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December 2014   

Wavy Wall Work

By: Lee G. Jones

Q: Our condo association hired a contractor to install drywall in several places. The work has started, and there are places where the gaps between the panels are approaching 3/4-inch. The walls also seem to be excessively wavy. The condo association complained that this appears to be inferior work, but the contractor claims he can fill the gaps afterward and everything will be fine. We are skeptical that this work meets industry standards but don’t have the needed information to challenge the contractor. Is there some reference standard the association can refer to that defines acceptable drywall work?

A: The International Building Code cites two standards for the application of gypsum wallboard, GA-216, Application and Finishing of Gypsum Panel Products, and ASTM C840, Standard Specification for Application and Finishing of Gypsum Board. Both standards offer language regarding the gaps and straightness acceptable in gypsum board surfaces.

ASTM C840 says in essence that there must be "moderate contact” between panels, without spelling out what constitutes moderate contact. GA-216 is a bit more specific and offers the following regarding gaps:

"4.6.7 Gypsum panel products shall be abutted so as to be in contact with one another but not forced together.

"4.6.8 Where gaps occur at gypsum panel product joints, they shall be not greater than 1/4 in. (6 mm) and shall be prefilled with joint compound as specified in Sections and

" Gaps not greater than 1/8 in. (3 mm) shall be prefilled with either drying-type or setting-type joint compound.

" Gaps greater than 1/8 in. (3 mm) shall be prefilled with setting-type joint compound.

Regarding the straightness of gypsum board surfaces, GA-216 offers the following (the language in C840 is almost identical) in section 4.1.8: "The attachment surface of any framing or furring member shall not vary more than 1/8 in. (3 mm) from the plane of the faces of adjacent framing or furring members.”

So, if construction in your condominium must comply with the IBC, it sounds like the contractor hired by your association had some redo work to perform.

And because this work is being done in a condominium, one other consideration comes to mind. One or more of these assemblies may in fact need to meet some fire-resistance and sound-containment ratings. Walls and ceilings between condo units are generally required in the building codes to protect neighbors from fire, smoke and sound that may originate in a neighboring unit. So, if such an assembly is necessary, the following information found in GA-600, Fire Resistance Design Manual, would also apply: "Fire-resistance ratings, STCs, FSTCs, and IICs are the results of tests conducted on systems composed of specific materials put together in a specified manner. Substitution of other materials or deviation from the specified construction could adversely affect performance.”

In layman’s terms, this passage means that a gypsum board assembly that is built to meet a fire-resistance and/or sound-containment rating must be built exactly as the tested design describes. Any rated assembly will be constructed following the constraints laid out in GA-216 and C840 mentioned above and will also be free of any gaps through which fire, smoke and sound could travel into the next unit.

Q: We are about to begin a job that includes applying an intumescent material on some exposed steel surfaces. The weather is now starting to get cold. What are the limitations for exposure when applying this material?

A: A few lines out of AWCI’s recently updated "Technical Manual 12-B, Standard Practice for the Testing and Inspection of Field Applied Thin-Film Intumescent Fire-Resistive Materials; an Annotated Guide” cover this topic nicely. Section 3.3 on temperature says, "A minimum substrate temperature of 50°F (10°C) shall be maintained during and for a minimum of 72 hours after the application of the TFIFRM, unless otherwise recommended by the TFIFRM manufacturer.” And section 4 on site conditions says this about temperature: "A minimum temperature of 50°F (10°C) shall be maintained during the application and drying/curing periods required for the TFIFRM except as otherwise recommended by the TFIFRM manufacturer. If heating equipment is required, the TFIFRM manufacturer shall be consulted for specific recommendations.” In that same section, there is this information on humidity: "Relative humidity in the work area shall not exceed 75 percent during the application and drying/curing period required for the TFIFRM except as otherwise recommended by the TFIFRM manufacturer.”

Also, most of the materials involve a primer and a top coat that also must be applied under similar favorable conditions.

Lee G. Jones is AWCI’s director of technical services. Send your questions to, or call him directly at (703) 538.1611.

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