Wall finishes are mostly decorative; however, most wall finishes do add rigidity to the structure. Drywall prevents wood frame walls from racking, for example. Finishes also conceal and support insulation and air/vapor barriers. Electrical and mechanical systems are also concealed behind wall finishes. In this blog post we will discuss three of the most popular wall finishes.
Plaster and Drywall:
Plaster and drywall (modern prefabricated plaster) are very popular wall finishes- with good reason! Plaster and drywall are durable, chemically inert, inexpensive, easy to repair easy to paint/ wallpaper, fire resistant, rodent and insect resistant, and good at blocking sound. How could you not like a material with all these qualities?!? Prior to 1900, plaster was made with lime, which is calcium oxide, or from crushed limestone, which is calcium carbonate. This material was heated to very high temperatures to create quicklime. Water added to quicklime generates a chemical reaction that results in slaked (or hydrated lime), which is good for plaster. The plaster was mixed with water on-site to generate the finished product. In the past 100 years, gypsum has been used to make plaster. Gypsum is calcium sulfate. The gypsum is crushed and calcined. It becomes plaster of Paris at this point. Additives are put into the plaster of Paris to create plaster and water is added on-site to create the finished product.
Gypsum lath was an interim step between plaster and drywall. These prefabricated plaster boards were covered with paper on both sides. This lath replaced wood and wire lath. Two- or three coat plaster was then added to the gypsum lath. Although drywall was invented much earlier, it became popular in the 1950’s. It is also commonly called Sheetrock, which is actually just a brand name. Drywall is also called wallboard, plasterboard, gypboard, and gypsumboard. None of these are brand names. Drywall is plaster manufactured in a factory and covered on both sides with treated paper. Drywall is more stable than plaster and is smoother than most field-applied plaster systems. However, it is thinner and weaker than conventional plaster. The joints are taped, and in poor work, the joints are visible. Typically, the sides of the drywall sheets are tapered to allow the joint compound and reinforcing paper or mesh to fill the recess and provide a flush surface. The paper drywall tape used in finishing joints performs better than the mesh according to most. Drywall needs a more uniform, perfectly level substrate than plaster. Drywall is not as flexible as plaster. It’s harder to do curved walls successfully with drywall, and again, joints can be a problem.
There is another hybrid between plaster and drywall known as veneer plaster. This approach is not widely used. Some people refer to this as a skim coat plaster. It is typically a 1/8-inch plaster finish coat applied over a special wallboard.
Wood paneling has largely been replaced with plywood and hardboard paneling, which are considerably less expensive and easier to apply. Plywood and hardboard paneling can be very thin. This paneling should be at least ¼-inch thick to be applied directly to wall studs on 16-inch centers. Where the paneling is thinner, 3/8-inch drywall, for example, is typically used behind the paneling. Drywall would similarly be used behind even 1/4-inch paneling where studs are spaced more than 16 inches apart.
There are other common finishes, such as tile, brick, stucco and concrete. Typically these finishes are used for accenting rather than the entire wall, but there are always exceptions.