Cracked Plaster Wall

Tools:

flathead screwdriver
5-in-1 painter's tool (or putty knife)
vacuum cleaner
gloves
sponge
ceramic tile mastic
water putty
wall tile adhesive or water putty
medium-grit sandpaper

1. First determine that you are working with plaster and not drywall. The easiest way to tell is by removing an outlet cover and examining the wall's construction (figure A). Plaster is hard and looks like it has cement in it. Drywall is powdery and the surface is easily dented.

2. Use the painter's tool or putty knife to scrape away loose material from cracks (figure B), then use the vacuum to clean loose debris from the area. It's important to remove all dust and debris, otherwise the patching material will not bond with the wall and fall out.

3. Dampen crack with sponge to prevent plaster from sucking moisture out of new fill material (figure C).

4. Apply wall tile adhesive with fingers and work it into the crack. Once that's done, load up the painter's tool or putty knife with adhesive and run it over the crack to make the material flush with the surface (figure D).

5. The adhesive is flexible and will resist cracking, but excess adhesive cannot be sanded flat once it dries. Therefore it's very important to make the adhesive smooth and flush with the wall before it sets up.

6. Allow the adhesive to set for about four hours. If it shrinks, come back and add more adhesive.

7. Once the crack is filled, clean up around the edges with a damp sponge. Dab the edge of the sponge on the crack to create a textured appearance to match surrounding wall if necessary.

8. Water putty is another option for filling plaster cracks. It's not flexible like the adhesive, but it will not shrink when drying.

9. Mix up putty to the consistency of thick gravy, and use the painter's tool to work it into crack (figure E). Work quickly as the putty sets to the touch in about 10 minutes. Go back and add more if necessary, and once the putty dries smooth out the surface with some medium-grit sandpaper.

10. Once water putty patch is dry, cover it with a stain blocker and primer before painting otherwise the putty will show through paint.