If you are a homeowner doing some DIY work or finally finishing your basement, you are probably wondering what kind of materials to use.
You have probably have seen drywall and drywall mud used on framed wood walls, but can you use drywall mud on concrete?
Drywall mud is not an ideal material for concrete since it is water-soluble and is likely to have problems down the road, especially if there is any moisture whatsoever in the concrete. It’ll discolor and peel quickly in most cases.
However, it is possible to use drywall mud in some cases with specific techniques and steps.
This article will give you some pointers on why drywall mud can fail in specific scenarios.
Read on to get the information you need to decide whether drywall mud is the right choice for your concrete surface and what other options are suitable for the job.
Table of Contents
Why Is Drywall Mud Not Good On Concrete?
Drywall mud will tend to lose its adhesion, deteriorate, discolor, and peel over time when exposed to moisture.
Drywall mud (sometimes referred to as joint compound) is mainly composed of gypsum powder mixed with water to form a highly workable paste.
This is what makes the material water-soluble.
Any dampness at all will decrease the effectiveness of this gypsum-based paste by weakening the bonds at the interface between the concrete and drywall mud.
In a warm and humid environment, condensation is more likely to form on the surface of the concrete.
In addition, basements with concrete foundation walls are often the most humid part of the house due to poor insulation and ventilation.
If you live in a humid climate or the walls, you are using the joint compound on are basement foundation walls; this is a recipe for disaster in terms of the long-term quality of the work.
It will eventually show signs of hairline cracks or, even more apparent, thicker cracks, peeling away from the wall, and/or splotches of discoloration.
In addition, if the mortar joints (the spaces filled with mortar in between concrete blocks) crack, this will also cause your drywall mud layer to crack.
Drywall mud is most commonly used to seal drywall joints, on drywall repairs for holes and cracks (similar to spackling paste), and to cover joint tape on drywall seams.
It is not designed for coating concrete walls and is not the ideal material for this job.
If you are doing a skim coat on a concrete ceiling, the drywall mud will work for this initial thin layer if mixed to the right consistency and followed with other sealing coats.
How To Best Use Drywall Mud On Concrete
One option is to start with a skim coat of concrete filler and then apply the drywall mud.
Adding a fiberglass mesh layer between the concrete filler and drywall mud will also help.
In addition, applying the coats of drywall mud in skinny layers is more likely to be successful.
It is always important to properly prepare your surface before you apply the first coat of drywall mud.
Use a drywall knife to remove loose cement, grout, or other debris.
Use a paint scraper to remove any existing paint on the concrete.
After applying the thin coat of drywall compound 4-8 times using wide drywall knives, this layer of drywall compound can function as a base for paint once it has been sealed.
Sand and paint over these layers with a primer and finish paint.
If you are in a pinch and plan to apply drywall mud on a concrete block wall, these steps will help you increase its longevity.
However, it is still not guaranteed your joint compound won’t eventually deteriorate if exposed to moisture and large temperature fluctuations.
It’s best to use something else.
For more concrete covering ideas, check out our guide on how to install drywall in garages.
What Type Of Material Should I Use On My Concrete Wall?
Options such as sheetrock, plaster, and stucco will function better on concrete walls.
Below is some information showing the difference between drywall mud and other common building materials.
This chart will give you an idea of their advantages in different scenarios:
| Material | Properties |
|---|---|
| Plaster | Versatile material, highly workable, used inside or outside, generally requires more experience |
| Stucco | Intended for outdoor use, often more durable than plasters, rougher texture, porous/absorbant |
| Sheetrock/drywall | Good insulation, not ideal for curved walls, cheaper to install, needs extra layer/sealing before covering concrete, smooth surface |
What Will Drywall Mud Stick To?
Drywall mud sticks well to any type of rough-grain wood surface, plywood, and oriented strand board (OSB).
If applied to painted wood, make sure the paint is non-glossy.
Even semi-gloss paint will prevent the joint compound from sticking correctly and must be sanded or scraped.
The drywall compound should also not be applied to wood with high water exposure, such as outdoor applications or near sinks.
It works best when it is applied in thin coats.
Drywall mud sticks exceptionally well to porous surfaces, and it is sometimes applied as a skim-coat on plywood walls.
Plywood sheets still need to be taped similar to the sheets in drywall installations to avoid cracks.
Can You Use Drywall Mud Outside?
For skim-coating large surfaces, such as an outdoor shed or other structures, drywall mud will not hold up when exposed to the elements.
For outdoor purposes, one good option is to coat the sheets of drywall multiple times with water-based urethane to make them waterproof.
Joint compound will also last longer in exterior settings if it is protected from rain and moisture or covered with another type of siding.
The best type of drywall mud for outdoor use is called a setting-type joint compound.
This type of drywall mud is designed to dry quickly and is moisture-resistant.
However, moisture-resistant joint compound is still not completely waterproof and will deteriorate when wet or high humidity.
Related: Why does drywall mud mold?