Panel Size and Layout
The standard rule is to install the largest drywall panels you can safely handle. Drywall panels are 4 feet wide and come in standard lengths up to 16-foot long. If your wall is 8 feet high and 16 feet long, you could install four, 4-foot by 8-foot panels, horizontally, with two on top and two on bottom, or you could install just two 16-foot panels horizontally. By using large panels on every wall, you’ll substantially reduce the amount of joint compound you need.
Drywall mud must be applied in multiple thin coats, because the mud shrinks as it dries. Scoop up about 1/2 cup of fresh mud at a time. Any more, and you could end up with excess that you have to scrape and sand. Any less, and you may not be working quickly enough to fill and smooth the seams before the compound starts to dry.
Drywall contractors butt panels tightly together to reduce taping. The initial application of compound will require a little more compound if the seams gap. The real need for more mud, however, comes later, because the large amount of mud filling the seams dries slowly, which creates depressions that require more than two additional coats of mud to smooth out.
Square Foot Estimating
Despite the variables that determine how much mud you’ll need per panel, if you’re estimating materials for a project, plan on using approximately 1 gallon of premixed mud per 100 square feet of wall space. Don’t subtract windows and doors when figuring wall space. For a 12-foot-by-12-foot room, you’ll need approximately 6 gallons of joint compound. This amount allows you to apply the mud three times, which is the standard for most residential drywall applications.