How to Sand Drywall and Drywall Mud Successfully

Hanging the drywall is often the easiest part of a drywall project. Learning how to tape and mud drywall, how to sand drywall and drywall mud is often far more challenging. Doing the mudding job well takes plenty of skill and practice. Even if you master this part of the job, though, you can ruin it pretty quickly with a haphazard sanding job, forcing you to start over. You have multiple options for learning how to sand drywall, and we’ll help you figure out which one will work best for you.

What is Sanding Drywall?

After hanging the drywall, you’ll use drywall tape to cover the seams located between the sheets you hung. You will then use drywall mud to cover the tape and any embedded screw heads.

The mud, also called joint compound, dries in place and hides these imperfections. Applying the mud in a perfectly flat line is almost impossible, even for a seasoned drywall pro. This is where learning how to sand drywall mud enters the picture. By sanding, you remove slightly uneven spots and bumps in the mud, creating a flat wall that’s ready for paint.

One clarification: When people talk about sanding drywall, they’re really talking about sanding the drywall mud, not the paper covering on the sheet of drywall itself. 

How Much Does it Cost to Sand Drywall?

It can be tough to determine the exact cost of having a pro sand your drywall, because most pros incorporate sanding into the overall cost of installing drywall. 

Having a pro finish the drywall—which usually includes taping, mudding, sanding, and priming—usually costs between $0.70 and $1.30 per square foot. This is about two to three times as much as the cost to hang drywall alone. 

If your contractor discusses the work in terms of drywall finish levels, sanding involves level four or level five. Some contractors refer to level five as skim coating. The cost to skim coat walls usually ranges between $1.10 and $1.30 per square foot.

For sanding alone, expect to pay $0.30 to $0.50 per square foot if this is the only job you want the pro to do for you. However, it’s difficult to find a pro to just do sanding. At the very least, most of them prefer to both mud and sand.

How to Prep for Sanding Drywall

The first step to sanding drywall properly is to wait for the mud to completely dry. Sanding wet mud typically results in gouging and ends up ruining the mudding job, forcing you to start over. How long does drywall mud take to dry? Expect to wait about 24 hours to allow everything to dry properly.

After it dries, you should put on protective clothing before sanding, including safety goggles and a mask. Place a drop cloth on the floor to catch dust and to help with cleanup. 

You may want to hang plastic sheeting over entrances to the room and close any vents in the room to limit dust moving through the air into other areas of the house. Drape furniture with plastic sheeting to protect it.

How to Sand Drywall and Drywall Mud

You have multiple techniques you can use when working on how to sand drywall mud. You may want to use more than one technique, as each one has some specific instances where it provides the best results.

Drywall Sponge

Also called wet sanding, using a dampened drywall sponge re-wets the mud and gently smooths out gouges and ridges. It works a bit like using a wet sponge to smooth out grout between floor tiles. 

Learning how to wet sand drywall can greatly reduce dust in the air. Using sandpaper, on the other hand, creates quite a bit of fine dust that seems to stick to everything. 

To wet sand the drywall, soak the drywall sponge in water. (Do not use a kitchen sponge, as it will be too abrasive.) After wringing it out, gently rub the sponge in a circular motion until you end up with a relatively flat surface in the drywall mud. 

Let everything dry to see if any imperfections remain. Repeat the process if necessary. Because wet sanding often doesn’t create a perfectly flat finish, you may still need to use fine-grit sandpaper for some finishing touches.

The sponge is the best tool to use in corners, as sandpaper likely will cause gouges unless you use extreme care.

Sandpaper by Hand

Use a fine-grit sandpaper to flatten areas that have too much mud or where the mud has gouges. If the mud is rough, 100- or 120-grit sandpaper is usable. However, 150-grit sandpaper is better. If you are doing touchup work after wet sanding or doing fine sanding, 220-grit sandpaper is the best option. 

You can place the sandpaper on a pole sander or on a sanding block to help you do the work. Use a very light touch across screw holes and across seam tape when sanding by hand.

Using sandpaper gives you the smoothest finish. However, it will create a lot of dust.

Electric Sander

Using an electric sander on drywall mud is incredibly challenging, and it’s really only useful on large drywall projects by people with plenty of experience.

Most novices are going to use too much force with the electric sander, removing too much mud, damaging the drywall tape, or damaging the drywall itself. Use a very light touch and move the sander in an overlapping, back-and-forth pattern for the best results. 

Never stop the sander while it’s in contact with the drywall or the mud. This causes gouges and noticeable swirl patterns. 

One advantage to an electric sander versus sanding by hand is that it may have a vacuum attachment that limits the amount of stray dust generated.

Tips for Avoiding Problems With Sanding Drywall

You may encounter some issues when attempting to sand drywall, such as:

• Gouges: If you sand with too much force, you can gouge the mud, leaving it uneven.

• Exposed tape: Removing too much mud through sanding may expose the drywall tape.

• Low light: You may need to bring in additional lighting to be able to see any uneven spots in the mud, especially if working in new construction or remodeling areas where you don’t have electrical power.

• Wet mud: If you try to sand mud that’s still wet, you will create a huge mess. Wait for it to dry.

• Damaged paper: Drywall sheets have a paper covering that protects the drywall. What is drywall made of? It consists primarily of crushed gypsum with various additives. Sanding too hard could tear the paper and expose the gypsum, causing significant longevity issues.

• Not sanding after priming: After you sand and prime the drywall, the paint may reveal areas with slight imperfections. After everything dries, you can sand again and then re-prime these individual areas.

• Sloppily applied mud: Taking your time when applying each coat of drywall mud can save you time on sanding. If the mud is pretty smooth when it dries, you won’t need to sand as much as if you sloppily applied the mud.

DIY vs. Hiring a Pro

By learning how to install drywall and sand drywall mud yourself, you are going to save quite a bit of money. Labor for drywall professionals can cost up to $100 per hour. 

However, because sanding is such a challenging job to do well, it is going to take a novice significantly longer to do the job than a pro. If you make a mistake and sand too hard, you’ll have to start over with mudding and taping. In the long run, it may be cheaper and less frustrating to hire a local drywall contractor to do the work right the first time.

There’s nothing wrong with learning how to sand drywall yourself to save some money, though. Just understand that it takes a lot of practice and patience. At the very least, reach out to a local drywall installer for a cost estimate, so you can weigh whether doing the job yourself is worth it.