Drywall – A Possible Source of Asbestos Contamination
Modern drywall does not use asbestos, but drywall workers – also called drywall tapers and removers – are one of the risk groups for asbestos exposure. Buildings in the past were often constructed with asbestos insulation or asbestos embedded into other construction materials. Both installation and removal of drywall raises the risk of stirring up asbestos-containing dust.
Today, drywall is a building material that is synonymous with the building process itself. Homes, offices, factories, schools, all are built with large amounts of the material known as drywall. Drywall is used around the world in the construction of walls and ceilings. While many variations of drywall exist, all drywall is basically gypsum plaster hardened between two pieces of paper liner and cut into sheets. It is also sometimes called sheetrock.
Drywall was first produced by the United States Gypsum Company in 1916. Although it was called “wallboard” at the time, it was basically the same gypsum and paper sandwich we use today. Despite being showcased during the 1934 World’s Fair, wallboard failed to catch on until World War II. Before then, plaster was used to cover framed walls. Laying plaster took time and manpower: the usual procedure for finishing a wall before drywall consisted of using three layers of plaster that had to be applied carefully and smoothly and allowed to dry. Drywall, a product that required far less labor and time to cut and hang, got its breakthrough during World War II when laborers were in short supply. After drywall became common, plaster disappeared almost immediately. Any house made after 1940 in the U.S is almost guaranteed to contain drywall.
Gypsum is the primary ingredient in drywall, and is a somewhat liquid form of calcium sulfate. The raw gypsum is calcined, then mixed with a fiber, usually paper or fiberglass, as well as a variety of other chemicals that produce the desired consistency and characteristics the manufacturer is looking for. (In decades past, asbestos was often mixed into the drywall.) That mixture is then poured between two pieces of paper or fiberglass mats. The mixture sets in a large drying chamber until it hardens. The drywall is then cut into sheets in an assembly line process. In the U.S and Canada, drywall sheets typically come in four foot wide sheets, with varying lengths. With the rising popularity of nine foot high ceilings (as opposed to standard eight foot), drywall is now being manufactured in 4.5 foot wide sheets as well. The most common drywall thickness is half an inch (.5 in) but drywall thickness ranges from a quarter inch to an inch thick.
There are many kinds of drywall available, but the major differences between products have to do with where the drywall will be hung. Specifically, drywalling areas around a fire hazard or areas that might receive more moisture than a usual room (like a bathroom or kitchen) require special kinds of drywall. Fire resistant drywall is usually thicker than standard drywall and has fire resistant compounds added to the gypsum mixture. Water resistant drywall is usually made with green paper, and is accordingly called “green board.” Green board comes with an oil-based additive in the paper layer that keeps water from rotting the gypsum. There are also soundproof drywall products available, as well as more eco-friendly drywall made from recycled building materials.
An experienced two man drywalling team can drywall a whole house in a day or two. To hang drywall, the wall must be properly prepped, meaning that any old nails or protrusions are removed from the studs, which are ideally sixteen inches apart. The drywall sheets are then cut to match the dimensions of the space where it will be hung, usually with a utility knife and a yardstick. The pieces of drywall are hung with nails or screws, although screws designed for use with drywall work best. A good guideline for the amount of screws or nails needed is one pound of nails/screws for every four by eight foot piece of drywall. Every protruding angle of drywall will require a drywall corner, a very light metal right angle that holds drywall at the angle necessary for constructing a precise wall angle. After hanging the drywall, the wall must be plastered over. Plaster is used to smooth over seems and nails or screws. This can come in a mix or in a premixed form. An experienced drywaller needs about five gallons of plaster for every 1000 square feet of drywall. Drywall tape can also be very helpful in providing a smooth, flat surface to put over seems and gaps in preparation for plastering.
Reducing the Risk of Asbestos Exposure
Any sort of poking around in buildings can be dangerous, expecially if asbestos was used in construction. Face masks can dramatically reduce the risk of inhalantion of asbestos dust. Although any general contractor can install drywall, it is a relatively easy process and can be done by any amateur who possesses a few essential tools and is willing to invest some time. Because of this many homeowners do their own drywall work. Everyone, both professionals and amateurs, should wear masks when exposed to construction debris dust, especially if the debris is suspected to contain asbestos.