How to Patch Deep Holes in Plaster Walls

When remodeling an older home with plaster walls, you can keep the budget down and retain a certain period charm by repairing the plaster rather than removing it all. Cracks and other damage to the plaster often go all the way to the lath or brick underneath and can be more difficult to patch than drywall. In following the steps in this article you will be able to repair most any damage to plaster in your home.

Difficulty: Moderate

Instructions

Things You'll Need:

• Drywall of various thickness
• 45 minute drywall mud
• Drywall joint compound
• Plaster patch
• trowel and scraper set
• electric drill
• drywall screws
• liquid nails
• sanding blocks
• hammer
• chisel
• shop vac

1. 
    
   Putty Knife

   The first step to patching and repairing the plaster in your home is to remove any cracked or damaged plaster. Use your hand or a small putty knife to test all wall surface areas for cracks or damage. In any place that you find crumbled or cracked plaster, remove carefully any loose plaster all the way back to the lath or brick wall. Beware of using your putty knife as a wedge behind plaster as you may inadvertently remove salvageable plaster.

2. Now that all of the broken and damaged plaster has been removed, use a shop-vac to remove all dust and small debris. Assess the damaged area. If it is large ( more than a few feet wide or tall), deep (more than half an inch, and slightly regular in shape, consider using drywall as a base. If you are able to use drywall, screw it into the lath or use liquid nails to attach it to the brick behind the old plaster. Use drywall pieces that are at least 1/8'' thinner than depth of the hole. For instance, if the hole is uniformly around 3/4'' deep, use no deeper than 5/8'' drywall. Do not worry about making the drywall the same size as the hole as you will be filling the gaps with a patch regardless.

3. Now that the hole is ready to patch, lightly wet the surface with water using a spray bottle or cloth. Mix plaster patch in a small bucket or masons pan. Apply it to any areas of the wall where there are wide gaps. Use putty knives to push the plaster patch deep into each hole. In very large holes apply the plaster patch in several layers each no more than 1/2'' thick. When you have finished applying plaster patch to a hole, smooth it down with a wide putty knife to avoid having the patch thicker than the wall around it.

4. 
    
   Smoothed and repaired plaster hole

   Once the plaster patch has dried you can use 45 minute drywall mud to smooth over the patch. Mix it according to the instructions on the bag or consult with someone at your local hardware or home-improvement store. Apply the mud over any plaster patched areas that are not flush with the original wall, over any cracks or small blemishes that you can find. The 45 minute drywall mud dries quickly so make small batches and cover only a few holes at a time. Use a lighter grit sanding block after the mud has dried to smooth it out.

5. The final step in repairing your plaster walls is to use a slow drying thin drywall mud to fill in any remaining gaps or blemishes. You can use a premixed drywall mud and putty knives to add a thin coat over each of your patches. Let it dry for a day or so and then sand with a fine grit sanding block until the patch is perfectly flush with the surrounding wall. Vacuum off the dust and debris and you should have a perfectly smooth plaster wall.

Tips & Warnings

• When painting be sure to use a stain blocking primer such as 'Kilz' to give a clean palate