FIELD OF THE INVENTION

[0001] The disclosed embodiments relate to a fire-resistant wall assembly and a method for constructing a fire-resistant wall assembly. In particular, the disclosed embodiments relate to a fire-resistant wall assembly and a method of constructing same formed of sheets of fire-rated gypsum wallboard with sheets of cement fiberboard fastened on an outer surface thereof.

BACKGROUND OF THE INVENTION

[0002] Gypsum board, commonly known as drywall, is the technical product name used by manufacturers for a specific board with a gypsum core and a paper facing. Gypsum board is the building material typically used for wall, ceiling, and partition systems in residential, institutional, and commercial structures and is designed to provide a monolithic surface when joints and fastener heads are covered with a joint treatment system.

[0003] One principal advantage of gypsum board over plywood, hardboard, and fiberboard is its strong fire resistance. Gypsum products also provide sound absorption, economy, versatility, quality, and convenience.

SUMMARY OF THE INVENTION

[0004] According to one aspect of the invention, a method for constructing a fire- resistant wall assembly includes attaching sheets of fire-rated gypsum board to a framework having metal studs using fasteners, each of the sheets of gypsum board being fastened to two of the studs with at least one intermediate stud therebetween. The method further includes applying heat-resistant double-sided tape to seams between adjacent ones of the sheets of gypsum board. The method further includes attaching with fasteners sheets of cement fiberboard, each of the sheets of cement fiberboard being fastened to two of the studs with at least one intermediate stud therebetween so that seams between adjacent ones of the sheets of cement fiberboard are horizontally displaced with respect to the seams between adjacent ones of the sheets of gypsum board.

[0005] According to one aspect of the invention, the cement fiberboard fasteners are at least about 10% smaller than a predrilled hole into which the cement fiberboard fasteners are inserted. The cement fiberboard fasteners are tightened to a torque which is at least about 10% less than a maximum torque of the cement fiberboard fasteners.

[0006] According to one aspect of the invention, a fire-resistant wall assembly includes sheets of fire-rated gypsum board attached with fasteners to a framework having metal studs, each of the sheets of gypsum board being fastened to two of the studs with at least one intermediate stud therebetween. The wall assembly further includes heat- resistant double-sided tape overlying seams between adjacent ones of the sheets of gypsum board. The wall assembly further includes sheets of cement fiberboard attached with fasteners, each of the sheets of cement fiberboard being fastened to two of the studs with at least one intermediate stud therebetween so that seams between adjacent ones of the sheets of cement fiberboard are horizontally displaced with respect to the seams between adjacent ones of the sheets of gypsum board. The cement fiberboard fasteners are at least about 10% smaller than a predrilled hole into which the cement fiberboard fasteners are inserted. The cement fiberboard fasteners are tightened to a torque which is at least about 10% less than a maximum torque of the cement fiberboard fasteners.

[0007] The disclosed embodiments may include one or more of the following features:

The sheets of cement fiberboard may have a thickness of about 1 /8 inch (4 mm).

The cement fiberboard fasteners may be at least about 25% smaller than a predrilled hole into which the cement fiberboard fasteners are inserted.

The cement fiberboard fasteners may be at least about 35% smaller than a predrilled hole into which the cement fiberboard fasteners are inserted.

The cement fiberboard fasteners may be between about 10% and about 25% smaller than a predrilled hole into which the cement fiberboard fasteners are inserted.

The cement fiberboard fasteners may be between about 10% and about 35% smaller than a predrilled hole into which the cement fiberboard fasteners are inserted.

A width of the gypsum board sheets may be about 4 feet and a width of the cement fiberboard sheets may be about 4 feet.

The cement fiberboard fasteners may be tightened to a torque at least about 25% less than a maximum torque of the cement fiberboard fasteners.

The cement fiberboard fasteners may be tightened to a torque between about 10% and about 25% less than a maximum torque of the cement fiberboard fasteners.

The cement fiberboard fasteners may be tightened to a torque between about 10% and about 35% less than a maximum torque of the cement fiberboard fasteners.

[0008] An original size of the pre-drilled holes in the cement fiberboard may be about 3/16 inch (5.0 mm), and these holes may be drilled through to increase their diameter to about ¼ inch (6.0 mm), in which case a fastener having a diameter of .189 inch (4.8 mm) may be used and all of the aforementioned dimensions may vary +/- 10%, or in particular embodiments by +/- 25%, depending upon the particular materials used.

[0009] As discussed above, the disclosed embodiments provide a fire-resistant wall assembly and a method of constructing same formed of sheets of fire-rated gypsum wallboard and sheets of cement fiberboard on an outer surface thereof. The cement fiberboard fasteners are placed in a particular configuration to improve fire resistance. Specifically, the fasteners have a diameter which is less than a diameter of the predrilled holes in the cement fiberboard into which they are inserted. Also, the fasteners are not fully tightened. This configuration helps prevent damage to the cement fiberboard as the heat from a fire causes the fasteners to expand. This, in turn, improves the fire resistance of the wall assembly.

[0010] The use of double-sided fire-resistant tape on the seams between the gypsum board sheets improves the fire resistance provided by the gypsum board, as it helps prevent the spread of fire through the seams. The use of double-sided tape also obviates the need for fasteners in the central portion of the cement fiberboard, as it prevents undesirable movement and/or vibration of the cement fiberboard when the wall assembly is installed in a structure, such as, for example the interior walls of a building.

[0011 ] The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the drawings:

[0013] Figure 1 A is an exploded view of a cross section of a wall;

[0014] Figure 1 B is a view of a cross section of a wall;

[0015] Figure 1 C is a view of a wall;

[0016] Figure 2 is a framework;

[0017] Figure 3 is the wall with gypsum board installed;

[0018] Figure 4 is the wall with insulation installed;

[0019] Figure 5 is a completed wall;

[0020] Figure 6A is an unexposed wall surface at fire endurance test completion;

[0021] Figure 6B is the exposed surface at fire endurance test completion;

[0022] Figure 7 shows thermocouple locations on the wall during test;

[0023] Figure 8 is a graph of furnace temperature with respect to time;

[0024] Figure 9 is a graph of the temperatures measured by the thermocouples during test;

[0025] Figure 10A shows the unexposed surface after a hose test completion; and

[0026] Figure 10B shows the exposed surface after a hose test completion.

DETAILED DESCRIPTION

[0027] Although example embodiments have been shown and described in this specification and figures, it would be appreciated by those skilled in the art that changes may be made to the illustrated and/or described example embodiments without departing from their principles and spirit. [0028] Figures 1 A, 1 B, and 1 C depict a fire-resistant wall assembly 10 according to one aspect of the invention. Figure 1 A is an exploded view of a cross section of a wall. Figure 1 B is a view of a cross section of a wall, and Figure 1 C is a typical wall elevation of the fire-resistant wall 10. The wall is typically a non-load bearing wall.

[0029] Fire-resistant wall assembly 10 includes sheets of gypsum board 16, which are preferably fire rated, attached with fasteners 20 to a framework 25 having metal studs 14. The fasteners 20 are arranges approximately every 18-24 inches. Each of the sheets of gypsum board is fastened to two of the studs with at least one intermediate stud therebetween. The fire-resistant wall assembly 10 further includes heat-resistant double- sided tape 17 overlying seams between adjacent ones of the sheets of gypsum board. The fire-resistant wall assembly 10 further includes sheets of cement fiberboard 18 attached with fasteners to the metal studs 14 of the framework 25. Each of the sheets of cement fiberboard is fastened to two of the metal studs 14 with at least one intermediate stud therebetween so that seams between adjacent ones of the sheets of cement fiberboard are horizontally displaced with respect to the seams between adjacent ones of the sheets of gypsum board. Preferably, the seams are displaced half a width of the gypsum board 16. The gypsum boards and cement sheets are typically sold in 4 foot x 8 foot sheets. For example, if the gypsum board is four (4) feet wide, the cement fiberboard sheets are horizontally offset two (2) feet. As one skilled in the art will appreciate, the gypsum boards and cement fiberboards will be trimmed to appropriate lengths for a given wall.

[0030] The cement fiberboard fasteners are at least about 10% smaller than a predrilled hole into which the cement fiberboard fasteners are inserted. The cement fiberboard fasteners are tightened to a torque which is at least about 10% less than a maximum torque of the cement fiberboard fasteners.

[0031] As shown, an interior sheathing 16 comprises a single layer of Gypsum board, preferably a 5/8 inch thick National Gypsum Gold Bond® XP® Fire-Shield® Gypsum Board meeting ASTM C 1396 that is fastened to the steel framing 14 with #6 x 1 -1 /4 inch long flat head self-drilling fasteners spaced 8 inches on center around the perimeter. One inch wide double-faced tape Type VHB™ manufactured by 3M was added to the gypsum joints prior to the exterior (unexposed) cladding install. The unexposed surface is the surface that is not exposed to heating during test. An interior cladding 18, preferably a 1 /8 inch (4 mm) thick cement fiber board is fastened over the mounted gypsum board 16 so to not intersect the gypsum board joints. In one embodiment, the cement fiber board 18 is fastened with 0.1890 inch x 1 .5 inch (4.8 mm x 38 mm) aluminum, granite-colored fasteners. These fasteners were installed via 1 /4 inch predrilled holes every 19-3/4 inch on the perimeter of every piece of the cement fiber board 18. To prevent damage to the cement fiber board 18, the fasteners should not be overtightened as the cement fiber board 18 is attached to the core wall.

[0032] The steel framing comprises framing members 14. The framing members 14, shown in Figure 2, are preferably 3-5/8 inch 25 gauge steel studs with a 2-1 /2 inch flange. The studs or framing members 14 are arranged at 24 inch centers and fastened to a steel track 26, shown in Figure 2, with #6 x 1 /2 inch long self-drilling fasteners.

[0033] In one embodiment, the wall assembly includes cavity insulation 15. Preferably, the insulation is 3-1 /2 inch thick R-15 mineral fiber insulation that is friction fit inside the stud cavities. Alternatively, the insulation can be a foam insulation, or the like. [0034] An exterior sheathing 16 comprises Gypsum board, preferably a single layer of 5/8 inch thick National Gypsum Gold Bond® XP® Fire-Shield® Gypsum Board meeting ASTM C 1396 that is fastened to the steel framing 14 with #6 x 1 -1/4 inch long flat head self-drilling fasteners spaced 8 inches on center around the perimeter. One inch wide double-faced tape Type VHB™ manufactured by 3M was added to the gypsum joints prior to the exterior (unexposed) cladding install. An interior cladding 18, preferably a 1 /8 inch (4 mm) thick cement fiber board is fastened over the mounted gypsum board 16 so to not intersect the gypsum board joints. In one embodiment, the cement fiber board 18 is fastened with 0.1890 inch x 1 .5 inch (4.8 mm x 38 mm) aluminum, granite-colored fasteners. These fasteners were installed via 1 /4 inch predrilled holes every 19-3/4 inch on the perimeter of every piece of the cement fiber board 18. To prevent damage to the cement fiber board 18, the fasteners should not be overtightened as the cement fiber board 18 is attached to the core wall.

[0035] Figures 2-5 depict a wall during construction. Figure 2 depicts the steel framing and steel track 26. Figure 3 depicts the wall with gypsum board 16 installed. It should be noted that the fire-resistant wall 10 has a similar appearance once the cement board 18 is installed. A partial cut-away is included to show the studs 14 and track 26. Figure 4 shows the framing 14 and the insulation 15. Also visible in Figure 4 is the masonry 30 to which the track 26 is affixed. Figure 5 is the completed wall assembly with the cement fiber board installed. It should be noted that the seams between the sheathing layers do not coincide with one another. In a preferred embodiment, the seams are offset by half a width of the materials used. For example, for a four (4) foot section of sheathing, the next layer will be offset by two (2) feet so that the seams do not overlap. It should be noted that both sides of the frame need not be covered with a gypsum layer 16 and a cement board layer 18. At least one side of the frame comprises a gypsum layer 16 and a cement board layer 18 and the other side can be either or both a gypsum layer 16 and a cement board layer 18.

[0036] The wall assembly was subjected to fire resistance testing. The purpose of fire resistance testing is to measure a building element's ability to resist the transfer of energy and hot gases through the element and subjecting adjacent rooms, structures, etc. from a single standardized fire scenario. The test measures performance by quantifying a temperature rise on an unexposed face of the wall assembly when the exposed side is subjected to the ASTM E1 19 Time vs. Temperature curve. The exposed surface is the surface that is exposed to heating during test. It addition to exposing the wall assembly to the fire test, the standard provides procedures to test the wall assembly's ability to resist the cooling effects of a water hose stream test. After the fire test, the specimen is subjected to the hose stream test outlined in ASTM E2226. If the end-use of the element is intended for structural support, it must also maintain its integrity by holding

[0037] A furnace is used to perform the fire resistance testing. The furnace used for testing has an exposure space of 14ft wide by 1 2ft. tall by 4 ft. deep. The furnace is equipped with six burners, each capable of producing 1 .5 MBtu/hr of energy. Three burners are positioned on each side wall of the furnace to allow for an even distribution of heat flux across the surface area of the test specimen. The exposed area of the furnace is reduced to 10ft. by 10 ft. by utilizing a frame consisting of steel and concrete with the exposed surface protected by fiber ceramic blankets. The temperature inside the furnace is controlled by adjusting a blower speed of air provided to the burners. This temperature is determined by the average of the nine thermocouples symmetrically placed behind the assembly. The locations of the thermocouples are shown in Figure 6A. The Neutral- pressure-plane is controlled by two pressure transducers that adjust the opening of the damper.

[0038] To perform fire resistance testing a fire-resistant wall assembly 10 is built inside a 10 ft. by 10 ft. steel frame test fixture with the inside perimeter lined with solid concrete blocks, and positioned against the open face of the furnace. Ten 24 gauge, Type K thermocouples 1 1 covered by 6 in. by 6 in. by 0.4 in. thick dry felt pads 35 and positioned on the unexposed surfaces of the fire-resistant wall assembly 10 to measure heat transmission as shown in Figures 6A and 7. The fire-resistant wall assembly 10 was subjected to a fire exposure test under non-loadbearing conditions and then subjected to the ASTM E2226 hose stream test under non-loadbearing ng conditions. The fire exposure test the ASTM E1 19 Time vs. Temperature curve shown in Figure 8. The data for the Time vs. Temperature curve is presented in Table 1 .

[0039] The testing comprises a 60 minute fire exposure test followed by a 30 psi water pressure hose stream applied for 60 seconds to the exposed surfaces per the requirements of ASTME2226. Two tests of the wall assembly were conducted. The results appear in tables 3 and 4. Figure 9 is a graph showing the temperatures measured by the thermocouples 1 1 during the fire exposure test. Table 5 shows the temperatures measured by the thermocouples 1 1 during the test that were used to create the graph of Figure 9.

1 0:00 lCement fiber board on exposed surface falls off the wall into the |

55:34 jCrack appears on the unexposed surface on the two foot section j jof cement j

60:00 iFire endurance test concluded no significant visual observations, j

Hose Stream 1 1

|Hose stream did penetrate through the unexposed surface during j

[0040] The test reveals that fire-resistant wall assembly 10 met the conditions of acceptance of ASTM E1 19 when exposed to a fire resistance rating of 60 minutes. Figure 10A is the unexposed surface after a hose test completion and Figure 10B is the exposed surface after a hose test completion.

[0041] Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the present invention, disclosure, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

[0042] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.