Wet Sanding Drywall: 9 Dos and Don’ts for the DIY Project
When it comes to interior walls, drywall has a lot going for it. It’s inexpensive, relatively easy to install and repair, and can withstand life in the average household. However, drywall requires a fair amount of sanding before it can be painted – unless you like the look of bumpy, lumpy walls with visible folds between the grout. And sanding drywall means dust. So much dust that you might be tempted to build with Medium Density Fiberboard (MDF) instead. While MDF doesn’t require as much sanding to get a nice, smooth surface for the paint to have, it does not respond well to fluctuations in humidity and has a tendency to tear from expansion and contraction.
Fortunately, with the right technique, you can wet drywall with sand to reduce dust and still get an ideal surface for paint. Read on for professional tips so you know what to do – and what not – to get error-free results.
Wet sanding is time consuming: if you are in a really hurry to prepare drywall work for the paint, dry sanding is better. Remember, however, that when you dry sand, you still spend a lot of time removing the dust. Wet sanding drywall requires minimal cleaning, so the total time for both methods is comparable.
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Don’t expect perfection.
Wet-abrasive drywall generally leaves very slight waves in the finished surface due to the flexibility of the drywall sponge. This can be used to your advantage when touching up a textured wall. It’s much easier to match the texture with a damp sponge than it is with sandpaper. Just use your sponge to dab, wiggle, and blot the drywall mud that is covering the tape holding the sheets of drywall together until it matches the texture you want to duplicate.
Don’t skimp on the water.
Wet sanding requires a lot of water. So use a 5 gallon bucket and fill it three-quarters full with warm water to soften the drywall mud. That way, you won’t have to stop and refill your bucket too often.
Use the correct sponge.
While any stiff sponge does the job, you’ll get the best results with a drywall sponge specifically designed for wet sanding (like this one available on Amazon). These specialty sponges are thick and stiff, with one side being slightly abrasive for the first sanding pass and the other side being soft and fluffy for the second pass to smooth out the drywall mud.
Fully submerge the sponge in water until it is soaked, then squeeze out the excess so the sponge gets damp but doesn’t drip. If you’re sanding a full wall, have two or three sponges handy in case one wears too much or cracks during use. A drywall sponge should be sufficient for small repair work.
DO NOT rub too hard.
Wet sanding drywall is a bit of a hassle, but resist the temptation to speed up the process by aggressively scrubbing on lumps and rough spots in drywall mud. This can create craters and holes that you have to fill in the end. An overzealous approach can also lift or tear off the drywall connector tape under the mud.
Focus on the bumpiest areas.
Start with wide, gentle strokes to soften the entire stretch of drywall mud, then focus on the uneven or ridged areas. Use circular motions to remove the imperfections. Let the sponge and water do the work – not the strength of your hand. Try to remove imperfections without creating valleys or holes.
Don’t forget to rinse and rewet.
As you work, your sponge will collect drywall and sludge, reducing its ability to clear imperfections. Remember to thoroughly rinse your sponge in the bucket of water if it gets too dirty and then squeeze out any excess water before returning to your task.
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Change the water as needed.
The water in your bucket will turn milky and thick after rinsing the sponge several times. Throw away the cloudy stuff and refill the bucket with fresh water to make cleaning your sponge easier. When you pour the water down the drain of your kitchen sink, flush it with hot water to prevent buildup in the pipes.
Do not make more than two passes.
The worst burrs and bumps should be removed on the first pass with the abrasive side of the drywall sponge. On the second pass, focus on smoothing the edges of the drywall mud and using the fluffy side of the sponge to achieve the most perfect surface possible to minimize small imperfections.
If two passes are not enough, you will need to let the drywall dry and then use sandpaper to complete the job. Repeated wet sanding after two passes will soak the drywall too much and lead to craters, valleys and melted spots.