All Things Gypsum: Repair of Fire-Rated Gypsum Board Systems
Small holes, such as those caused by a door knob, can be repaired by patching. To maintain the integrity of the surface membrane, the gypsum board patch must be mechanically secured in the layer or layers of board that have been damaged; attachment with joint compound only is not acceptable. The patching material should be cut from type X or proprietary-type X gypsum board of a thickness and type equal to that of the original materials.
To repair the hole, cut a square or rectangular patch that is slightly larger than the damaged area from a piece of gypsum board. Then, using the patch as a template, enlarge the damaged surface to match exactly the size of the patching piece. Use caution when cutting into the stud cavity to avoid electrical shock or creating water leaks. Remove and replace any damaged insulation or other material that is in the cavity.
Suitable attachment surfaceTo provide a suitable attachment surface for the patch, install metal-runner track around all four sides of the damaged area (note that the existing studs may be used on one or more sides of the patch if the damaged area has been cut back to a stud). Using fasteners spaced no more than 8 inches on center, secure the patching material to the exposed face of the runner tracks or studs. Fasteners should be the same length and have the same head diameter and shank diameter as those prescribed in the original fire test system.
Several proprietary clip products are available which provide mechanical support for patching small holes. Manufacturers of these products should be contacted for information.
If the mechanically or environmentally damaged area covers more than 100 square inches in 100 square feet of gypsum surface area, all materials in the damaged area must be removed back to the original framing to make the repair. Framing in the area to be repaired must be inspected and replaced, if necessary. Maximum framing spacing requirements of the original fire-rated system description must be strictly followed; additional framing members should be added as needed to facilitate the repair.
Once the framing is repaired, replacement gypsum board panels or pieces should be installed in the opening. The gypsum board must be fastened to the framing using fastener spacing not greater than that required by the original fire-rated system description. Ends and edges of the gypsum board that are not backed by framing materials should be supported with metal runner track.
Multiple-layered systemsMultiple-layer systems typically require that joints be staggered between layers. Proper repair of multiple-layer systems may require that face layers of board be removed beyond the base layer joint so as to retain the staggered joint feature.
To restore the system's fire-resistive integrity, a patched or repaired area generally must be treated with joint-treatment material. At a minimum, the edges of the patched area must be treated with joint tape and joint compound in a manner consistent with the requirements for joint treatment application established by the original fire-rated system description or applicable building code. For example, systems derived from GA-600, "Gypsum Association Fire Resistance Design Manual" are required to have the joints in all face layers taped (minimum Level 1 as specified in GA-214, "Levels of Gypsum Board Finish") and fastener heads treated. Systems derived from other sources may have different requirements.
The appearance of the repair should also be evaluated with particular emphasis given to damaged areas that are visible to building or facility occupants. A poorly installed patch on a wall in a hotel ballroom, for example, could affect the appearance of the entire wall and might detract from the overall aesthetic quality of the facility.
Finishing the damaged wall or ceiling area using a Level 5 finish as described in GA-214, "Levels of Gypsum Board Finish" is one method for addressing appearance concerns that arise from a patched surface. The Level 5 finish should be applied to the entire repaired area, so that the total planar wall or ceiling area between two break points has been resurfaced. Treatment of only the immediate area around the repair should be avoided as it may cause the repair to become more obvious.
To improve the appearance of large, repaired areas that are structurally sound, but aesthetically unacceptable, a new layer of gypsum board may be attached to the existing, repaired surface with adhesive or fasteners. Assuming that the partition or ceiling has been correctly repaired, the new layer of gypsum board may be of any thickness or core type and can be added without adversely affecting the fire resistance rating or acoustical performance of the repaired system.
Gypsum board in fire-rated systems that has been exposed to elevated levels of moisture for an extended period should be assessed for potential damage. In general, board that has been exposed to water should be replaced unless all of the following conditions are met:
The source of the water or moisture is identified and eliminated.
The water or moisture to which the gypsum board was exposed was not contaminated. (Gypsum board that has been exposed to sewage or flood waters must be replaced.)
The gypsum board can be dried thoroughly before mold growth begins (typically 24 to 48 hour depending on environmental conditions).
The gypsum board is structurally sound and there is no evidence of rusting fasteners or physical damage that would diminish the physical properties of the gypsum board or system.
If there is ever a doubt about whether to keep or replace gypsum board that has been exposed to moisture, replace it.
Repair of a water- or moisture-damaged system is accomplished using the procedure described above. Specific attention should be given to a thorough inspection of framing members to ensure they also have not been adversely impacted by water damage.
Repair of a fire-rated wall or ceiling must be accomplished with care, as retaining the integrity of the system must be one of the paramount principles of the repair plan. However, when planned and accomplished correctly, fire-rated gypsum board systems can be repaired reasonably quickly and with minimal disruption to building occupants. It is the ease of repair that, among other positive attributes, makes gypsum board an appealing choice for fire-rated systems.