Gypsum Area Separation Walls Provide Effective Fire Resistance and Sound Attenuation
Effective fire resistance and sound attenuation have long been important considerations in the design of multifamily dwellings, such as townhouses, condominiums, and apartments. Both objectives can be met inexpensively through the use of gypsum board area separation walls-sometimes referred to as fire walls, party walls, or townhouse separation walls.
Gypsum area separation walls are easy to erect and secure, and they meet all building code requirements. Fire resistive ratings easily reach two hours and more. And they can be erected up to four stories in height, depending on the manufacturer.
Complying with codes
Any area separation wall must meet certain basic requirements. It must be:
Continuous from the foundation to the underside of the protected roof sheathing or continue through the roof to form a parapet, and
Designed to allow for collapse of the construction on the side of the wall exposed to fire without collapse of the separation wall.
Every model building code recognizes the suitability of gypsum board area separation wall systems for resisting fire and attenuating sound. Though gypsum has inherent fire-resistive qualities, each model building code mandates that any wall system used for area separation must first be fire tested according to a specific test standard, such as ASTM E 119,"Standard Test Method for Fire Tests of Building Construction and Materials," or its equivalent.
Solid gypsum area separation walls
Gypsum board area separation wall systems come in two designs: solid systems and cavity-type systems. Cavity systems are constructed with components typically incorporated into either steel stud partition systems, or gypsum board shaft wall enclosures, such as those used to enclose an elevator shaft or duct shaft in a multi-story nonresidential building. Solid gypsum board type area separation walls systems incorporate three basic components:
One-inch thick type X gypsum board liner panels that are 2-feet wide and either 8-, 10-, 12- or 14-feet long.
Metal framing members, consisting of 2-inch-wide H-studs and U-shaped track.
"Break away" L-shape aluminum clips that soften at relatively low temperatures.
For two-hour fire resistance, the area separation wall consists of two layers of 1-inch thick liner panels. The panels slide into a horizontal track at the foundation or floor level and into the vertical studs that hold them in place. An inverted section of track caps the wall. To continue the wall higher, a track is fastened to the capping track of the lower wall. The stacking process repeats until an inverted track caps the completed final story or roof parapet.
L-shaped aluminum clips attach the gypsum board area separation wall to the adjacent wood frame structure. The clips attach to both sides of each H-stud at each floor or roof/ceiling intersection to provide lateral support for the area separation wall. The clips are designed to soften and break when exposed to high temperatures on the fire side.
During an intense fire, when one side of the wall system experiences temperatures of 1100 °F or higher, the clips will soften and break away. In this way, the adjacent structure on the fire side may collapse without pulling down the fire-resistive separation wall. The clips on the opposite side of the area separation wall remain intact, since temperatures on that side will be far below the point at which the clip will soften. As a result, the fire-resistive wall system will remain standing, sparing the adjacent living space from significant damage.
The clips must be manufactured from aluminum in a thickness and shape conforming to the requirements established by the representative fire test and the manufacturer of the area separation wall system. Otherwise the wall system may not function as intended.
In short, gypsum board area separation walls offer an excellent low-cost solution for separating townhouses, condos, and apartments. They are code compliant for both fire resistance and sound attenuation.
Michael
Gardner is Director of Promotion and Code Services for the Gypsum
Association, a trade organization that represents leading gypsum board
manufacturers in North America.
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