Recently, at a conference, I heard the term plaster bandied about in forms that were confusing. The difference in the use of the words stucco, plaster, and mortar is based more on use than composition. In the industry it is most common to use the word plaster when referring to interior work, stucco when referring to exterior work and mortar when referring to the stuff that goes between bricks and stones.
This post is about plaster, or, in other words, the stuff on the interior of a building.
The two most common choices for wall interiors in a new home is either plaster or drywall. There is also Veneer plaster, and we will be talking about that too.
Many people don’t know they still have a choice or that there is a difference between these three types. We at RFJ would like to let you know that you do have a choice and we hope that this information will help you make the appropriate choice for your situation.
Let us start with plaster. The most common type of plaster used on interior walls in gypsum plaster. This is most commonly done through a three-coat process.
In plaster a lath system first must be secured to the framing of your walls. Historically, lath was made from wood strips, but in modern times you will most likely find metal. This lath gives the plaster something to grab onto.
Metal Lath ready for the first coat of Plaster
After the lath has been installed the plaster goes on. The plaster usually comes in 50-pound bags and is in a dry powder form. This is mixed with water to produce the proper consistency. While this sounds simple, it actually takes years of practice to get a proper workable consistency.
Once the plaster is ready it is applied to the lath. The first coat (called the scratch coat) is applied, and the scratched with a scarifier or scratcher and left to dry.
Scarifier and Scraper Trowel
The second coat, or brown coat, is then applied. This coat is applied using the same techniques as the scratch coat, however, instead of using a scratcher, an instrument called a darby or a trowel is used. The darby or trowel is used to ensure that the brown coat is even and uniform.
Finally the third coat is applied. This is applied with a hawk and trowel, depending on the finish you desire. The finish can be customized in different ways.
A Hawk and Trowel
The advantage of a plaster wall is the thickness; since a plaster wall is thicker than drywall you have improved sound baffling, less likelihood of warping and increased fireproofing. A plaster wall also works best for irregular and rounded surfaces.
Now lets take a look at Drywall. Drywall is also called wallboard, plasterboard, Sheetrock, or just plain “rock”, but we will use the term Drywall. Drywall is made by squeezing gypsum and water between two different layers of paper and then heating. On one side of the paper is the face, which is strong and smooth, the other side, or back, is rougher in texture.
Stacks of various types of Drywall waiting for installation on a job
Installing the drywall is quick and easy. The boards are cut to fit and then secured directly to the framing with screws. Next the joints are taped with either a paper or fiberglass-mesh tape at the joints, corners, and places where the boards have been fastened to the walls in order to cover the screws.
Then, typically, three coats of joint compound are added. Joint compound comes ready mixed in plastic tubs.
The wall is sanded after each coat of joint compound to give it a smoother surface. Once the third layer has dried it is ready for paint.
There are obvious advantages to drywall. First, and most important to many is the process takes less time and manpower, and is therefore considerably less expensive. However, drywall can be damaged easily. Also drywall is susceptible to water damage, thus increasing potential for mold. There are new products on the market to help prevent these mold problems.
Veneer plaster is a cross between the two. Veneer plaster starts with the gypsum board base. This gypsum board, called blue board, has special moisture and adhesive qualities. After the board is installed either one or two coats of plaster are applied very similarly to the way we discussed above in regular plaster.
There is an old world charm to plaster walls, but there is also versatility and less cost involved in drywall. At RFJ we proudly do all three types of plaster finishes, and knowing that we have nearly 70 years of experience, you can rest assured that no matter which process you choose, we will give you the highest quality service and product available.