Conventional plaster application changed radically in the 1960s and 1970s. Veneer plaster systems were developed at that time. Drywall was being substituted for plaster at that time as well.
The Big Sheets
Drywall offered a different approach to quickly achieve a finished wall surface. The 4' x 8' and 4' x 12' panels of drywall could be rapidly applied to framing members. A standard sized room could be ready for finishing in an hour or two.
During the 1950s, conventional plaster systems required the installation of "gypsum lath." These were smaller (16" x 48") pieces of material which looked, at first blush, like typical drywall. However, these smaller pieces of gypsum plaster lath actually were covered with a special paper which absorbed the water in a special manner so as not to harm the inner gypsum core. The paper was also manufactured in such a way as to provide an excellent surface for the plaster to grab on to. The traditional two coat plaster system (brown coat/white coat) was applied over this gypsum plaster lath system. However, it was quite labor intensive to nail on these smaller pieces of gypsum lath. It made sense to switch to larger pieces of gypsum lath and develop a one coat plaster system.
Veneer Plaster Systems
Although drywall was rapidly becoming popular, drywall did not have the overall performance characteristics of conventional plaster. Plaster surfaces offered better joint concealment, fewer nail pops, a hard monolithic surface which could be easily decorated, and plaster was more quickly finished than drywall.
Also, the joint compounds used to finish drywall, even after they dried, could be easily dissolved by water. Water applied to the surface of a traditional plaster wall for short lengths of time did not harm the plaster in any way. Veneer plaster systems changed this. They took the best qualities of the two systems and combined them.
Veneer plaster systems use a gypsum core panel as the base for the plaster coat. This panel has a gypsum core very similar to drywall. However, the paper used to cover the gypsum core is different from regular drywall. It is a special multi-ply paper. The top ply has the capability to readily absorb water and provide a good bonding surface for the plaster coat. The bottom ply, however, is water resistant. This ply protects the inner gypsum core from being softened by the water in the wet plaster. Some manufacturers use a special blue paper on this gypsum panel. Plasterers often refer to it as "blue board." Special plasters were developed which allowed a one step finishing process. This plaster is applied in a thin coat directly over the gypsum panel. The plaster thickness usually ranges between 1/16th to 3/32nd of an inch. Conventional plasters were often 1/2 inch thick.
Advantages of Veneer Plaster
Veneer plaster finishes offer two distinct advantages over drywall - dust and money. Dust is kept to a minimum with these products. The veneer plaster is applied in a wet state and troweled to a smooth surface. No sanding is required.
A one step veneer plaster can cut up to 75 percent off of a similar drywall finishing production time. After the gypsum wall panels are hung, a one coat veneer system requires one step. A similar drywall job requires four finishing processes. The last step of a drywall job, as many people know, involves the creation of massive quantities of dust.
Certain plasters offer tremendous durability. Some achieve compressive strengths of up to 3,000 pounds per square inch. This strength rivals that of some concrete mixtures! Drywall can not make similar claims.
Plaster wall systems offer greater decorating flexibility as well. Wall coverings can be applied to plaster as easily as they can be applied to drywall. However, plaster systems allow you to readily remove the wall coverings in the future without damaging the wall surface. The paper covering of drywall is often damaged, or partially removed when wall coverings are stripped from drywall.
Veneer plaster is affordable. Often it costs just 25 percent more than a drywall finish. While this may seem like a large differential, it is, in fact, not. This upgrade may only add one-half of one percent to the overall cost of a construction project. When you consider the long term durability that veneer plaster systems offer, it is a tremendous value.