How to Apply Sheetrock Mud for Drywall Joints

Sheetrock mud, also commonly referred to as “joint compound", offers a wealth of uses. One of the most prevalent ways in which it is used is to finish out drywall joints. Once you learn how to do this, it's a simple job that can make a big difference in how well the final finish turns out on your walls.

All you need in the way of tools and materials (after the drywall has been hung) is the sheetrock mud/joint compound (sold in large buckets, ready to mix and apply), a utility or joint knife (or scissors), drywall joint tape, and sandpaper.

The First Step

To make a smooth connection between sheets of drywall so that you can paint or wallpaper a wall, you first need to apply sheetrock mud in a very thin layer along the seam. This first layer should only be about 1/8 inch thick and will act as an adhesive for the joint tape, which you will apply next. Alternatively, you can use tape that already has adhesive on it and skip this first step, but most pros go with the tape that requires adhesion by using joint compound.

As you smooth on your first layer of tape after you apply sheetrock mud, assuming you've used the non-adhesive type, press firmly down on the tape with your joint knife. Ideally, you want to see at least a small amount of sheetrock mud coming out from both sides of the tape as you go over it with your knife. This ensures that you have forced out any air bubbles that might be lurking within the compound. Air bubbles in sheetrock mud may sound like a small detail, but if you leave them in, they can ruin the smooth-looking finish you want to wind up with.

After you apply sheetrock mud and the joint tape, and have thoroughly smoothed it out, allow it to dry for at least overnight, preferably for 24 hours. Once it has dried completely, go over it with sandpaper to give it the smoothest surface possible. If there are any bits of tape sticking out, snip these off with a pair of scissors or a sharp utility knife.

The Second Application

Once this first layer of mud and tape has been sanded down smooth, apply sheetrock mud again, spreading it in another thin layer about six inches wide over the taped joint. Using your joint knife, feather the outside edges as much as possible. Again, allow it dry completely and sand once more. It is now ready for paint primer or wallpaper.

Knowing how to apply sheetrock mud can also help when you want to fill in knotholes or depressions in wood that is to be painted. It can also be used to repair holes in walls or to replace missing plaster. Sheetrock mud or joint compound doesn't cost all that much, and it's a great thing to have around. It's a versatile material, so learning how to use it can be a valuable part of your do-it-yourself knowledge bank.