Repairing Cracks in Plaster Walls
If you have plaster walls with wide cracks, use a utility knife to clean the debris (crumbled or broken bits of plaster) out of the crack.
If it seems like the wall around the crack is warped, reattach the lathe by nailing nails through both the plaster and lathe. Then the cracks can be filled.
If you purchased the plaster paste as a powder, mix according to the directions on the package. Using a putty knife, fill the cracks with a small amount of paste at a time. Sometimes, if the crack is very tiny you can apply the paste with a butter knife.
Let the plaster dry for several hours and preferably overnight. Take a piece of fine grained sandpaper and sand the area to remove any excess plaster until the wall is smooth. Then you can paint or paper the wall.
You will need to use mesh tape or joint tape for a very wide crack for the plaster paste to stick properly and effectively repair the crack.
Cut enough tape to cover the crack and extend a few inches in each direction. Use more putty and a wider putty knife to push the paste deep into the crack using diagonal strokes that cross perpendicular to the crack.
For a wider crack you definitely want to wait until the following day to sand and paint.
Repairing Cracks in Drywall Walls
Cut out a trench slightly larger than the crack and then brush it with a paintbrush to get out the chalky dust and dirt where the drywall has cracked or been otherwise damaged.
Fill the hole or crack in the drywall with drywall spackling putty or joint compound.
Apply the compound in two stages as drywall can withstand more sanding. First, fill the crack or hole with the putty or joint compound. For small cracks and holes you can probably immediately sand the surface with a fine grained sandpaper.
A second application of the putty will make the surface identical to the rest of the wall.
Just as with wider cracks in plaster walls, a very wide crack will need a little more structure to stick properly. This is where patching tape, also called mesh tape or joint tape, comes in handy. Cut enough to cover the crack and extend a few inches in each direction. Now use more putty and a wider putty knife to push the paste deep into the crack using diagonal strokes that cross perpendicular to the crack.
After you have sanded the patched area smooth you can paint or wallpaper.
Things You Will Need
- For plaster cracks:
- Plaster paste in powder form or premixed
- Putty knife
- Patching or mesh tape for wide cracks
- For drywall cracks:
- Spackling putty or joint compound
- Utility knife for clearing out debris
- If you wrap the sandpaper around a piece of scrap wood, you can make a flat surface and avoid forming trenches or dips on the wall.