteners can include corresponding washers or enlarged heads also known as pan head screws or screws with integrated washers that are at least about 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 m, 65 cm, 70 cm, 75 mm, or 80 mm, in diameter to prevent damage to the exterior fiber mesh reinforced cementitious (or other protective) layer of the lightweight composite subfloor panels. In some embodiments, the washers may further include a plurality of penetrating prongs configured to penetrate at least partially through the lightweight composite subfloor panels, including through the exterior fiber mesh reinforced cementitious (or other protective) layer and at least partially through the foam core, such as where the penetrating prongs penetrate all the way through the lightweight composite subfloor panels and make abutment with the subfloor support structure. In some embodiments, the subfloor can include a seam coat applied over exposed fasteners and joints or seams between adjacent lightweight composite subfloor panels. Optional lightweight composite ceiling panels can be attached in a similar manner or using known fastening means.

Additional features and advantages will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the embodiments disclosed herein. It is to be understood that both the foregoing brief summary and the following detailed description are exemplary and not restrictive of the embodiments disclosed herein or as claimed

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects, features, characteristics, and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings and the appended claims, all of which form a part of this specification. In the Drawings, like reference numerals may be utilized to designate corresponding or similar parts in the various Figures, and the various elements depicted are not necessarily drawn to scale, wherein:

FIG. 1 illustrates an example floor finish, which includes natural wood or engineered wood or polymer floor boards, applied over a subfloor;

FIG. 2 illustrates example plywood sheathing used to make a subfloor, including a pair of adjacent plywood boards that join together by tongue and groove connection;

FIG. 3A is a cross-sectional view of an example floor and ceiling structure made using lightweight composite subfloor panels applied over a subfloor support structure and lightweight composite ceiling panels positioned below the subfloor support structure;

FIG. 3B is a closeup cross-section view of the example floor and ceiling structure of FIG. 3A;

FIG. 3C is an exploded view of the example floor and ceiling structure of FIGS. 3A and 3B;

FIG. 4 is a cross-sectional view of another example floor and ceiling structure made using lightweight composite subfloor panels applied over a subfloor support structure and lightweight composite ceiling panels positioned below the subfloor support structure;

FIG. 5A is a side perspective view that that illustrates examples of differently sized lightweight composite panels that can be used to make subfloors and optional ceilings;

FIG. 5B is a top perspective view that illustrates the differently sized lightweight composite panels of FIG. 5A;

FIG. 5C is an exploded diagram that schematically illustrates the layered structure of the lightweight composite panels of FIGS. 5A and 5B;

FIG. 6A is a perspective view that illustrates an example lightweight composite plaster panel, with the different layers being visible, that can be used to make an optional ceiling structure below a subfloor of the disclosure;

FIG. 6B illustrates a pair of lightweight composite plaster panels abutting each other, with beveled edges forming a channel or depression that can be filled with tape and drywall patch during installation of ceiling panels below a subfloor of the disclosure;

FIG. 6C is a photograph showing a pair of lightweight composite plaster panels abutting each other, with beveled edges covered and filled in with drywall patch;

FIG. 6D is a side cross-sectional view showing different layers of a lightweight composite plaster panel and bevels extending to the edges;

FIG. 6E is an exploded diagram that schematically illustrates the layered structure of the lightweight composite plaster panels of FIGS. 6B-6D;

FIG. 6F is a perspective view that schematically illustrates an embodiment of a lightweight composite plaster panel as in FIGS. 6B-6E with bevels extending to the four edges;

FIG. 7A is an exploded diagram that schematically illustrates the layered structure of another example lightweight composite plaster panel with beveled edges that can be used to make a ceiling structure beneath a subfloor of the disclosure;

FIG. 7B is a side cross-sectional view that schematically illustrates the layered structure of the example lightweight composite plaster panel of FIG. 7A;

FIG. 8 illustrates a lightweight composite panel with holes caused by screws with heads that penetrated through the fiber mesh reinforced cementitious layer and a screw with a washer that did not penetrate through the cementitious layer; and

FIGS. 9A-9D illustrate embodiments of specialized washers with multiple prongs designed to penetrate at least partially through and become embedded within lightweight composite panels used to make subfloors and optional ceilings of the disclosure.

DETAILED DESCRIPTION

I. Introduction

Disclosed are methods and systems for constructing subfloors of buildings that address and overcome problems associated with traditional subfloors. This is accomplished by using lightweight composite subfloor panels that replace or augment traditional wood panels used to make subfloors. By using lightweight composite subfloor panels, the subfloors disclosed herein have greatly improved moisture and heat resistance, as well as lower weight and case of installation, compared to traditional subfloors made using plywood, OSB, or gypsum board. A floor finish can be applied over the lightweight composite subfloor panels to form a finished floor.

Also disclosed are methods and systems for constructing subfloor and ceiling structures of a building having upper and lower floors using lightweight composite subfloor panels to form a subfloor of the upper floor over which a floor finish can be applied and lightweight composite ceiling panels to form a ceiling of the lower floor. In some embodiments, the lightweight composite ceiling panels can be fastened to the bottom of floor joists supporting the subfloor to form the ceiling structure to which a ceiling finish can be applied.

For purposes of this disclosure, the term “lightweight composite subfloor panels” can include the following uses: (1) lightweight composite panels used as a substrate or underlayment between intermediate subfloor sheathing, such as plywood or OSB panels, and a floor finish; (2) lightweight composite panels fastened directly to a subfloor framework (e.g., joists, beams, furring strips, and/or foam sheets) to form a subfloor over which a floor finish is applied; and (3) lightweight composite panels fastened to a subfloor framework as intermediate subfloor sheathing in place of conventional plywood or OSB subfloor panels and beneath a second layer of lightweight composite panels used as a substrate or underlayment for attachment of a floor finish.

One advantage of the methods and systems for constructing subfloors as disclosed herein is to yield a high-performance floor and optional ceiling assembly using lightweight composite panels, which can provide enhanced fire safety, moisture protection, thermal insulation, and case of installation. Because the panels are rigid, dimensionally stable, and waterproof, they maintain flatness and structural integrity under gravity loads or humidity exposure greatly reducing or eliminating sag when applied to ceilings. The case of installation leverages the various components of lightweight composite panels, including a fire- and moisture-resistant foam (e.g., polymer or inorganic) core sandwiched between fiber reinforced cementitious (or other protective) layers, offering a lightweight and durable alternative to traditional plywood, OSB, or gypsum-based sheathing. The subfloor systems disclosed herein can provide improved performance while reducing labor costs and addressing challenges of high-humidity environments.

In some embodiments, the methods and systems for constructing subfloors of buildings utilize lightweight composite subfloor panels as a replacement for traditional subfloor sheathing (i.e., plywood, OSB, or gypsum board). In such embodiments, lightweight composite subfloor panels can be fastened or bonded directly to the subfloor framework, such as floor joists, beams, furring strips, and/or foam sheets. A desired floor finish can be fastened or otherwise applied over the lightweight composite subfloor panels.

In other embodiments, the methods and systems for constructing subfloors of buildings utilize lightweight composite subfloor panels as the main underlayment over traditional subfloor sheathing (i.e., plywood, OSB, or gypsum board). In such embodiments, lightweight composite panels can be fastened to an intermediate underlayment comprising traditional sheathing fastened to the subfloor framework, such as floor joists, beams, furring strips, and/or foam sheets. A desired floor finish can be fastened or otherwise applied over the lightweight composite subfloor panels.

Lightweight composite subfloor panels include a strong yet lightweight polymer or inorganic foam core sandwiched between relatively thin protective layers (e.g., fiber reinforced cementitious layers, thermoset polymer layers (optionally fiber-reinforced), and magnesium oxide or other rigid layer). As a result, the lightweight composite subfloor panels are strong and can support relatively heavy loads, such as a floor finish and loads typically borne by floors, such as people, furniture, and appliances. The lightweight composite subfloor panels are lightweight yet waterproof, mold resistant, heat resistant, and fire resistant, and have high structural strength (i.e., high tensile and flexural strength and high toughness). The lightweight composite subfloor panels can be cut, drilled, and screwed, fastened and/or glued onto a subfloor support structure, including a subfloor framework comprising joists, beams, furring strips, and/or foam sheets, and optionally an intermediate underlayment comprising sheathing fastened to or applied over the subfloor framework. The interior-facing fiber mesh reinforced cementitious (or other protective) layer can provide a bonding surface that facilitates adhesion of lightweight composite subfloor panels to structural elements of the subfloor support structure. The optional lightweight composite ceiling panels can have similar construction and properties, and may include a plaster layer, UV or chemical cured polymer layer, or paper layer to which paint or other ceiling finish can be applied.

Lightweight composite panels are capable of providing protection against fire due to their ASTM E84 Class A fire rating. In the case where the foam core is a polymer foam, particularly when treated with a fireproofing material, the polymer foam core may melt but will not easily burn. In the case where the foam core is an inorganic foam, particularly a refractory foam material, the inorganic foam core may not be damaged in order for the lightweight composite panels to maintain their structural integrity even when exposed to fire or intense heat.

Additional information regarding lightweight composite subfloor and optional ceiling panels is set forth in a later section below, including disclosure relating to FIGS. 5A-7B. Additional information regarding fasteners that can be used to fasten lightweight composite subfloor and optional ceiling panels to a subfloor support structure is set forth in a later section below, including disclosure relating to FIGS. 8-9D.

Additional information and features relating to lightweight composite panels and their uses in making various building products are disclosed in U.S. Prov. App. No. 63/686,489, filed Aug. 23, 2024; U.S. Prov. App. No. 63/692,563, filed Sep. 9, 2024; U.S. Prov. App. No. 63/703,834, filed Oct. 4, 2024; U.S. Prov. App. No. 63/720,649, filed Nov. 14, 2024; U.S. Prov. App. No. 63/729,637, filed Dec. 9, 2024; U.S. Prov. App. No. 63/744,115, filed Jan. 10, 2025; U.S. Prov. App. No. 63/747,543, filed Jan. 1, 2025; U.S. Prov. App. No. 63/753,600, filed Feb. 4, 2025; U.S. Prov. App. No. 63/764,354, filed Feb. 27, 2025; U.S. Prov. App. No. 63/788,276, filed Apr. 14, 2025; U.S. Prov. App. No. 63/849,709, filed Jul. 23, 2025, U.S. Prov. App. No. 63/855,715, filed Aug. 1, 2025, U.S. Prov. App. No. 63/857,807, filed Aug. 5, 2025, and U.S. Prov. App. No. 63/862,235, filed Aug. 12, 2025. The foregoing applications are incorporated by reference in their entirety.

II. Methods and Systems for Constructing Subfloor and Optional Ceiling Structures

Reference is now made to FIGS. 1 and 2, which illustrate a typical floor finish and sheathing, and FIGS. 3A-4, which illustrate embodiments of subfloors and optional ceiling structures and components used to make subfloors and optional ceiling structures.

FIG. 1 illustrates an example of wood flooring 100, such as flooring made with hardwood, softwood, engineered wood or polymer planks. Other examples of floor finishes that can be applied over the subfloor structures disclosed herein include, but are not limited to, tiles, stone veneers, decorative concrete units, vinyl, carpet, and linoleum (not shown).

FIG. 2 illustrates an example of traditional subfloor sheathing 200 that can be fastened to or applied over joists, beams, furring strips, or foam boards forming a subfloor framework. The subfloor sheathing 200 in this example comprises a first plywood board 202a and a second plywood board 202b, which can be joined together by a tongue and groove system 204. Other examples of subfloor sheathing include OSB panels and gypsum boards (not shown).

FIGS. 3A-3C illustrate an embodiment of a subfloor and ceiling structure 300 made using intermediate sheathing that is covered by lightweight composite subfloor panels to form a subfloor that provides a smooth and uniform underlayment for attachment of a floor finish. The subfloor and ceiling structure 300 of this example can be used for installation thereon of a hardwood or engineered wood floor finish 302. The subfloor and ceiling structure 300 also includes lightweight composite ceiling panels that form a ceiling structure to which a desired ceiling finish can be applied. Thus, subfloor and ceiling structure 300 is positioned between and separates an upper floor and a lower floor of a building.

As more particularly shown and numbered in FIGS. 3B and 3C, the subfloor and ceiling structure 300 includes engineered I-beam joists 308 having upper flanges 310a and lower flanges 310b, which provide structural strength and structural elements of a subfloor framework to which intermediate sheathing 306 and lightweight composite subfloor panels 304 and lightweight composite ceiling panels 314 can be fastened. The subfloor and ceiling structure 300 may also include insulation 312 between the I-beam joists 308, which can provide thermal and sound insulation between the upper and lower floors.

The subfloor and ceiling structure 300 includes intermediate sheathing 306 fastened to the upper flanges 310a of the I-beam joists 308, which together form a subfloor support structure. The intermediate sheathing 306 may comprise traditional sheathing, such as plywood, oriented strand board (OSB), and/or gypsum board. Alternatively, the intermediate sheathing 306 may comprise an intermediate layer of lightweight composite sheathing panels, which can have the same or different construction as the lightweight composite subfloor panels 304.

The lightweight composite subfloor panels 304 are fastened to the intermediate sheathing 306 of the subfloor support structure to form a subfloor and underlayment to which the floor finish 302 can be fastened or applied. When used in this manner, the lightweight composite panel underlayment can also serve as an uncoupling layer between the subfloor panels and tile finishes, helping to accommodate some movement and reduce the risk of cracking. Because the lightweight composite subfloor panels 304 are waterproof and provide a water-resistance barrier, traditional underlayments (e.g., polymer or fiber sheets) used to cover conventional sheathing panels or concrete floors can be omitted.

The subfloor and ceiling structure 300 furthers include a ceiling structure above a lower floor comprising lightweight composite ceiling panels 314 fastened to the lower flanges 310b of the I-beam joists 308. The lightweight composite ceiling panels 314 can have the same or different construction as the lightweight composite subfloor panels 304. As discussed below, the lightweight composite ceiling panels 314 can include a plaster layer, UV or chemical cured polymer layer, or paper layer to which paint or other ceiling finish can be applied.

FIG. 4 illustrates an alternative embodiment of a subfloor and ceiling structure 400 that omits the intermediate sheathing layer. Rather, the subfloor and ceiling structure 400 includes a single subfloor layer and underlayment comprised of lightweight composite subfloor panels 404 fastened to upper surfaces of joists 406. A floor finish 402 (e.g., hardwood floor boards, engineered wood flooring, laminates, tiles, stone veneers, concrete units, vinyl flooring, linoleum, carpet, and the like) is fastened to or otherwise applied over the lightweight composite subfloor panels 404. Because the lightweight composite subfloor panels 304 are waterproof and provide a water-resistance barrier, traditional underlayments (e.g., polymer or fiber sheets) used to cover conventional sheathing panels or concrete floors can be omitted.

As illustrated, the subfloor and ceiling structure 400 may further include a ceiling structure comprising lightweight composite ceiling panels 408, which are fastened to lower surfaces of joists 406. The subfloor and ceiling structure 400 may also include insulation (not shown) to provide thermal and/or sound insulation between upper and lower floors of a building.

The lightweight composite panels used in the example subfloor and ceiling structure 300 of FIGS. 3A-3C and the example subfloor and ceiling structure 400 of FIG. 4 can have appropriate thicknesses based on their intended function.

In the example subfloor and ceiling structure 300 illustrated in FIGS. 3A-3C, the lightweight composite subfloor panels 304 fastened to the intermediate sheathing 306 can have a relatively thin cross-sectional thickness, such as a thickness of about 3/16 inch to about ½ inch, or about 7/32 inch to about ⅜ inch, or about ¼ inch. The lightweight composite subfloor panels 304 can be relatively thin in cross-sectional thickness between the intermediate sheathing 306 can provide the main load-bearing support structure between the I-beam joists 308 and the floor finish 302. The lightweight composite subfloor panels 304 are primarily used to provide a water- and fire-resistant underlayment between the floor finish 302 and intermediate sheathing 306.

In the example subfloor and ceiling structure 400 illustrated in FIG. 4, which does not include intermediate sheathing, the lightweight composite subfloor panels 404 are fastened directly to the floor joists 406 and can advantageously have a relatively thick cross-sectional thickness, such as a thickness of about ½ inch to about 1¼ inch, or about ⅝ inch to about 1 inch, or about ¾ inch. The lightweight composite subfloor panels 304 can have sufficient cross-sectional thickness in order to provide the main load-bearing support structure between the joists 406 and the floor finish 402.

In both embodiments, the lightweight composite ceiling panels 314 in FIGS. 3A-3C and the lightweight composite ceiling panels 408 in FIG. 4 can have an intermediate cross-sectional thickness, such as a thickness of about ⅜ inch to about ¾ inch, or about 7/16 inch to about ⅝ inch, or about ½ inch. The lightweight composite ceiling panels 314, 408 can have sufficient cross-sectional thickness in order to yield a ceiling structure that does not sag and is able to support fixtures typically attached to ceilings, such as lights, chandeliers, and other common ceiling fixtures.

III. Lightweight Composite Panels

The subfloor and optional ceiling structures disclosed herein are made using lightweight composite panels fastened to a subfloor support structure. Lightweight composite subfloor panels can be used to make the main underlayment of a subfloor, and lightweight composite ceiling panels can be used to make an optional ceiling of a lower floor beneath the subfloor. Lightweight composite subfloor and ceiling panels comprise a strong, yet lightweight, polymer or inorganic foam core and fiber reinforced cementitious (or other protective) layer on opposite sides of the foam core. As a result, the lightweight composite panels are water-resistant and lightweight, yet strong and can support relatively heavy loads. Lightweight composite ceiling panels can be modified to include a plaster layer, UV or chemical cured polymer layer, or paper layer adapted to receive a desired ceiling finish.

A. Basic Structure and Manufacture of Lightweight Composite Panels

FIGS. 5A and 5B illustrate basic lightweight composite panels 500a, 500b, 500c of varying cross-sectional thickness. They also show the layered structure of the lightweight composite panels, including strong but lightweight polymer or inorganic foam cores 510a, 510b, 510c sandwiched between first fiber mesh reinforced cementitious layers 520a, 520b, 520c and second fiber mesh reinforced cementitious layer 530a, 530b, 530c. The cross-sectional thickness of the lightweight composite panels 500a, 500b, 500c can be selected based on a combination of desired properties for their intended use, such as if they form a subfloor and main underlayment over intermediate sheathing, or if they are attached directly to the subfloor framework where intermediate sheathing is omitted, or if they are used to form a ceiling structure of a lower floor.

As illustrated in FIGS. 5A and 5B, the cross-sectional thickness of the lightweight composite panels 500a, 500b, 500c varies mostly or entirely depending on the cross-sectional thickness of the foam cores 510a, 510b, 510c. Although not shown, when lightweight composite panels 500a, 500b, 500c of greater cross-sectional thickness are desired, it may be desirable to increase the thickness of the fiber mesh reinforced cementitious layers 520, 530 (e.g., to account for possible strength reduction caused by including a foam core 510 of greater cross sectional thickness).

FIG. 5C is in an exploded view that schematically illustrates the layered structure of a lightweight composite panel 500, which is similar or identical to the lightweight composite panels 500a, 500b, 500c of FIGS. 5A and 5B. The foam core 510 can be a lightweight polymer foam made from closed cell extruded polystyrene (XPS), is lightweight, rigid, and highly water-resistant, and includes two outer surfaces or faces. In some embodiments, the foam core 210 may have a density of about 30-45 kg/m³ and a compressive strength of about 250-400 kPa.

Alternatively, the foam core 510 can be made from a different polymer foam material, such as, but not limited to, expanded polystyrene foam (EPS), polyisocyanurate foam, polyurethane (PUR) foam, phenolic polymer (e.g., phenol-formaldehyde) foam, melamine polymer (e.g., melamine-formaldehyde) foam, and/or other thermoplastic or thermoset polymer known in the art that can be formed into rigid or semi-rigid foam layers. An advantage of thermoset polymer foam materials is they are generally more fire- and heat-resistant than thermoplastic polymers, with thermoset phenolic polymers in particular providing a high level of fire and heat resistance.

The properties of various polymers that can be used to make foam core layers 110, 210 are set forth in Tables 1-3.

TABLE 1
Property	XPS/EPS	Phenolic
Material Type	Thermoplastic	Thermoset (phenol-
	polystyrene	formaldehyde)
Thermal Conductivity	0.028-0.033	0.018-0.022
(W/m · K)
R-Value per inch	~5.0	6.5-7.2
Fire Resistance	Poor - melts, drips	Excellent - chars, low
		smoke
Flame Spread (ASTM E84)	75-200	<25 (Class A)
(W/O Facer
Smoke Development (W/O	>450	<50
Facer)	(often)

Thermal Stability

~93° C. (melts)

150-175°

C.

Water Resistance

Excellent

Good (closed-cell)

Compressive Strength

200-300 kPa

100-150

kPa

Flexural Strength	Flexible, good	Brittle
Recyclability	Yes (thermoplastic)	No
Weight (kg/m3)	25-35	35-50
Cost	Low-Moderate	High

TABLE 2
Property	Melamine	PUR
Material Type	Thermoset (melamine-	Thermoset (polyol +
	formaldehyde)	isocyanate)
Thermal Conductivity	0.032-0.036	0.020-0.025
(W/m · K)
R-Value per inch	~4.1-4.5	~6.0-6.5
Fire Resistance	Excellent - non-	Poor - needs FR
	melting, self-	additives

extinguishing

Flame Spread (ASTM E84)	<25 (Class A)	Varies (often >25)
(W/O Facer
Smoke Development (W/O	Very low	High
Facer)

Thermal Stability

~240° C.

~100-120°

C.

Water Resistance

Poor unless sealed

Good

Compressive Strength

Low

150-300

kPa

Flexural Strength	Very brittle	Strong
Recyclability	Limited	No
Weight (kg/m3)	7-12	30-45
Cost	High	Moderate

	TABLE 3
	Property	Polyiso
	Material Type	Thermoset (polyisocyanurate)
	Thermal Conductivity	0.020-0.023
	(W/m · K)
	R-Value per inch	~6.0-6.5
	Fire Resistance	Good - chars, often Class A
		with facer
	Flame Spread (ASTM E84)	<25 (Class A with facer)
	(W/O Facer
	Smoke Development (W/O	<150
	Facer)

Thermal Stability

~150°

C.

	Water Resistance	Fair (can degrade if
		unprotected)

Compressive Strength

140-200

kPa

	Flexural Strength	Moderate
	Recyclability	Rarely recycled
	Weight (kg/m3)	30-42
	Cost	Moderate-High

With reference to FIG. 5, formed over first and second outer surfaces of the foam core 510 are first and second layers of fiber (e.g., fiberglass) mesh 520b, 530b, respectively, which become embedded within respective first and second layers of fresh cementitious composition applied over the fiber mesh layers 520b, 530b, which harden or cure to form first and second cementitious layers 520a, 530a. Together, the hardened cementitious layers 520a, 530a and embedded fiberglass mesh layers 520b, 530b form first and second fiber mesh reinforced cementitious layers 520, 530, which adhere to the foam core 510 to form a strong but lightweight composite panel structure. The fiber mesh layers 520b, 530b can alternatively include other fibers or filaments, such as carbon fibers or filaments.

The lightweight foam core is typically made from extruded polystyrene foam (XPS), but can alternately comprise expanded polystyrene foam (EPS), polyisocyanurate foam, polyurethane (PUR) foam, phenolic polymer (e.g., phenol-formaldehyde) foam, melamine polymer (e.g., melamine-formaldehyde) foam, and/or other thermoplastic or thermoset polymer known in the art that can be formed into rigid or semi-rigid foam layers. The lightweight foam core can be made of closed cell polystyrene foam to provide a water-resistant barrier (e.g., 100% waterproof).

Alternatively, the foam core may comprise an inorganic foam, such as a refractory foam material, to provide additional fire-resistance. Examples include silica gel, aerogel, silicate foams, urea-silicate foam, SiOC/SiC, ceramic foams, refractory foams, and the like. The inorganic foam core can resist melting even when exposed to fire or intense heat in order for the lightweight composite panel to maintain its structural integrity.

In some embodiments, lightweight composite panels are manufactured by applying a fiber (e.g., fiberglass) mesh and fresh cementitious composition onto first and second surfaces of a rigid polymer (e.g., XPS) or inorganic foam core and causing or allowing the applied cementitious composition to harden. The fiber mesh becomes embedded in the hardened cementitious layer to enhance strength, increase toughness, and prevent cracking of the hardened cementitious layer. Alternatively, at least one of the hardened cementitious layers can be replaced or augmented with a UV or chemical cured polymer layer.

The layers of fiber mesh reinforced cementitious composition are generally “thin” (e.g., typically less than about 3 mm, less than about 2.5 mm, less than about 2 mm, or less than about 1.5 mm, such as about 1 mm, or between about 0.5-3 mm, about 0.75-2.5 mm, about 1-2 mm, or about 1.25-1.75 mm in cross-sectional thickness). The fiber mesh reinforced cementitious layers can be very lightweight yet waterproof and have high structural strength (i.e., high tensile and flexural strength and high toughness). The fiber mesh component is typically fiberglass fiber or glass filament mesh, but can be made of other strong fibers or filaments, such as carbon fibers or filaments. In some embodiments, fiberglass mesh is formed of an alkali-resistant material and may have nominal mesh size of 4×4 mm with a strand diameter of about 0.5-1.0 mm.

In the case where it is desired for lightweight composite panels to have beveled edges (e.g., to accommodate mesh tape and floor or ceiling patch to join adjacent lightweight composite panels together), the fiber mesh reinforced cementitious layer can be applied before or after forming beveled edges in the polymer form core when forming the composite structure, preferably after forming beveled edges to create a continuous fiber mesh reinforced cementitious layer across the entire surface of the lightweight composite panel.

In some embodiments, the fresh cementitious composition comprises mixture products of water, hydraulic cement, silicon dioxide powder, calcium oxide, iron oxide, plaster of Paris (gypsum hemihydrate), water-reducing agent, defoamer, styrene, and acrylic acid. The fresh cementitious composition may optionally include supplementary cementitious materials (SCMs), such as ground granulated blast furnace slag (GGBFS), fly ash, natural pozzolan, silica fume, microsilica, metakaoline, ground glass, calcined clay, finely ground quartz, limestone powder, and the like. The cementitious composition may include other components, such as natural hydraulic lime, calcium silicate, and/or expanded glass, which can increase fire and heat resistance.

In a more particular embodiment, the cementitious composition applied to the outer surfaces of the foam core to form fiber mesh reinforced cementitious layers of the lightweight composite panel structures can be formed by mixing together the following components (expressed in weight percent) to form a fresh flowable cementitious composition, which is applied to the foam core surfaces, together with fiber mesh, and then allowed to harden or cure:

	Hydraulic cement	30-50%
	Silicon dioxide	40-60%
	Calcium oxide	2-5%
	Iron oxide	0.2-1%
	Gypsum hemihydrate	3-8%
	Water-reducing agent	0.2-0.6%
	Defoamer	0.2-0.6%
	Styrene	1-2%
	Acrylic acid	1-2%
	Water	(16-20%, preferably 18.4%
		dry ingredients above)

The hydraulic cement typically includes Portland cement clinker interground with gypsum for set control, but may also include other interground minerals, such as limestone filler (e.g., 5-10% by weight of the hydraulic cement), and optionally one or more supplementary cementitious materials (SCMs), such as ground granulated blast furnace slag (GGBFS), fly ash, natural pozzolan, silica fume, microsilica, metakaoline, ground glass, calcined clay, finely ground quartz, and the like. The silicon dioxide can be 150 mesh ground quartz sand. The water reducer can be a low-range water reducer, such as a compound of carboxylic acid grafted multi-polymer and other effective additives. The defoamer can reduce the surface tension of water, solution, suspension, etc., prevent the formation of foam, or reduce or eliminate the original foam. The main component of the defoamer can be polydimethylsiloxane (Me₃SiO(Me₂SiO)nSiMe₃) (Me=methyl). In the case where very fine SCMs (e.g., silica fume, microsilica, or metakaoline), it may be desirable to use a high range water reducer (e.g., polycarboxylate ether) to obtain good flow. The styrene and acrylic acid components, which may be a copolymer, can form a chemical bond to the extruded polystyrene foam core, in addition to the physical bond.

The components of the cementitious composition can be mixed by high-performance mixing equipment through precise batching, and then fed into a mixing barrel in sequence for high-speed dispersion and mixing, thus yielding a fresh cementitious mixture. The fresh cementitious mixture is blended in a tank to make it into liquid or plastic form. The liquid cementitious mixture is then pumped into a machine variously called a “waterfall machine,” commonly known as a “curtain coater” or enrobing “coater/machine”, which has flow control of the liquid cementitious mixture and which will apply the liquid cementitious mixture onto surfaces of an extruded polystyrene foam sheet or other material to be coated. The liquid cementitious mixture is applied like a waterfall or curtain through a blade applicator to evenly apply it to the polymer foam surfaces or other surface to be coated. The product is then UV or chemical cured and left to stand for approximately 7 days as usual practice. However, if ambient conditions are dry and hot, the curing period could be shortened to approximately 3-4 days.

In general, the hardened fiber mesh reinforced cementitious composition can adhere and bond strongly to the polymer or inorganic foam core to form a strong lightweight composite panel structure that does not delaminate. The bond between the cementitious layers and the foam layer is likely a combination of physical and chemical interactions. When applied to the polymer or inorganic foam layer, the liquid cementitious composition can penetrate into surface pores of the foam layer, which upon hardening of the cementitious composition, forms a strong mechanical bond. This bond can be further enhanced through the inclusion of very fine pozzolans, such as silica fume, microsilica, or metakaoline on the cementitious composition, which creates a very high strength cementitious layer and are able to fill very small micropores. The polymer components of the cementitious composition may also interact with components of the foam layer to form a type of chemical bond between the cementitious layers and the foam (e.g., polymer) layer. Regardless of how bonding occurs, it is demonstrably very strong and does not delaminate during specified use. Curable resins also adhere and bond strongly to the foam core.

In some embodiments, when manufacturing the lightweight composite panels, the fiberglass mesh is first laid down on a polymer (e.g., extruded polystyrene) or inorganic foam sheet. A transportation belt then transports the foam sheet with the fiberglass mesh through the waterfall machine (commonly known as a “curtain coater” or enrobing “coater/machine”), which causes the liquid cementitious mixture to flow down like a waterfall or curtain, with control of the liquid cementitious mixture flow, onto the foam sheet or other substrate. In this way, the fiberglass mesh becomes embedded in the liquid cementitious mixture and essentially floats in the middle of the cementitious mixture. In other words, a portion of the liquid cementitious mixture will be positioned between the fiberglass mesh and the foam sheet in order to directly adhere to the foam sheet, and another portion of the liquid cementitious mixture will cover and encapsulate the fiber mesh to form the top surface of the core composite tile structure. The result is a layered composite panel structure, with an interior polymer or inorganic foam sheet, an underlying layer of cementitious composition in direct contact with the foam sheet, a fiberglass mesh in the middle, and a top layer of cementitious composition covering the fiberglass mesh.

In addition to, or instead of, a fiber mesh reinformed cementitious layer, one or both protective layers of the composite core panel structure may comprise other materials in addition to or instead of the cementitious composition. Examples include one or more of rigid magnesium oxide material, water-resistant polymer, or a composite material comprising a resin or polymer with embedded fibers, fiber mesh, fabric, scrim, felt, or non-woven. The material forming the fibers, fiber mesh, fabric, scrim, felt, or non-woven can be selected from plant fibers, polymer fibers, and inorganic fibers (e.g., basalt, rock wool, and the like). The resin or polymer may comprise a thermoplastic or thermoset material, such as UV-cured resins, polypropylene, polycarbonate, polyethylene terephthalate, polystyrene, acrylate, methacrylate, polyurea, polyaspartic, or epoxy. Protective layers of thermoset polymer can be slightly thicker than fiber mesh reinforced cementitious layers, such as between about 1-5 mm or about 2-3 mm.

Polyurea is a type of elastomer that is derived from the reaction product of an isocyanate component and an amine component. The isocyanate can be aromatic or aliphatic in nature. It can be monomer, polymer, or any variant reaction of isocyanates, quasi-prepolymer or a prepolymer. The prepolymer, or quasi-prepolymer, can be made of an amine-terminated polymer resin, or a hydroxyl-terminated polymer resin. The resin blend can include amine-terminated polymer resins and/or amine-terminated chain extenders. The resin blend may also contain additives or non-primary components, such as pigments pre-dispersed in a polyol carrier. Normally, the resin blend does not contain a catalyst. This is because the reaction between an isocyanate and amine is extremely fast and hence does not need catalysis.

The chemical structure of polyurea is as follows:

In a polyurea, alternating monomer units of isocyanates and amines react with each other to form urea linkages, as shown below.

Polyaspartic resin is a solvent-free, aliphatic amine coating material based on aspartic acid, polyaspartic acid, or polyaspartic ester, which reacts with an isocyanate to create extremely durable protective coatings with rapid cure times, excellent abrasion resistance. An example of a curable polyaspartic resin has the following reactants and final cured polymer structure:

The curable resin can be applied by spray coating while in a flowable state to one or both surfaces of the foam core and allowing it to cure and form a solid protective layer. Multiple parts of the curable resin can be mixed just prior to entering or within the nozzle used to spray coat the foam core. Where it is desired to incorporate a fiberglass mesh sheet in the polymer layer, an initial coating of curable resin can be applied to the foam core, followed by applying the fiberglass mesh sheet over the resin, followed by applying a final coating of the curable resin.

In some embodiments, the fiber mesh reinforced cementitious layers of the lightweight composite panels can have a grid-like pattern or texture (or other uneven pattern) that can facilitate adhesion of structural and/or decorative materials thereto, such as floor joists, beams, furring strips, insulating foam boards, intermediate sheathing panels, and floor finishes. Nevertheless, it may be desirable to apply patches of an appropriate seam coat (e.g., thin set mortar or fine-sanded stucco) to cover screws, sealants, holes, or other discontinuities prior to applying a floor finish. Mesh tape can be used to join adjacent lightweight composite panels together with appropriate fasteners and a seam coat over the top.

The lightweight composite panels can be fastened to a subfloor support structure using fasteners known in the art, such as screws, rivets, adhesives, and other fastening means. In some embodiments, an adhesive, such as construction adhesive, can be used to adhere lightweight composite subfloor panels to the subfloor support structure, including to intermediate sheathing or directly to a subfloor framework, either in addition to or instead of screws or other mechanical fasteners. An adhesive can provide a more continuous bond interface between lightweight composite panels and joists, beams, furring strips, or intermediate sheathing, thereby distributing the load more evenly and improving shear strength of the subfloor and prevent floor creaking. The use of adhesives in addition to or instead of screws can eliminate discrete attachment points, creating a more solid and continuous bond that can better resist lateral forces and improve strength of the subfloor structure.

B. Lightweight Composite Plaster Panels

In order for lightweight composite panels to function more effectively as a ceiling structure (e.g., similar to traditional drywall panels), such as where it may be desired to apply an interior finish, such as paint, wallpaper, or crown molding, lightweight composite panels can be modified to include a plaster layer applied over at least one fiber mesh reinforced cementitious (or other protective) layer. The plaster layer can be generally white in color (although other colors are possible if desired). U.S. Provisional Application Nos. 63/686,489 and 63/692,563, incorporated by reference, disclose a version of lightweight composite plaster panels that can be used to construct a ceiling beneath a subfloor structure.

Lightweight composite plaster panels can include a light colored (e.g., white or off white) plaster layer bonded over at least the exterior fiber mesh reinforced cementitious (or other protective) layer, and optionally the side edges, giving the lightweight composite plaster panels the appearance of plaster board without paper. Because lightweight composite plaster panels include fiber mesh reinforced cementitious (or other protective) layers, along with a waterproof interior polymer or inorganic foam core, they are fire and heat resistant, waterproof, resistant to mold growth, and substantially stronger than conventional gypsum board. Lightweight composite plaster panels can be used, for example, in embodiments where the subfloor separates upper and lower floors, and where a ceiling is attached beneath the subfloor and a floor finish is attached over the subfloor.

The lightweight composite plaster panels can have the same interior structure as basic lightweight composite panels discussed above, including a strong, yet lightweight polymer or inorganic foam core sandwiched between two fiber mesh reinforced cementitious (or other protective) layers, but with an additional plaster coating applied on at least one fiber reinforced cementitious (or other protective) layer to provide a plaster finish. The plaster layer can be textured, sanded, painted, wallpapered, and the like, similar to the surface of conventional gypsum panels. The lightweight composite plaster panels can be attached to joists, beams, furring strips, and/or foam panels using screws, rivets, nails, adhesives, or other known attachment means. The lightweight composite plaster panels can also include bevels (e.g., 2 or 4) to permit placement of multiple adjacent lightweight composite plaster panels, followed by application of wall patch (taping and mudding) to hide the joints. Specialized connectors, such as washers with enlarged surfaces and penetrating prongs can be used to join adjacent lightweight composite plaster panels together.

Reference is made to FIGS. 6A-6F, which illustrate example embodiments of lightweight composite plaster panels FIG. 6A illustrates the layered structure of an example lightweight composite plaster panel 600. The lightweight composite plaster panel 600 comprises a basic lightweight composite panel structure, including a foam core 610 sandwiched between a first fiber mesh reinforced cementitious (or other protective) layer 620 and a second fiber mesh reinforced cementitious (or other protective) layer 630. A plaster layer 632 is formed over the second fiber mesh reinforced cementitious (or other protective) layer 630, which forms the side that will be visible as a show wall surface (at least before a finish is applied to the plaster layer 632). The first fiber mesh reinforced cementitious (or other protective) layer 620 does not include a plaster layer and faces toward the subfloor framework. The first fiber mesh reinforced cementitious (or other protective) layer 620 has a textured surface that can facilitate adhesion where an adhesive is used to attach the lightweight composite plaster panel 600 to a subfloor support structure. In addition, the first and second fiber mesh reinforced cementitious (or other protective) layers 620, 630 provide high strength, which permits the lightweight composite plaster panel 600 to support relatively heavy loads, such as pictures, television sets, or other appliances using nails or screws, particularly if they can penetrate through both the first and second fiber mesh reinforced cementitious (or other protective) layers 620, 630.

FIG. 6B illustrate two lightweight composite plaster panels 600a, 600b positioned side-by-side and abutting each other, with beveled edges 610a, 610b aligned so as to permit the application of tape and wall patch to join them together, as illustrated in FIG. 6C. FIG. 6B shows the beveled edges 610a, 610b covered by a portion of the plaster layer 632, FIG. 6C shows the beveled edges 610a, 610b hidden beneath a plaster coating (e.g., drywall patch) such that the two lightweight composite plaster panels 700a, 700b have been joined together to yield a finished, seamless plaster surface finish 632.

FIG. 6D is a side cross-sectional view, and FIG. 6E is an exploded view, of an example lightweight composite plaster panel 600 having a layered structure. As shown in FIG. 6D, the lightweight composite plaster panel 600 includes a polymer or inorganic foam core 610, a first fiber mesh reinforced cementitious (or other protective) layer 620, a second fiber mesh reinforced cementitious (or other protective) layer 630, and a plaster layer 632 formed over the second fiber mesh reinforced cementitious (or other protective) layer 630. In this embodiment, the lightweight composite plaster panel 600 also includes beveled edges 634, with the foam core 610 being covered by a portion of the second fiber mesh reinforced cementitious layer 620, which in turn is covered by a portion of the plaster layer 632. In this way, the beveled edges 634 have similar strength as the main portion of the lightweight composite plaster panel 600, which permits using screws, rivets, or other fastening means to fasten the lightweight composite plaster panel 600 to a subfloor support structure through the beveled edges 634.

FIG. 6E is an exploded view of the lightweight composite plaster panel 600 that more particularly illustrates the layered structure. The lightweight composite plaster panel 600 includes a polymer or inorganic foam core 610, a first fiber mesh reinforced cementitious layer 620, which includes a first cementitious layer 620a with embedded first fiberglass mesh 620b, a second fiber mesh reinforced cementitious layer 630, which includes a second cementitious layer 630a with embedded second fiberglass mesh 630b, and a plaster layer 632 formed over the second fiber mesh reinforced cementitious layer 630. The lightweight composite plaster panel 600 also includes beveled edges 634, which includes a portion of the foam core 610 covered by a portion of the second fiber mesh reinforced cementitious layer 630, which in turn is covered by a portion of the plaster layer 632.

FIG. 6F schematically illustrates a lightweight composite plaster panel 600 having beveled edges 634 in each of the four sides, and a plaster layer 632 covering the entire upper surface, four beveled edges 634, the four side ends. The plaster layer 632 of the beveled edges 634 is applied over the portions of the second fiber mesh reinforced cementitious layer 630 (not shown) that extend over the foam core 610 (not shown) in the region of the beveled edges 634 to provide the beveled edges 634 with additional strength.

In some embodiments, a fresh plaster composition used to form the plaster layer comprises mixture products of water, hydraulic cement, preferably white cement, calcium carbonate, aluminum oxide, silicon dioxide, cellulose ether, and latex. The fresh plaster composition may optionally include supplementary cementitious materials (SCMs), such as ground granulated blast furnace slag (GGBFS), fly ash, natural pozzolan, silica fume, microsilica, metakaoline, ground glass, calcined clay, finely ground quartz, limestone powder, and the like. The cementitious composition may include other components, such as natural hydraulic lime, calcium silicate, and/or expanded glass, which can increase fire and heat resistance.

In some embodiments, a plaster composition used to form the plaster layer 632 over at least one of the first and second fiber mesh reinforced cementitious layers 620, 630 and over beveled edges of a basic lightweight composite panel can be made by mixing together the following components (expressed in weight percent) to form a fresh, flowable cementitious composition:

Hydraulic cement	30-50%
Calcium carbonate	40-70%
Aluminum oxide (Al2O3)	1-3%
Silicon dioxide	4-8%
Calcium oxide	2-5%
Hydroxypropyl methylcellulose	0.2-06%
Latex powder	2-4%
Water	(0.5 to 1.5, or 0.75 to 1.25, or 1 part
	water per 2.5 parts of dry ingredients)

The hydraulic cement typically includes Portland cement, preferably white cement for aesthetic reasons, but may also include supplementary cementitious materials (SCMs), such as ground granulated blast furnace slag (GGBFS), fly ash, natural pozzolan, silica fume, microsilica, metakaoline, ground glass, calcined clay, finely ground quartz, and the like. The Portland cement comprises ground cement clinker interground with gypsum for set control and limestone as a filler. For aesthetic reasons, SCMs, when included, are preferably white or light colored. The silicon dioxide can be 150 mesh ground quartz sand. The latex powder can be redispersible 558 latex, which can be an ethylene/vinyl acetate copolymer, vinyl acetate/versatate copolymer, acrylic copolymer, etc. The latex powder can improve adhesion of the plaster layer to a cementitious layer.

The dry components of the plaster composition, known euphemistically as “putty powder”, can be dry mixed in a mixer to form an evenly mixed dry blend. Then the water is added to the mixture to form a fresh flowable plaster composition that can be sprayed. A spray gun is used to apply the fresh plaster composition to the fiber mesh reinforced cementitious layer of a basic lightweight composite wallboard (e.g., with or without beveled edges). The amount of plaster composition applied should be sufficient to cover the fiber mesh reinforced cementitious layer so that the grid-like texture is no longer visible, forming a smooth surface (or surface having a desired texture). The plaster composition is then allowed to cure for 7 days to form a hardened surface, which can be polished if desired to yield a smooth surface.

In some embodiments it may be desirable to cut the beveled edges to a width of about 1.5 inches (e.g., 1-2 inches, or 1.25-1.75 inches). If any portion of the composite plaster panels includes exposed expanded polystyrene foam, a primer can be used to cover the exposed polystyrene foam to enhance strength and improved the bond of drywall patch to the composite plaster panels.

In some embodiments, it may be desirable to apply and finish the plaster layer in a manner that provides what is known in the industry as “level 5” finish, or “drywall finish level 5”. A level 5 finish is defined by the Gypsum Association, the trade association for drywall professionals. The Gypsum Association has codified a set of professional standards that define the process of finishing drywall into five distinct levels. The following definitions are given for comparison. A level 0 finish means that no drywall finishing of any type has been done. At this level, the drywall panels are simply fastened to the walls or ceiling. A level 1 finish means that drywall joint tape has been embedded in the joint compound at the seams or joints, with no further finishing. A level 2 finish means that a skim coat of joint compound has been applied over the tape and to cover drywall screw holes. A level 3 finish means that a drywall finisher has applied a coat of joint compound to the tape and screws. Walls that will receive a heavy texture can end at this level, as progressing beyond this level of smoothness is unnecessary since texturing will produce a finish that is rougher than level 3. A level 4 finish is the classic drywall finish. This is achieved by applying another coat of joint compound to the tape and screws and sanding the dried compound. A level 4 finish is typically used when a surface is painted or covered with wallpaper. A level 5 finish is the highest possible level of drywall finishing and involves applying a skim coat, if applicable. A level 5 finish is achieved by applying another skim coat of joint compound (or mud) to a level 4 finish and then fine sanded. A level 5 finish is desirable when the applied finish will have glossy, enamel, or non-textured flat paint or when the light will be angled low enough to highlight bumps and depressions.

A level 5 finish is a premium finish that typically commands a much higher cost than lower level finishes. Providing a lightweight composite drywall panel having a plaster coating that already provides a level 5 finish can eliminate the many steps and time required to prepare ordinary drywall to have a level 5 finish. This saves labor costs and time, including the time required for each coat of joint compound to dry and then be sanded.

C. Lightweight Laminated Composite Ceiling Panels

Other versions of lightweight composite ceiling panels that can be used to form a ceiling underneath a subfloor that separates upper and lower floors are disclosed in U.S. Provisional Application No. 63/703,834, incorporated by reference, and includes an exterior paper layer instead of a plaster layer positioned over and/or bonded to a fiber mesh reinforced cementitious (or other protective) layer of a basic lightweight composite panel as disclosed herein. The paper can be impregnated or treated with a waterproofing material, such as wax or silicone, to yield waterproof paper.

Alternatively, the lightweight laminated composite ceiling panel can include an exterior polymer layer instead of, or in addition to, the paper layer to provide enhanced waterproofing. Examples of polymer films or sheets that can be used to form the polymer layer include, but are not limited to, polyvinyl chloride (PVC), polyethylene (PE), polycarbonate (PC), polypropylene (PP), and polyester (PES). U.S. Provisional Application No. 63/788,276, incorporated by reference, discloses lightweight composite panels that include a UV or chemical cured polymer finish layer, which can have a similar appearance as the lightweight composite plaster panels described above. In some embodiments, the UV or chemical cured polymer finish layer can be the same or similar composition used to adhere a paper layer over a core composite structure described in this section.

FIGS. 7A and 7B illustrate an example embodiment of a lightweight laminated composite ceiling panel 700. FIG. 7A is an exploded view and FIG. 7B is a side cross-section view of the lightweight laminated composite ceiling panel 700. FIG. 7A illustrates a first fiberglass mesh sheet 750 that becomes embedded within with a first cementitious layer 720 and a second fiberglass mesh sheet 740 that becomes embedded within with a second cementitious layer 730 to form fiber mesh reinforced cementitious layers.

FIG. 7A more particularly shows the first and second fiberglass mesh sheets 750, 740 and first and second cementitious layers 720, 730 extending over the entirety of a polymer or inorganic foam core 710, including the beveled edges, to provide added strength over the entirety of the laminated lightweight composite drywall panel 700, including in the region of the beveled edges. FIG. 7B also shows the second fiber mesh reinforced cementitious layer 730 covering an entire surface of the foam core 710, including the beveled edges 734. FIGS. 7A and 7B show a paper (or cured polymer) layer 732 covering the second fiber mesh reinforced cementitious layer 730, including the beveled edges 734, wrapping around the ends, and covering a portion of the first fiber mesh reinforced cementitious layer 720. This creates a more secure bond that helps prevent delamination of the paper (or cured polymer) layer 732.

Because the core structure of the laminated lightweight composite ceiling panel 700 comprises a strong lightweight foam core 710 sandwiched between two fiber mesh reinforced cementitious layers 720, 730, and because the paper or cured polymer laminated onto the core lightweight composite structure is lightweight, the laminated composite ceiling panel 700 is lighter and stronger than conventional gypsum panels. Moreover, the lightweight composite panel structure is waterproof, providing extra safety if a laminated composite ceiling panel 700 is inadvertently exposed to water. Even if a non-waterproof paper layer 732 is damaged, the structural integrity of the panel structure is maintained and not compromised like traditional gypsum panels. Moreover, the paper layer 732 can include a waterproofing material on or in the paper to protect the paper layer 732 from moisture damage and absorption of deleterious substances and contaminants. Alternatively, the paper layer 732 can be replaced or augmented with a UV or chemical cured polymer layer.

The laminated composite drywall panel 700 advantageously includes beveled edges (e.g., 2 or 4) to permit placement of multiple adjacent lightweight laminated composite ceiling panels beneath a subfloor support structure to form beveled joints, followed by application of ceiling patch (taping and mudding) to hide the beveled joints.

In some embodiments, the fiber mesh reinforced cementitious layer of the core composite structure over which the paper or curable polymer layer is applied can have a grid pattern or other discontinuity that may be desirably smoothed out prior to applying the paper or curable polymer layer in order to yield a laminated composite ceiling panel having a smooth surface, at least on the exposed side that is intended to receive a surface finish. This can be done by applying a curable composition, such as a UV curable composition, over one or both fiber mesh reinforced cementitious layers of the core composite structure.

Methods and systems for manufacturing lightweight laminated composite ceiling panels are disclosed in U.S. Provisional Application Nos. 63/703,834 and 63/788,276, incorporated by reference. In some embodiments, a UV curable composition applied to one or more fiber mesh reinforced cementitious layers to form a smooth surface comprises mixture products of acrylic resin, acrylic monomer, filler, and initiator. By way of example, the UV curable composition may comprise about 30% to about 90% by weight of one or more acrylic resins, about 10% to about 40% by weight of one or more acrylic monomers, about 10% to about 35% by weight of one or more fillers, and about 1% to about 10% by weight of one or more initiators.

IV. Fastening Lightweight Composite Panels to A Subfloor Support Structure

In some embodiments, screws, rivets, or other fasteners used to attach lightweight composite subfloor panels to a subfloor support structure include corresponding washers or enlarged heads also known as pan head screws or screws with integrated washers that are at least about 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, or 80 mm, in diameter. This ensures sufficiently large surface contact between the screws or other fasteners and the fiber mesh reinforced cementitious (or other protective) layer so that the screws or other fasteners have a much lower tendency to tear through the lightweight composite panels or otherwise compromise the structural integrity of the subfloor structure formed using lightweight composite panels, therefore providing a higher pull-out force . . .

To illustrate this point, FIG. 8 is a photograph of a lightweight composite panel 800 with holes formed by screws 810 passing all the way through the exterior fiber mesh reinforced cementitious layer. Remnants of fiber mesh 820 of the damaged fiber mesh reinforced cementitious layer can be seen. The holes were the result of screw heads being too small (i.e., having too little surface area) to prevent the screws 810 and screw heads from perforating and penetrating all the all the way through the exterior fiber mesh reinforced cementitious layer. FIG. 8 further illustrates a screw 810 with a washer 830 abutting the surface of the lightweight composite panel 800 without having passed through the exterior fiber mesh reinforced cementitious layer.

Reference is now made to FIGS. 9A-9D, which illustrate the use of specialized washers with enlarged surface areas and penetrating prongs that help fix the washers in place relative to the lightweight composite panels, prevent rotation when screws are being driven into joists, beams, furring strips, sheathing, or other structural elements of a subfloor support structure, and add additional lateral strength between the washers and the lightweight composite panels. The penetrating prongs can also be designed to abut the underlying joist, sheathing, or other structural element and act as a stop to prevent the washers from being driven too far into the lightweight composite panel and undesirably crushing or fracturing the exterior fiber mesh reinforced cementitious (or other protective) layer, which could reduce strength of the subfloor and/or ceiling structure.

FIG. 9A more particularly illustrates the use of screws 905 and specialized washers 910 having a plurality of penetrating prongs 920. The specialized washers 910 are rectangular in shape in order to overlap the end surfaces of adjacent lightweight composite panels 900a, 900b. The penetrating prongs 920 penetrate through and become embedded within the lightweight composite panels 900a, 900b, including though the exterior fiber mesh reinforced layers and at least partially through the foam cores of the lightweight composite panels 900a, 900b. The penetrating prongs 920 hold the specialized washers 910 in a desired position relative to the lightweight composite panels 900a, 900b and prevent rotation while the screws 905 are being driven into the lightweight composite panels 900a, 900b and into an underlying joist 925 or other structural elements of a subfloor support structure. The penetrating prongs 920 thereby ensure that left and right wings of the specialized washers 910 reliably overlap corresponding surfaces of the left and right lightweight composite panels 900a, 900b to tie them together. The penetrating prongs 920 can also provide a load spreading/pressure spreading effect, i.e., the prongs 920 distribute the normal and lateral pressure from the screw 905 to the prongs. The specialized washers 910 and penetrating prongs 920 provide greater lateral tension of the screw and washer ensemble relative to the lightweight composite panels 900a, 900b, thereby increasing the overall strength of the subfloor and/or ceiling structure.

FIGS. 9B-9D are photographs that illustrate a specialized washer 930 having a circular shape, although it will be appreciated that the specialized washer can have a rectangular shape, similar to specialized washers 910 illustrated in FIG. 9A, or have other shapes designed to increased lateral overlap of the washers to adjacent lightweight composite panels. FIGS. 9B and 9C more particularly illustrate example penetrating prongs 920 that are designed to penetrate at least partially through the lightweight composite panels 900. FIG. 9D shows the upper surface of a washer 930 having a countersink 960 that accommodates the head of the screw 905 so that the head does not protrude beyond the surface of the circular washer 930 when driven into sheathing or subfloor framework of a subfloor support structure.

As illustrated in FIG. 9B, the penetrating prongs 920 can penetrate through the exterior fiber mesh reinforced cementitious layer 925 and at least partially through the foam core 915 when driven into a subfloor support structure using a screw 905. In this embodiment, the screw 905 is shown driven into an OSB board 935, although it is understood that a subfloor support structure may or may not include the OSB board 935.

The penetrating prongs 920 can advantageously have a length in order to penetrate all the way through the lightweight composite panels 900 and make contact with a subfloor support structure. In this way the penetrating prongs 920 can act as a stop that limits how far the specialized washers 910, 930 can be driven toward and into the lightweight composite panels 900. Providing a stop prevents the specialized washers 910, 930 from being driven too far into the lightweight composite panels 900, thereby preserving the structural integrity and strength of the exterior fiber mesh reinforced cementitious layer 925 adjacent to the specialized washers 910, 930. This preserves and maximizes the overall strength, including shear strength, of the subfloor. The length of the penetrating prongs 920 can be approximately equal to or less than the cross-sectional thickness of the lightweight composite panels 900. In some embodiments, it may be desirable for the length of the penetrating prongs 920 to be slightly less than the cross-sectional thickness of the lightweight composite panels 900 in order to superficially compress, but not damage, the exterior fiber mesh reinforced cementitious layer 925 toward the foam core 915 to thereby increase the compressive force of the washer 910, 930 bearing against the lightweight composite panels 900. This can increase the overall fixation strength of the screw and washer ensemble.

In some embodiments, an appropriate seam coat can be applied over at least a portion of the lightweight composite panels, including over any exposed screws, washers, or other mechanical fasteners used to attach the lightweight composite panels to the subfloor support structure, and over any joints or seams, fiber mesh tape, polyurethane, or other exposed sealants on or in the subfloor structure.

Additional Terms & Definitions

While certain embodiments of the present disclosure have been described in detail, with reference to specific configurations, parameters, components, elements, etcetera, the descriptions are illustrative and are not to be construed as limiting the scope of the claimed invention.

Furthermore, it should be understood that for any given element of component of a described embodiment, any of the possible alternatives listed for that element or component may generally be used individually or in combination with one another, unless implicitly or explicitly stated otherwise.

In addition, unless otherwise indicated, numbers expressing quantities, constituents, distances, or other measurements used in the specification and claims are to be understood as optionally being modified by the term “about” or its synonyms. When the terms “about,” “approximately,” “substantially,” or the like are used in conjunction with a stated amount, value, or condition, it may be taken to mean an amount, value or condition that deviates by less than 20%, less than 10%, less than 5%, less than 1%, less than 0.1%, or less than 0.01% of the stated amount, value, or condition. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Any headings and subheadings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims.

It will also be noted that, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” do not exclude plural referents unless the context clearly dictates otherwise. Thus, for example, an embodiment referencing a singular referent (e.g., “widget”) may also include two or more such referents.

It will also be appreciated that embodiments described herein may also include properties and/or features (e.g., ingredients, components, members, elements, parts, and/or portions) described in one or more separate embodiments and are not necessarily limited strictly to the features expressly described for that particular embodiment. Accordingly, the various features of a given embodiment can be combined with and/or incorporated into other embodiments of the present disclosure. Thus, disclosure of certain features relative to a specific embodiment of the present disclosure should not be construed as limiting application or inclusion of said features to the specific embodiment. Rather, it will be appreciated that other embodiments can also include such features.