How To Repair Plaster and Lath Cracks?

What is Plaster or Lath?

Generally, in new houses, we see interior walls constructed of wooden studs to which large sheets of drywall are attached. Once nailed to the wood studs, a professional sheetrock installer will cover the seams with drywall tape, then a coat of plaster. It’s a soft mixture of sand and cement or lime with water, which is spread on walls, ceilings, or other structures, to form a smooth hard surface when dried.

The narrow strips of wood are lath, were nailed horizontally across the vertical studs. Lath is thin, flat pieces of wood that form a foundation for supporting plaster. It is a backing material used as a base or for groundwork. These laths are placed close together (about 3/8 inch apart). Once complete, several coats of plaster were layered on top to solidify the framework. Depending on the type of plaster, strength and durability may range once the coat is applied. The following are different types of plaster and lath that are used:


Ingredients for Plaster

Gypsum: Formed and settled by heating up a dried plaster powder with water. Durable, sound, and fire-proof.

Lime: Created by mixing water and sand the material provides a natural, mold-resistant, and breathable finish.

Cement: Cement-based plasters are strong and usually used for exterior structures, but can be lasting and endure harsh weather.



Ingredients for Lath

Rock: Similar to drywall, rock lath consists of a gypsum core of paper coverings that bond together to secure in place. It’s moisture resistant and can be simply attached, but can also easily develop long cracks.

Wood: The most common wooden-slat laths are still used in construction and come in narrow strips with spaces between each. The plaster is pushed through the spaces and fills the inside of the wall forming keys that hold the plaster in place.

Metal: Made up of steel and able to hold and withstand a greater amount of plaster than wood lath, resulting in durability.


Why your wall needs plaster?

  1. If you see unevenness or disbalance of wall surface or ceiling (even when plastered). This looks your wall rough. I suggest you look for some professionals to get it done or just an idea if you want to do it yourself.
  2. If you see your wall sagging, this might be the sign that the plaster is detached from the wall. If it is a ceiling, it may naturally slope. For that, you want to remove the entire plaster and apply new.
  3. No need to say what to do if the wall is cracked. Just call a professional or follow the DIY guide below.


How the Professionals of Painters Edmonton do Plaster Repairs:

Tools We Use:

  1. Utility knife
  2. Vacuum cleaner
  3. The premixed plaster repair compound
  4. Plaster Trowel
  5. Sandpaper
  6. Sandpaper block
  7. Ball pein hammer
  8. 10″ drywall knife
  9. Paint



1. Prepare the Crack

Initially, cut away the loose plaster with a utility knife. You can turn the knife to make the opening wider and more clean-lined. Remove debris while preserving the structural integrity of the surface around it. Clean away loose plaster and dust with a vacuum cleaner. You can also smooth damaged areas with a scraper.
Then make that portion wet.

3. Mix New Plaster

Once the surface preparation is complete, It’s time to mix up the required amount of plaster for the repair. Follow the instructions on the packaging to ensure the proper mixture. Mix it with the consistency of cake frosting.

3. Apply the Plaster Mix to the Damaged Area

Apply the mixture with the wallboard knife or trowel and spread a 1/4″-inch layer over the hole. Cross-scratch the first coat as it begins to set to allow the second coat to adhere well. You can apply the joint compound after applying the second coat.

4. Make smooth with a trowel or scraper

After you have applied plaster you can let it dry for a while, then use the plastering trowel to make it smooth and clean surface. You can also use the second thin layer of plaster.

Note: let it dry for at least 24 hours and spray water to make it harder.

5. Sand, Prime, and Paint

Lightly sand patch and let it dry. Then again, sand it one more time. Now you prime it with a thinned coat of high-quality latex paint or primer. When the primer is dry, paint the entire wall.

For more effectiveness, you can make holes around the prepared parts and use the plaster adhesive in the hole or you can nail the hole.

This is how we do, and you too can do.

If you think it is an easy job, it’s not but not hard. If you want to get it done the right way, you can call us. We aren’t just professional painters; we are also highly skilled plaster and drywall repair experts.

Here, at Painters Edmonton we provide almost all sorts of painting and renovation services including plaster repair service. Just call (780) 800-2022.

By: Royal Painting Edmonton. (Painters Edmonton)