How to Sand Drywall Mud

Planning to sand drywall must be done carefully. It is one of the worst jobs in home renovating. The dust is so fine that it gets into everything and is difficult to remove, or even to vacuum. In fact, vacuuming drywall dust can even void the warranty on many vacuums. Sanding is the last chance to get everything right, but it can only be done well if you have taken care with all the other processes, like taping and mudding. If your sanding is not done well, it will show when the paint is dry. 

Step 1 - Preparation of the Room

The dust is as fine as flour and will sneak into every small crevice, even throughout the house if you are not careful. Make sure you close any cabinets and lay drop cloths on the floor. Use masking tape to seal off any air conditioning or heating ducts. If you have screens on your windows or doors, remove them so you won’t have to clean them later. Make sure you wear a good mask or respirator as well as goggles and comfortable clothing. 

Step 2 - Sanding the Drywall Joint Compound

Run your hand down all the seams to find any that have hollows, fill them and let the compound dry. Most of the work will involve using a hand sander on low levels. Use a pole sander on ceilings and places you cannot reach. These tools are available at home centers and hardware stores. Set up a lamp so it shines across the seams and shows up any flaws in the tape. Doing it right now will pay off later.

Use a courser grade of sandpaper for grinding down the high spots and a 150 grit drywall sandpaper for the rest. You will need to frequently change the sheets for a good finish. It will take three or four sheets of sandpaper to finish an average sized bedroom. Use a push-pull motion and an even pressure to work the sander. Don’t use much pressure and move it in a circular motion if you need to smooth out any shallow scratches. With pole sanders, use a sweeping or push-pull motion, twisting the handle to control the sanding head. This will allow the heat to switch directions and turn around the inside corners. You need to avoid scuffing the paper tape, it is easy to wear through. The seam edges should look smooth after sanding. 

Step 3 - Finishing the Fiddly Bits and Corners

Use handheld sandpaper on a block to finish the inside corners and around fittings, such as outlets and lamps, because an electrical sander can cause damage here by slamming into adjacent walls. Another option is to use a damp sanding sponge to work on those areas. 

Step 4 - Finishing Up

It is now advised that you don’t sweep up all the dust before painting. Leave an even coat of dust on the surface, and it will bind with the paint, filling in any scratches and pin holes. Prime the wall and paint. Let it dry completely, then clean up any dust.