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If you have concrete walls you’re trying to smooth out, you might think that covering them in a coat of drywall mud will do the trick.
Will drywall mud stick to concrete?
This depends on many factors, including the humidity levels, the type of drywall mud you use, and the prep work you do beforehand. To increase the odds of drywall sticking to the concrete, you’ll need to apply several thin layers of joint compound and then prime and paint.
However, even with the necessary precautions, the drywall compound may eventually crack and fall off.
Here’s everything you should know before you get started on this home renovation.
How to Apply Drywall Mud to Concrete
Drywall mud works best on concrete in dry rooms with low humidity.
If you’re trying to skim coat damp basement foundation walls with joint compound, you’ll likely be disappointed by the outcome. In this case, using sheetrock is a far better option. Other options include plastering or using stucco on the walls.
However, if you weighed the pros and cons and determined your walls are good candidates for DIY drywall skim coating, you can get started with some prep work.
Here’s what to do:
- Use a scraper or masonry chisel and hammer to knock out any high spots in the concrete
- Clean the wall with a wire brush
- Wash the wall with a damp sponge
Now, with the wall still damp, start at the top and apply a very thin coat of drywall compound, packing it into the cracks and crevices. Move your trowel back and forth in different directions, working it in.
Scrape off the excess as you go so you’re left with a smooth surface. Allow the first coat to dry for 24 hours, and then add another very thin coat to the wall.
Allow the second coat to dry, and then use a scraper to scrape off all the high spots in the joint compound.
Repeat two more times, scraping in between layers.
Once you have four thin layers on the wall, you can decide whether you need to add more or if your wall looks ready to be sanded and painted.
If your wall looks ready, lightly sand using 120 grit sandpaper or a fine-grit sanding sponge until the wall feels smooth and even. (If you use a sanding sponge, dampen it with water first.)
You can then wipe down the wall to clean off the sanding dust.
Afterward, using a high-quality primer on the wall before painting.
How Thick Does Drywall Mud Need to be on Concrete?
When applying drywall mud over concrete or cinder block, you need to do it in several thin layers. Each layer should be approximately 2-3 mm in thickness.
It can take anywhere from 4-8 of these layers to thoroughly coat your concrete walls.
What is the Best Joint Compound for Concrete?
One of the best joint compounds to put on concrete is Durabond.
You can find Durabond at the Home Depot and other home improvement stores. It has high humidity resistance and doesn’t crack as easily as some other types of joint compounds do.
When choosing a joint compound, look for something with a strong bond suitable for humid environments.
Will drywall mud stick to concrete? Yes, but there’s no guarantee.
You also need to make sure your drywall is still good before applying it to the concrete walls.
If you’re trying to skim coat over concrete block walls in a damp basement or you live in a humid environment, there’s a good chance that drywall mud will eventually crack and fall off your walls.
However, if your basement is dry and you take your time applying several thin layers of high-quality joint compound, you may be surprised by how good your concrete walls look and feel.