Can Sheetrock Mud Be Applied Over Paint?

Warning

• Joint compounds of all types adhere well to most surfaces, provided the area is firm and clean. But don’t use joint compound to cover painted wood, metal, ceramic tile, cement, stone, brick or other surfaces besides drywall or plaster. The joint compound initially will bond well, but the expansion and contraction these materials undergo due to temperature changes might cause the joint compound to crack and chip away later.

Dirty or Damaged Surfaces

• Don’t apply joint compound over a surface covered with dust or where the drywall is breaking apart. While the joint compound will bond successfully with the surface you cover, the loose material will slough off and lead to blistering. Similarly, don’t apply joint compound over blistering, cracked or peeling paint. The joint compound forms a bond only with the topmost surface, so a weakened coat of paint can lead to future problems, such as bubbles and cracks.

Glossy Surfaces

• If the painted surface you plan to cover with joint compound is as slick as, say, a car’s finish, roughen the area with 120-grit sandpaper before applying joint compound. The tiny scratches will improve the compound’s ability to adhere. Extremely glossy paints are rare in home interiors, so most projects won’t require this step.

Considerations

• If you’re unsure whether you need to roughen an area to prepare it for joint compound, choose an inconspicuous test location. Mix the joint compound according to the manufacturer’s directions. Apply a thin coat over the painted area. Allow your application to turn bone-white, which indicates the compound is dry. This typically takes 12 to 24 hours, depending on temperature and humidity levels. Examine the dried joint compound, looking for blisters or cracks. A few small blisters or cracks don’t indicate a problem, but many blemishes across the entire surface of the area might mean the joint compound is not bonding well with the painted surface. In this case, roughen the area slightly with 120-grit sandpaper and apply again.