How to Apply Joint Compound to Sheetrock

Fill a drywall mud trough with compound. Scoop compound onto the blade of an 8- to 10-inch wide drywall finishing knife, also known as a drywall trowel. Fill the valley created by the tapered edges along the two sheets of drywall where they meet, starting at the top of the wall. Press the compound into the seam and drag the knife over the top of it, with the blade perpendicular to the seam, to smooth it.

Continue adding and smoothing compound until you reach the the bottom of the seam. Fill the seam in the same way, working side to side for horizontal seams. Roll out enough paper drywall joint tape to cover the length of the seam and cut it off with a utility knife.

Start at the top, or one end of your seam and press the tape into the wet compound with the folded edge in the center of the tape facing down. Drag the drywall knife over the tape to smooth it with the blade perpendicular to the seam and leaning slightly in the direction of the stroke.

Add a small amount of compound on top of the tape with the knife, smoothing it as you go. Watch for ripples in the paper tape. Have a helper hold the top end, or one end if working a horizontal seam, firmly against the wall, and smooth the entire piece back into place if needed to release wrinkles.

Allow the compound to dry until it all has a white chalky appearance. Add a third thin coat, called the top, or topping coat, of compound over the taped area, using the wide knife to blend the edges into the panels on either side. Keep the goal in mind of raising this area just slightly so that it can be sanded down to perfectly meet the panels on either side.

Allow the compound to dry thoroughly. Sand the seam smooth with a drywall sanding screen on an extension pole. Use a fine grit screen for best results.