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.
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.)