What is Drywall?
Drywall is a type of panel (sometimes called a board) made from gypsum and paper. It is used to cover interior framing members during construction to create a solid smooth surface that forms walls and ceilings. Drywall can be installed over wood or metal studs or even over cinder block if drywall adhesive is used.
What is Dry Wall?
Dry wall is a common misspelling of the word drywall. However, considering the history of drywall, it makes sense that some people mistakenly pronounce it as two words, dry and wall. To understand why we have to understand how walls were made before drywall was invented.
How Were Walls Made Before Drywall was Invented?
Before drywall was invented, it was common to use plaster on interior walls and ceilings. In areas where plaster was not used, wood paneling or shiplap was also common.
Plaster is installed by spreading several layers of wet gypsum slurry across a lath substrate made of either wood or metal mesh. Wet plaster is trowelled smooth on the wall and finished with a very thin layer of finishing plaster. Topcoat finishing plaster is white in color and creates a very hard smooth finish.
Plaster comes in a powdered form similar to cement. It is mixed with water on the job site using large mixers. If you are familiar with the way stucco is applied, you can imagine a similar process for installing plaster since these trades share some common techniques. Once the plaster has dried, a thin layer of hardened gypsum material covers the surface of the interior wall.
Because plaster is applied wet, the concept of creating interior walls was closely tied to the need for water. Building interior walls was intrinsically a “wet wall” process. If you wanted gypsum interior walls instead of wood paneling or Shiplap, you had to make a wall out of plaster, a wet material, and let it dry.
Drywall on the other hand comes in large panels of dried gypsum that has been pre-formed in a factory into thin layers of solid gypsum. Drywall panels are installed using a hammer and nails using techniques more closely related to installing wood paneling or Shiplap. The only water needed is for taping and finishing drywall joints. We may not think applying dry plaster panels is anything special. However, drywall panels were quite a new concept for those who relied on plaster for interior gypsum walls.
For someone accustomed to making interior walls using an elaborate process of mixing plaster and troweling it on like stucco while it was still wet, the idea that you could have a similar finished product without the hassle of wet plaster was quite a revelation. With this background, it is easy to understand why people naturally called it drywall. The name drywall emphasizes the benefits of a dry-wall process.
The skills needed to install drywall are very similar to carpentry skills used for rough-in framing. In fact, installing drywall panels is similar to installing wood paneling or shiplap.
Drywall revolutionized the way interior walls were constructed due to it's ease of installation. Recognizing how much of a simplification it was to be able to use pre-formed dry gypsum panels instead of the longtime standard of wet plaster explains how the term drywall gained popularity.
How is Drywall Made?
Gypsum is the primary ingredient in drywall. Gypsum is a soft white mineral that is commonly found in association with sedimentary rock. Gypsum is crushed into a powder and heated to about 120 - 180°C (248 - 356°F). The high temperature changes the chemical structure of gypsum into what is known as plaster powder.
Water (and other ingredients depending on the type of drywall) is added to make gypsum slurry. Fiberglass is sometimes added to the slurry to increase its fire-resistant properties. Gypsum slurry is poured to form a panel of even thickness and width. Drywall is commonly made in ½-inch and ⅝-inch thicknesses, and 48-inch or 54-inch widths. The slurry is then wrapped with thick paper before it dries.
Once the gypsum slurry dries, it hardens to form a solid gypsum panel sandwiched between two layers of drywall paper. This panel is cut into varying lengths, stacked, and sent to distribution centers. Drywall panels are commonly available in 8 ft, 10 ft, and 12 ft lengths.
How to cut drywall
Drywall is easy to cut using a utility knife or keyhole saw. The paper that wraps around a sheet of drywall adds strength and stability to the gypsum within. Gypsum on its own does not have very much interlaminar strength. So when you cut the paper on both sides of a sheet of drywall it becomes very easy to break apart the gypsum within. This concept of cutting, or scoring, drywall paper and then snapping the gypsum within is the basic concept of cutting drywall panels.
If you want to cut a sheet of drywall in half, all you need to do is use a utility knife to score a line through the paper on the front of the sheet from top to bottom. Once the paper is cut, you can then easily snap the drywall along the score line.
You don't have to cut very deeply through the inner gypsum material. Cutting through the paper alone will allow you to bend the sheet in half and it should fold easily. Then, you can simply score the drywall paper on the backside of the sheet of drywall where you have just snapped it in half and the two pieces will separate easily.
If you want to make circular cuts or arching cuts, you will need to use a different technique. For those types of cuts, you can use either a drywall keyhole saw or a drywall router. Drywall routers can be used with blades that are made specifically for cutting drywall. You don't want to use a wood blade on a traditional router for cutting drywall.
In Summary
In many respects, drywall is similar to plaster in that both are used to form interior walls and ceilings and both are comprised of the same basic material. The primary difference between drywall and plaster is that with drywall, gypsum slurry is formed into pre-poured panels before installation, whereas plaster is spread directly in place.
