Head-of-wall fireblock systems and related wall assemblies

Abstract

A fire retardant head-of-wall assembly configured to seal a linear head-of-wall construction joint or gap when exposed to a heat source such as a building fire is disclosed. The inventive fire retardant head-of-wall assembly comprises a header track having an elongated intumescent strip affixed lengthwise on at least one of the outer sidewall surfaces of the header track and above a centrally located and outwardly protruding lengthwise corrugated groove. The intumescent strip comprises expandable graphite and a fire retardant (C2-C8 alkyl diamine phosphate). When exposed to a heat source such as a building fire, the intumescent strip expands so to fill the head-of-wall construction joint or gap, thereby retarding or preventing the spread of smoke and fire. The inventive fire retardant head-of-wall assembly has been certified as complaint with respect to Underwriters Laboratories, Inc.'s standards set forth in its Tests for Fire Resistance of Building Joint Systems—UL 2079.

Description

TECHNICAL FIELD

The present invention relates generally to fire blocking and containment systems used in the construction of buildings and, more particularly, to fireblocks and fire blocking systems used to seal static and dynamic head-of-wall construction joints and gaps, as well as other mechanical, electrical, plumbing (MEP) penetrations commonly associated with wall construction and assemblies.

BACKGROUND OF THE INVENTION

Metal framing assemblies used to construct commercial and residential buildings are common in the building construction arts. These metal framing assemblies are generally constructed from a plurality of metal framing members including studs, joists, trusses, and other metal posts and beams formed from sheet metal and frequently fabricated to have the same general cross-sectional dimensions as standard wood members used for similar purposes. Metal framing members are typically constructed by roll-forming 12 to 24 gauge galvanized sheet steel. Although many cross-sectional shapes are available, the primary shapes used in building construction are C-shaped studs and U-shaped tracks.

In the building construction trade, a head-of-wall joint (also sometimes referred to as a top-of-wall joint) refers to the linear junction or interface existing between a top section of a framing/wallboard wall assembly and the ceiling (where the ceiling may be a next-level floor or corrugated pan roof deck, for example). Head-of-wall joints often present a serious challenge in terms of reducing or preventing the spread of smoke and fire during a building fire. In this regard and in common practice, a wall to ceiling connection of many newly constructed buildings consists essentially of an inverted U-shaped elongated steel channel (or track) configured to receive steel studs between the legs of the shaped channel. A wallboard is generally attached to at least one side of the studs. The studs and wallboard are in many instances spaced apart from the ceiling a short gap distance in order to allow for ceiling deflections caused by seismic activity or moving overhead loads. Channel and stud assemblies that allow for ceiling deflections are commonly referred to as dynamic head-of-wall systems. Exemplary steel stud wall constructions may be found in U.S. Pat. Nos. 4,854,096 and 4,805,364 both to Smolik, and U.S. Pat. No. 5,127,203 to Paquette. Exemplary dynamic head-of-wall systems having steel stud wall constructions may be found in U.S. Pat. No. 5,127,760 to Brady, and U.S. Pat. No. 6,748,705 to Orszulak et al.

In order to contain the spread of smoke and fire, a fire resistant material such as, for example, mineral wool is often times stuffed into the gaps between the ceiling and wallboard (see, e.g., U.S. Pat. No. 5,913,788 to Herren). For example, mineral wool is often stuffed between a steel header track (e.g., an elongated U-shaped channel) and a corrugated steel roof deck (used in many types of steel and concrete building constructions); a fire resistant and generally elastomeric spray coating is then applied onto the exposed mineral wool to thereby form a fire resistant joint seal (see, e.g., U.S. Pat. No. 7,240,905 to Stahl). In certain situations where the ceiling to wallboard gap is relatively small, a fire resistant and elastomeric caulk is commonly applied so as to fill any small gaps. In still another approach and as disclosed in U.S. Pat. Nos. 5,471,805 and 5,755,066 both to Becker, a slidable noncombustible secondary wall member is fastened to an especially configured steel header track and immediately adjacent to the wallboard. In this configuration, the secondary wall member provides a fire barrier that is able to accommodate ceiling deflections. All of these approaches, however, are relatively labor intensive and thus expensive.

Intumescent materials have long been used to seal certain types of construction gaps such as, for example, conduit through-holes. In this regard, intumescent and fire barrier materials (often referred to as firestop materials or fire retardant materials) have been used to reduce or eliminate the passage of smoke and fire through openings between walls and floors and the openings caused by through-penetrations (i.e., an opening in a floor or wall which passes all the way through from one room to another) in buildings, such as the voids left by burning or melting cable insulation caused by a fire in a modern office building. Characteristics of fire barrier materials suitable for typical commercial fire protection use include flexibility prior to exposure to heat, the ability to insulate and/or expand, and the ability to harden in place upon exposure to fire (i.e., to char sufficiently to deter the passage of heat, smoke, flames, and/or gases). Although many such materials are available, the industry has long sought better and more effective uses of these materials and novel approaches for better fire protection, especially in the context of dynamic head-of-wall construction joints and gaps.

Thus, and although construction joints and gaps are generally sealed in some manner (e.g., mineral wool and/or elastomeric coatings; see also, U.S. Patent Application No. 2006/0137293 to Klein), there are relatively few products and methods available that effectively and efficiently seal head-of-wall construction joints and gaps (to thereby significantly enhance the ability of such joints and gaps to withstand smoke and fire penetration). In particular, there are very few products and methods available that address the needs for adequate fire protection and sealing of dynamic head-of-wall systems associated with steel stud wall constructions. Thus, there is still a need in the art for new and improved fireblock systems and fire retarding devices, including related wall assemblies and methods. The present invention fulfills these needs and provides for further related advantages.

SUMMARY OF THE INVENTION

In brief, the present invention in one embodiment is directed to a fire retardant head-of-wall assembly configured to seal a linear head-of-wall construction joint or gap when exposed to a heat source. The innovative fire retardant head-of-wall assembly comprises: (1) an elongated sheet-metal footer track; (2) an elongated sheet-metal header track confronting and vertically spaced apart from the footer track, the header track including a web integrally connected to a pair of spaced apart and downwardly extending sidewalls, the web having a top exterior web surface positioned adjacent to a ceiling and a bottom interior web surface, each sidewall having inner and outer sidewall surfaces, each sidewall having an upper sidewall portion adjacent to the web and a lower sidewall portion; (3) an elongated intumescent strip affixed lengthwise on at least one of the outer sidewall surfaces of the pair of sidewalls, the intumescent strip being positioned on the upper sidewall portion, the intumescent strip having an outer strip surface offset from the outer sidewall surface an intumescent strip offset distance; (4) a plurality of sheet-metal studs having upper and lower end portions, the studs being vertically positioned between the spaced apart and confronting footer and header tracks such that the lower end portions are received into the footer track and the upper end portions are received into the header track, each of the upper end portions of the plurality of studs being spaced apart from the bottom interior web surface of the header track a first gap distance that allows for ceiling deflections; and (5) wallboard attached to at least one side of the plurality of studs, the wallboard having a top linear end surface positioned apart from the ceiling a second gap distance that allows for ceiling deflections and defines the construction joint of gap, the wallboard having an elongated upper interior wallboard surface in contact with the outer strip surface of the elongated intumescent strip.

In another embodiment, the present invention is directed to a fire retardant head-of-wall assembly, comprising: (1) an elongated sheet-metal footer track; (2) an elongated sheet-metal header track confronting and vertically spaced apart from the footer track, the header track including a web integrally connected to a pair of spaced apart and downwardly extending sidewalls, each sidewall having inner and outer sidewall surfaces, each sidewall having an upper sidewall portion adjacent to the web and a lower sidewall portion separated from the upper sidewall portion by an outwardly protruding curved bend that runs lengthwise along the sidewall; (3) an elongated intumescent strip affixed lengthwise on at least one of the outer sidewall surfaces of the pair of sidewalls, the intumescent strip being positioned on the upper sidewall portion; (4) a plurality of sheet-metal studs having upper and lower end portions, the studs being vertically positioned between the spaced apart and confronting footer and header tracks such that the lower end portions are received into the footer track and the upper end portions are received into the header track; and (5) wallboard attached to at least one side of the plurality of studs, the wallboard having an elongated upper interior wallboard surface in contact with or proximate to the outer strip surface of the elongated intumescent strip.

In another embodiment, the present invention is directed to an elongated U-shaped sheet-metal track that includes (1) a web integrally connected to a pair of spaced apart and outwardly extending sidewalls, (2) a plurality of vertically aligned slots positioned along at least one of the sidewalls, and (3) at least one intumescent strip positioned along the sidewall having the plurality of vertically aligned slots and juxtaposed to the web.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are intended to be illustrative and symbolic representations of certain exemplary embodiments of the present invention and as such they are not necessarily drawn to scale. In addition, it is to be expressly understood that the relative dimensions and distances depicted in the drawings (and described in the “Detailed Description of the Invention” section) are exemplary and may be varied in numerous ways without departing from the scope and essence of the present invention. Finally, like reference numerals have been used to designate like features throughout the several views of the drawings.

FIG. 1 illustrates a side perspective view of a fire retardant dynamic head-of-wall assembly in accordance with one embodiment of the present invention, wherein the head-of-wall assembly is configured to seal a linear head-of-wall construction joint or gap when exposed to a heat source such as a building fire.

FIG. 2A illustrates a side perspective view of a sheet-metal header track having intumescent strips positioned lengthwise along the sidewalls and above an outwardly facing protrusion in accordance with an embodiment of the present invention.

FIG. 2B illustrates a side perspective view of a sheet-metal header track having a single intumescent strip positioned lengthwise along one of the sidewalls in accordance with another embodiment of the present invention.

FIG. 2C illustrates a side perspective view of an L-shaped sheet-metal header track consisting of a top web connected to a single downwardly extending sidewall with a single intumescent strip positioned lengthwise along the sidewall in accordance with yet another embodiment of the present invention.

FIG. 3A illustrates a side view of an upper section of the fire retardant dynamic head-of-wall assembly shown in FIG. 1.

FIG. 3B illustrates a side view of an upper section of the fire retardant dynamic head-of-wall assembly shown in FIG. 1, but where the intumescent strips have been exposed to a heat source and, consequently, have expanded so as to seal the linear head-of-wall construction joint or gap.

FIG. 3C illustrates a side view of the upper section of the fire retardant dynamic head-of-wall assembly shown in FIG. 3A, but where the intumescent strip has been positioned such that it extends slightly above the top surface of the web, thereby causing the top edge of the intumescent strip to be in contact with the ceiling so as to provide for enhanced sound and smoke containment.

FIG. 4 illustrates a side perspective top partial view of the upper section of the fire retardant head-of-wall assembly shown in FIG. 1.

FIG. 5 illustrates a side perspective underneath partial view of the upper section of the fire retardant head-of-wall assembly shown in FIG. 1.

FIG. 6 illustrates an end view of the U-shaped sheet-metal track in accordance with an embodiment of the present invention, wherein a pair of curved bends protrude outwardly way from each sidewall a curved bend offset distance that is about the same as the thickness of the intumescent strip (and further shows an outer protective polymeric coating on the underlying intumescent material).

FIG. 7 illustrates an end view of the U-shaped sheet-metal track in accordance with an embodiment of the present invention, wherein a pair of outwardly facing elongated protrusions extend away from each sidewall a protrusion offset distance that is less than the thickness of the intumescent strip (and further shows an outer protective polymeric coating on the underlying intumescent material).

FIG. 8 illustrates an end view of the U-shaped sheet-metal track in accordance with an embodiment of the present invention, wherein a pair of outwardly facing elongated protrusions extend away from each sidewall a protrusion offset distance that is greater than the thickness of the intumescent strip (and further shows an outer protective polymeric coating on the underlying intumescent material).

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein like reference numerals designate identical or corresponding elements, and more particularly to FIGS. 1-8, the present invention in one embodiment is directed to a fire retardant head-of-wall assembly 10 configured to seal a linear head-of-wall construction joint or gap 12 when exposed to a heat source such as a building fire. As best shown in FIG. 1, the inventive fire retardant head-of-wall assembly 10 comprises an elongated sheet-metal footer track 14 confronting and vertically spaced apart from an elongated sheet-metal header track 16. The fire retardant head-of-wall assembly 10 further comprises a plurality of sheet-metal studs 18 having upper and lower end portions 20, 22 with the studs 18 being vertically positioned between the footer and header tracks 14, 16 such that the lower end portions 22 are received into the footer track 14 and the upper end portions 20 are received into the header track 16. More specifically, the lower end portions 22 of each stud 18 are engaged within the footer track 14 and adjacent to a top interior web surface 15 of the footer track 14, while the upper end portions 20 of each stud 18 are engaged within the header track 16 and proximate to a bottom interior web surface 23 of the header track 16.

In this configuration and as best shown in FIGS. 3A-C, each upper end portion 20 of the plurality of studs 18 is spaced apart from the bottom interior web surface 23 a first gap distance D₁ that allows for ceiling deflections (caused by seismic activity or moving overhead loads, for example). The first gap distance D₁ generally ranges from about ⅛ to about ⅝ inches (depending on the design specification of the wall assembly 10), and preferably is about ⅜ of an inch. In addition, wallboard 17 is attached to at least one side of the plurality of studs 18, with the wallboard 17 having a linear top end surface 19 positioned apart from a ceiling 33 a second gap distance D₂ that similarly allows for ceiling deflections and defines the aforementioned linear construction joint or gap 12. The second gap distance D₂ also generally ranges from about ⅛ to about ⅝ inches (depending on the design specification of the wall assembly 10), and preferably is also about ⅜ of an inch. In other words, the first gap distance D₁ and the second gap distance D₂ are preferably the same or about the same, thereby each allowing for ceiling deflections of the same amplitude.

As best shown in FIGS. 2A, 3A and 5, the elongated sheet-metal header track 16 (of the head-of-wall assembly 10) comprises a web 26 integrally connected to (and flanked by) a pair of spaced apart and downwardly extending sidewalls 28 (also sometimes referred to as legs or flanges). The web 26 includes the bottom interior web surface 23 and a top exterior web surface positioned adjacent to the ceiling 33 (in some embodiments, however, the head-of-wall assembly 10 may further comprise a compressible sheet material (not shown) such as, for example, a thin foamed plastic sheet, placed between the ceiling 33 and the top surface of the web 26 for purposes of enhanced sound and smoke containment, especially in cases where the ceiling surface is uneven or spawled). Each sidewall 28 is has inner and outer sidewall surfaces 29, 30. As shown, an elongated intumescent strip 34 is affixed lengthwise on at least one of the sidewalls 28, namely, on an upper portion of one of the outer sidewall surfaces 30 and above a lengthwise and centrally located (meaning in a central portion of the sidewall and not necessarily in the middle) and outwardly facing elongated protrusion 31, wherein the elongated protrusion 31 protrudes outwardly away from the outer sidewall surfaces 29, 30 a protrusion offset distance D₃. The intumescent strip 34 has an outer planar strip surface offset from the outer sidewall surface 30 an intumescent strip offset distance D₄ equal to its thickness (which is preferably about ⅛ inch). The intumescent strip offset distance D₄ is generally, but not necessarily, about the same or less than the protrusion offset distance D₃ thereby minimizing abrasive contact between the wallboard 17 and the outer planar intumescent strip surface. More specifically, and in some embodiments, the wallboard 17 has an elongated upper planar interior wallboard surface 21 that linearly contacts and bears against the outer apex surface of the curved bend 31, as well as (in some embodiments) the outer strip surface of the intumescent strip 34. Moreover, the intumescent strip 34 has a width W that is generally equal to at least twice the first gap distance D₁, while the top linear end surface 19 of the wallboard 17 is preferably positioned perpendicular and about midway along the width of the intumescent strip 34. In this configuration, the elongated intumescent strip 34 is able to slide up and down (i.e., cycle) with respect the stationary wallboard 34 when a ceiling 33 deflection event occurs. In some embodiments and as best seen in FIG. 3C, the intumescent strip 34 is positioned such that its top edge 25 extends slightly above the top surface of the web 26. In this configuration, the intumescent strip 34 contacts the ceiling 33 and provides for enhanced sound and smoke containment, especially in cases of an uneven or spawled ceiling surface.

The intumescent strip 34 is commercially available (e.g., 3M Company or The Rectorseal Corporation, U.S.A.) and preferably has an adhesive backing that allows it to be readily affixed onto the outer sidewall surface 30. Exemplary in this regard are the heat expandable compositions disclosed in U.S. Pat. No. 6,207,085 to Ackerman (incorporated herein by reference), which discloses a composition that, when subjected to heat, expands to form a heat-insulating barrier. A preferred composition contains expandable graphite (˜10-40 wt %), a fire retardant (˜10-40 wt %), and an optional inorganic intumescent filler (<50 wt %), all of which are admixed together with a resinous emulsion (˜30-60 wt %). The expandable graphite is generally manufactured by the oxidation of graphite flake in sulfuric acid (with such intercalated graphite being swellable or expandable up to about 100 times of its original volume when heated at high temperature). The fire retardant generally includes amine/phosphorous containing salts such as, for example, amine salts of phosphoric acid or lower alkyl esters thereof. A preferred fire retardant is a C₂-C₈ alkyl diamine phosphate. Intumescent activation or expansion generally begins at about 392° F. In order to ensure that the intumescent strip 34 stays in place when exposed to heat, it has been found that a commercially available (e.g., 3M Company, U.S.A.) fire-retardant epoxy adhesive may preferably also be used. In other words, a fire-retardant adhesive (not shown) may be interposed between the intumescent strip 34 and the outer sidewall surfaces 30 of the pair of sidewalls 28. In some embodiments, the intumescent strip 34 may on its top surface include a protective foil tape or polymeric coating 35 to protect the underlying intumescent material from degradation that may occur due to wall cycling.

In a preferred embodiment, the elongated sheet-metal header track 16 (of the head-of-wall assembly 10) also comprises a plurality of vertically aligned slots 36 positioned at regular intervals along the pair of downwardly extending sidewalls 28. Each slot 36 has a preferred slot length D₅ that is generally at least about two times greater than the first and second gap distances D₁, D₂, or preferably ranging from about ½ inch to about 6 inches (wherein each slot 36 may be partially covered by the intumescent strip 34). In this preferred embodiment, a plurality of fasteners 38 secure the upper end portions 20 of the plurality of studs 18 to the header track 16, with each fastener 38 extending through one of the slots 36 and preferably being positioned about midway along each respective slot length D₃ as shown in FIG. 5. In some embodiments, a lengthwise guideline 39 is printed or etched on each of the outer sidewall surfaces 29, 30 so as to intersect about the midway point of each slot 36. The purpose of the lengthwise guideline 39 is to assist the installer with proper fastener 38 placement. Each fastener 38 includes a fastener head that protrudes away from the outer sidewall surface 30 (of one of the sidewalls 28) a fastener head offset distance that is about the same or slightly less than the thickness of the intumescent strip 34 (thereby ensuring that the outer planar strip surface 35 of the intumescent strip 34 remains in intimate contact with the outer apex surface of the curved bend 31, as well as (in some embodiments) the elongated upper planar interior wallboard surface 21 so as to maintain a smoke and fire seal at all times, especially during a ceiling 33 deflection or cycling event)). In this configuration, the inventive fire retardant head-of-wall assembly 10 is able to readily accommodate ceiling deflections because the studs 18 and fasteners 38 are relatively unencumbered with respect to up and down ceiling 33 deflections (vertical movements over at least the first and second gap distances D₁, D₂ and half the slot lengths D₅). Moreover and when exposed to a heat source (not shown) such as a building fire, the intumescent strip 34 is able to expand so as to at least partially fill the construction joint or gap 12 as shown in FIG. 3B; and in so doing, retard or prevent the spread of smoke and fire. This expansion or intumescence of the intumescent strip 34 helps prevent noxious gases, flames, or other by-products that may be produced in a fire from penetrating into adjacent areas.

For purposes of illustration and not restriction, the following Example demonstrates various aspects and utility of the present invention.

EXAMPLE 1

Several mock-ups of a fire retardant head-of-wall assembly in accordance with the present invention were constructed and tested to evaluate the joint system's resistance to a heat source followed by a hose stream in accordance with Underwriters Laboratories, Inc.'s standards set forth in its Tests for Fire Resistance of Building Joint Systems—UL 2079. Each mock-up was constructed so as to have a ⅜ inch head-of-wall linear construction gap, and the construction gap was cycled over this distance (translating to a maximum of a ¾ inch gap when the ceiling was upwardly deflected a maximum distance of ⅜ inch, and to a minimum of no gap when the ceiling was downwardly deflected a maximum distance of ⅜ inch) in order to demonstrate that the head-of-wall assembly was able to withstand (meaning without failure of any of the wall assembly components) various levels of cycling. More specifically, the several mock-ups successfully passed cycling Levels I, II, and III (with Level I=1 cycle/min for 500 cycles (thermal expansion/contraction), Level II=10 cycles/min for 500 cycles (wind sway forces), and Level III=30 cycles/min (seismic forces)). After the successful cycling demonstration, the linear construction gap of one of the mock-ups was opened to its ¾ inch maximum and the whole mock-up was for a two hour period placed parallel and adjacent to an open oven heated to 1800° F. During this period no appreciable amounts of smoke or fire penetrated through the fire retardant head-of-wall assembly, and substantially all of the unexposed or far side wall materials (inclusive of the intumescent strip) remained intact and in place (meaning that the mock-up passed UL's “F-rating” for restricting fire passage). In addition, all of the unexposed or far side wall materials (inclusive of the intumescent strip) remained below 425° F. (meaning that the mock-up passed UL's “T-rating” for restricting thermal passage). Finally, and within about 5 minutes of being exposed to the open oven heat source, the exposed or near wall was subjected to a “hose stream” test (i.e., a 4 inch fire hose having a straight nozzle water stream at 30 psi for 30 seconds) and no direct water stream penetrated through the wall (meaning that the mock-up passed UL's “H-rating” for restricting hose stream passage). In view of the foregoing, the inventive fire retardant head-of-wall assembly has been certified as complaint with respect to Underwriters Laboratories, Inc.'s standards set forth in its Tests for Fire Resistance of Building Joint Systems—UL 2079.

While the present invention has been described in the context of the embodiments illustrated and described herein, the invention may be embodied in other specific ways or in other specific forms without departing from its spirit or essential characteristics. Therefore, the described embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing descriptions, and all changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. A fire retardant head-of-wall assembly configured to accommodate up and down ceiling deflections, comprising: an elongated sheet-metal footer track;an elongated sheet-metal header track confronting and vertically spaced apart from the footer track, the header track including a web integrally connected to a pair of spaced apart and downwardly extending sidewalls, at least one sidewall having an upper sidewall portion adjacent to the web and a lower sidewall portion separated from the upper sidewall portion by an outwardly facing protrusion that runs lengthwise along each sidewall; an elongated intumescent strip affixed lengthwise on at least one of the outer sidewall surfaces of the pair of sidewalls and above the outwardly facing protrusion;a plurality of sheet-metal studs having upper and lower end portions, the studs being vertically positioned between the spaced apart and confronting footer and header tracks such that the lower end portions are received into the footer track and the upper end portions are received into the header track; wallboard having an inner face and outer face attached to at least one side of the plurality of studs, the wallboard having an elongated upper interior wallboard surface in contact with or proximate to the outer strip surface of the elongated intumescent strip, the header track being movable relative to the plurality of studs and wallboard so as to be able to accommodate up and down ceiling deflections, and wherein the outwardly facing protrusion protects the intumescent material from compression associated with the wallboard by being substantially in contact with the inner face.

2. The fire retardant head-of-wall assembly of claim 1 wherein the elongated intumescent strip comprises expandable graphite and a fire retardant.

3. The fire retardant head-of-wall assembly of claim 2 wherein the fire retardant is a C2-C8 alkyl diamine phosphate.

4. The fire retardant head-of-wall assembly of claim 2, further comprising a plurality of fasteners securing the upper end portions of the plurality of studs to the header track, each fastener extending through one of the pair of sidewalls of the header track and the upper end portion of one of the plurality of studs.

5. The fire retardant head-of-wall assembly of claim 4 wherein the elongated sheet-metal header track includes a plurality of vertically aligned slots positioned along at least one of the pair of downwardly extending sidewalls, with each fastener extending through one of the plurality of slots.

6. The fire retardant head-of-wall assembly of claim 5 wherein the fasteners are positioned about in the middle of its respective vertically aligned slot.

7. The fire retardant head-of-wall assembly of claim 6 wherein the intumescent strip partially covers each of the plurality of vertically aligned slots.

8. The fire retardant head-of-wall assembly of claim 7 wherein a top linear end surface of the wallboard is positioned perpendicular and about midway along the width of the intumescent strip.

9. The fire retardant head-of-wall assembly of claim 2, further comprising an adhesive interposed between the intumescent strip and the at least one of the outer sidewall surfaces of the pair of sidewalls.

10. The fire retardant head-of-wall assembly of claim 2 wherein the intumescent strip has an outer protective polymeric coating.

11. The fire retardant head-of-wall assembly of claim 2 wherein the elongated sheet-metal header track has a generally U-shaped cross-section.

12. The fire retardant head-of-wall assembly of claim 2 wherein each of the plurality of sheet-metal studs has a C-shaped cross-section.

13. The fire retardant head-of-wall assembly of claim 1, further comprising a compressible material sheet positioned between the web and the ceiling.