Filling Wall Cracks Step-By-Step

cracked concrete
  • 4-24 hours
  • Intermediate
  • 20-60
What You'll Need
Silicon-based latex caulk (for plaster)
Caulking gun (for plaster)
Clean rag (for plaster)
Putty knife (optional)
Concrete epoxy or super glue (for concrete)
Spackling knife (for concrete)
Heavy brush (for concrete)

Interior and exterior walls sometime form cracks that need to be filled. The type of wall repair you will have to undertake depends, of course, on the type of wall. Indoors, homeowners may be confronted with plaster wall repair, while outside a concrete wall waits to be fixed. Whatever the type, there are simple and effective ways to patch any cracks that may occur.

Tools and Materials

For plaster:

  • Silicon-based latex caulk
  • Caulking gun
  • Clean rag
  • Putty knife (optional)

For concrete:

  • Concrete epoxy or super glue
  • Spackling knife
  • Heavy Brush

Step 1: Clean the area to be patched thoroughly

Plaster: Make sure there is no debris in or around the crack to be patched. If there is anything hanging from the wall that could present an obstacle, remove it for the duration of the work.

Concrete: Same goes for concrete, but since it is outside, more dirt and debris might have accumulated. Before patching, prepare the surface by cleaning it thoroughly with a jet setting on a hose or even a pressure washer if you have one. Go as far as scrubbing the area with a heavy sponge if you have to. You want it very clean!

Step 2: Prepare the filling agent and apply it

Plaster: Once the silicon caulk tube is in the caulking gun and ready to go, have a small bowl of water and the clean rag handy. If the crack is small, squeeze a bit of the silicon onto your finger (wear a latex glove if you have sensitive skin) and gently work it into the crack. For larger cracks use the putty knife. Don’t apply too much because you want the silicon to as closely match the paint as possible. Dip the rag lightly into the water and gently work it into the caulk in a circular motion. Again, for small cracks, you don’t need much. Be a little more liberal with large cracks.

Concrete: Depending on the type of epoxy you have, work in the first layer with either a brush or a spackling knife. If the crack is deep, it is probably better to use a brush. Don’t slather it on in one thick coat, for it could pull itself away from the wall if you do. Rather, apply several thin coats, giving each one time to adhere to the surface and properly fill in the crack.

WARNING: Some epoxy products release fumes as they dry, so check the container's safety instructions and make sure your work area has proper ventilation.

Step 3: Smooth over the final coat

Plaster: Chances are with plaster you will only need one coat to fill a crack. The process of smoothing over the silicon caulk is mostly done while you apply it, but give it a once over with your finger. After it dries you can touch up the paint to hide the repair.

Concrete: After the final coat has been applied–not too quickly, so it sets–brush over the repaired spot with a clean, slightly damp brush to get the texture to match the rest of the wall. If wall color is a consideration, let it dry and paint over your work.