Posted by Nirav Ashara in What is the difference between drywall and plaster? on Sunday, June 7, 2009
What is the difference between drywall and plaster?
When building a home or remodeling, people usually think about the granite countertops, the extensive square footage or the number of windows in the new space. Much of the time, little thought is given to one of the most integral parts of the home -- the interior walls.
Most people don't think about the walls in their homes unless there's a problem or they move into a studio apartment. Yet, interior walls provide privacy and separation. They can also act as sound barriers, insulators and even offer additional fire resistance.
Two of the most common forms of interior wall materials are plaster and drywall. Plaster has been used since ancient times. The earliest plaster was usually made of lime, sand, animal hair and water. Egyptian tombs, such as that of Queen Nefertari, feature paintings on the plaster walls that line their interiors. Ancient Roman homes are known to have been decorated with fresco artwork. Frescos are works of art that are created with different pigments on wet plaster.
An alternative to lime-based plasters, gypsum-based plasters had a faster drying time . This new form of plaster grew in popularity because it could speed up the building process.
As technology advanced, drywall became more durable and readily available. By the 1950s, drywall had surged in popularity as an interior wall material. The product now covers a majority of the interior walls in modern day homes.
In this article, we'll explore the composition, advantages and disadvantages of plaster and drywall for interior wall applications.
Inside Plaster
The most common form of plaster for interior walls is gypsum plaster. Plaster walls are generally created through a three-coat process. To begin, lath must be secured to the framing. Historically, lath has been made of wood strips, but more recently metal or plasterboard have come into use. The lath gives the gooey plaster something to hold onto.
After the lath is in place, the plaster compound must be mixed. The compound usually comes dry and must be mixed with water. While this step may sound fairly easy, a certain amount of skill and experience is needed to get the right consistency [source: Nash]. Then, the plaster can finally be applied to the wall. The first coat of plaster is applied, scratched and left to dry. It is followed by the second coat, or brown coat, and then the wall is finished off with a final layer.
Due to the number of coats and lathing, a plaster wall tends to be thicker than a drywall wall, which can create a greater air barrier [source: Heberle and Scutella]. This thickness also creates a good sound barrier between rooms. If the lathing and framing are done well, plaster can provide a much more rigid wall leading to reduced likelihood of buckling or breaking. Since plaster is not a solid when it's applied to the wall, it can be a good choice for curved or irregular surfaces. Finally, the gypsum within the plaster has a high water content, which gives the walls fire-resistant qualities.
Even with these benefits, plaster has fallen out of favor with homeowners today. Let's look at some possibilities for why that might have happened. First, the plastering process is labor intensive, causing the price to rise. Plastering is also time-consuming -- in applying and drying time. In addition, while plaster is very durable, it can crack with the settling of the building or improper installation. Some of these cracks can be fixed with plaster or a setting-type compound, yet others require structural restoration.
These may be some of the reasons that homeowners and remodelers are now more likely to opt for the drywall. Let's take a closer look at this interior wall material.
Inside Drywall
For basic gypsum drywall, the calcined gypsum is mixed with water and occasionally additives to create the core material. The viscous material is then squeezed, or flattened, between two different layers of paper and dried. One side of the paper is the face, which is strong and smooth, while the other side, or back, has a rougher texture.
Installing drywall is a fairly quick process compared to that of plastering. The boards are cut to fit the shape of the walls. They're then secured to the rough framing of the house. After the boards are in place, corner bead is attached to the corners to give them a straight edge. The walls are then taped with either paper or fiberglass-mesh tape at the joints, corners and places where the boards have been fastened to the wall. Then, the typical three layers of joint compound are added. After each layer, the wall is sanded to give a smoother surface. Once the third layer had dried, the wall is ready to be painted.
There are obvious advantages to drywall over plaster. First, the process of installation requires less time and labor, which can translate to less cost. Drywall also helps to reduce noise along with having fire-resistant properties due to the water in the boards.
While drywall does have many advantages as an interior wall material, it's not invincible. Drywall can be damaged by the settling of the building or homeowner accidents. A common problem is nail or screw pops, when the head of these fasteners creates a bulge or becomes visible through the drywall.
Secondly, gypsum drywall is susceptible to water damage if exposed to elevated levels of moisture over long periods of time. There are specialty drywall boards with additives that are designed for better water-resistance.
Along with water sensitivity, gypsum drywall boards can have mold problems. To decrease the chance for mold, new gypsum drywall boards are going paperless.
Whether you choose the versatility of drywall or the old-world charm of plaster walls, interior walls shape the look, flow and feel of your home. Knowing about the advantages and disadvantages of both plaster and drywall help you to choose the best system for your lifestyle.
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