How to Apply Joint Compound to Smooth Out Walls

Joint compound is a type of plaster that's used to finish off the seams between sheets of drywall during construction.

Apply Joint Compound to Smooth Out WallsApply Joint Compound to Smooth Out Walls
Applied correctly, it renders the seams between individual sheets invisible once painted. Joints must be covered in drywall tape in order to give the joint compound something to adhere to so that the compound can be applied smoothly.

Run your hand along the surface to feel for raised screw heads left sticking out from the wall during construction. Sink any protruding screw heads with a screw gun so that the heads are flush with the surface of the wall.

Press drywall tape over each seam between sheets of drywall, ripping off any excess tape at the top and bottom of each seam.

Spread joint compound over the seams, using a drywall knife to completely cover the tape. Make the line of joint compound 4 inches wide, or 2 inches wide on either side of the seam, and completely flat. Spread a dab of joint compound flat over each screw hole as well.

Wait at least six hours, or overnight, for the joint compound to dry. Run the long edge of the drywall knife over the dried compound to knock off any lumps.

Spread a second coat of joint compound on top of the first in a seam 6 inches wide, so it completely covers the first seam. Let the compound dry for at least six hours. Scrape the area with your drywall knife again to remove any additional lumps.

Spread on a third and final coat of joint compound in a seam 8 inches wide -- an inch wider on either side of the seam than the previous application. Let it dry at least six hours or overnight.

Sand the seams very lightly with a sanding pad to make them flat and even. Use a broom to brush dust off the wall's surface.

Things You Will Need

  • Screw gun
  • Drywall tape (mesh style)
  • Pre-mixed joint compound
  • Wide drywall knife
  • Drywall sanding pad

Tip

  • Paper drywall tape is available, but is more complicated to use than mesh-style tape, which has adhesive on it. Paper tape needs a base of joint compound to adhere to, adding an additional step to this process.

Warning

  • Wear a particle mask when sanding.