The simple reason why more DIYers don't install and finish drywall more often is easy to understand—the dust. Even the most careful taping and mudding job requires that the joints be sanded with a sanding screen or sandpaper, and that action invariably creates dust that flies everywhere and gets into everything. It travels into the farthest regions of your home, deep into your clothes and hair. Even wearing good eye protection and a particle mask doesn't fully prevent the awful powder from entering your eyes and lungs.
Drywall dust is so incredibly fine and invasive that the warranties of some house vacuums are considered void if you use them to remove drywall dust. But there is one method that can reduce your dust output to nearly zero: wet-sanding.
What Is Wet-Sanding?
Wet-sanding is the process of using a damp sponge to smooth out and remove excess taping compound after it dries. When moistened with a sponge, drywall compound begins to dissolve and loosen, and it can then be smoothed out. Wet-sanding is normally done with a very thick, stiff sponge. There are special sponges designed specifically for this task, or you can use any large, stiff household sponge—preferably an artificial sponge rather than a natural sponge, which tends to be too soft.
However, this process is far from perfect, and it's hardly a panacea for all drywall woes. Some pros view wet-sanding more as "joint smudging" than actual sanding, since so much of the taping compound remains on the wall rather than on your sponge. But there can be real value to smudging out the edges of the joints because it makes the seams less visible or even invisible after painting.
Wet sponging drywall compound is a slower process than dry sanding. If you're interested in speed, you'll want to dry-sand. Nor does wet-sanding produce a perfectly smooth surface. Because you are using a sponge―which is flexible―your finished wall may exhibit gentle waves. And if you wipe down the walls too vigorously with a sponge that is too wet, you can dissolve and remove too much of the taping compound, which will require that you go back and apply more mud. But all of these drawbacks may well be worth the single important benefit—a joint-smoothing operation that is completely without dust.
Equipment / Tools
- Drywall sponge
Produces no dust
Better at smoothing roughness
Requires just a bucket and sponge
Makes walls wet; requires drying time before priming
Not practical for large areas
Does not create a mirror-smooth finish
Takes longer than dry-sanding
Wet the Sponge
Fill a bucket with warm water. Dip the sponge into the water then wring it out. Drywall sponges can become almost bone-dry if you wring too hard, so wring the sponge so it is not sopping but still noticeably damp. The sponge needs to be damp enough to dissolve and loosen the hardened joint compound.
Sand Joint With Abrasive Side of Sponge
Begin by knocking down any obvious high spots with the abrasive side of your sponge. Move the sponge in broad, circular strokes. Don't press too hard in any one spot, since this can create depressions in the joint compound. On this pass, just concentrate on the high ridges and the spiky areas of the dried compound.
When the sponge begins to bog down, rinse out the sponge and continue with a newly dampened sponge. Be patient. This part of the job will take more time than it does when dry-sanding, which quickly grinds down high spots with minimal effect on surrounding areas.
Sand With Smooth Side of Sponge
Wring out the sponge, then remoisten it and switch to sanding with the smooth side of the sponge. This is where you begin to feather the joint compound outward from the joints. This will reduce the visibility of seams after painting.
On this second pass, since you have already taken down the high ridges, you can concentrate on lowering the joint compound bump.
After this second pass, you are done. Any more wet sponging will get the drywall paper too wet. If two passes are not sufficient, you may need to dry-sand the joint compound.
Let the Wall Dry
Let the damp taping compound dry fully, then inspect the surface. The main value of wet drywall sanding is to smooth out and feather those ridge edges. Compare the "before" joint with the "after" joint. The "before" joint has a defined line. Running your finger across this line, you feel a definite ridge. On the "after" joint you will notice a smooth, hazy feathering effect.
One thing that wet sanding does that dry sanding does not do: It moistens dried mud compound, thus "re-activating" it and moving it to other parts of the wallboard.