Drywall Joint Compound

Drywall joint compound is used, along with drywall joint tape, to fill the seams between drywall panels. It is also used to cover fastener heads and patch damage to drywall panels in order to create a smooth, uniform surface on walls and ceilings. There are two primary types of joint compound: setting type and drying type. Setting type (hot mud) is typically supplied as a powder and mixed with water on site. It is a reactive plaster which limits the application time but decreases the time between coats. Drying type compound is most usually supplied in "ready-mix" form, where it is already combined with water and must only be mixed prior to application. This ready-mix, drying type of joint compound appears to be the most commonly used so is the type presented in this CP. Drying type joint compounds contain a small percentage of a polymeric binder, typically a polyvinyl acetate, ethylene vinyl acetate, or acrylic vinyl acetate polymer (or some combination). As a result, these joint compounds may be called "vinyl base ready mix" or "vinyl-type mixture" or "vinyl type". This is in reference to the binder type and is not referring to PVC (which is also commonly referred to as vinyl). There are many variations in the ready-mix category: all-purpose standard weight, light-weight, mid-weight, taping compound, topping compound, etc. Lightweight compounds contain some lighter weight fillers such as glass microspheres or expanded perlite. "Reduced dust" or "low dust" formulations may include additional content such as a wax or oil and a surfactant. There are also some ready-mix setting type compounds that contain calcium sulfate hemihydrate (gypsum) or plaster instead of limestone. These formulations require the addition of a retarder and an accelerator. This CP is focused on an all-purpose standard weight drying type compound. Some information on functional additives used in other types of compounds in captured in the All Contents tab.

Historically, some joint compound has contained intentionally-added asbestos. The Consumer Product Safety Commission banned intentional inclusion of asbestos in these materials starting in 1978. Because talc deposits can be co-located with asbestos deposits, and joint compounds commonly contain talc, it is possible that some joint compound contains asbestos contamination from the talc. HBN has not seen any specific evidence of this. At least one manufacturer that uses talc reports that they have documentation from their suppliers indicating no detectable asbestos, and many joint compound manufacturers advertise their products as being "asbestos-free."

Crystalline silica is a common contaminant in joint compound. This is an occupational concern because the joint compound is sanded after it dries, and respirable silica in the dust that forms during the sanding process is considered a carcinogen. Crystalline silica is difficult to avoid in standard joint compound, but some products report lower levels than others. In 2017, OSHA placed new rules on crystalline silica exposure during construction work generally. Dust levels in the air during drywall finishing can be decreased by using vacuum dust collection or wet-sanding methods.

A historical version of this Common Product is available here: https://pharos.habitablefuture.org/common-products/2204474.