Plaster walls were often constructed in homes through the late 1950s until drywall replaced plaster as a wall covering. While plaster may need to be replaced by a professional contractor if excessive damage is noted, you can fix cracks on your own. Cracks can be easily filled in with lime-based plaster material. However, quick repairs rarely last. You will need to do several things before the repair is made to make sure that plaster remains after your fix is completed. A few of these things are outlined in this article.
Investigate The Crack
Plaster cracks form for a wide variety of reasons and the cause of the crack should be investigated before repairs are made to make sure that new damage does not pop up. Smaller cracks around windows and doors are often due to the home settling. Specifically, the earth settles, which causes the foundation to move a bit and cracks to appear along load-bearing walls. Similar cracks are likely to be noted due to the shrinkage of the foundation or the plaster itself. Smaller diagonal cracks may be seen too if a large amount of weight is placed against or above the wall. For example, damage may be noted along the wall on the first floor if you place a heavy dresser in the second-floor bedroom above it. All of these cracks are typical ones that appear under normal circumstances and probably will not return after they are repaired, so go ahead and fix them yourself.
However, if you notice a crack near a window or door that seems to widen slowly over time, then the plaster may have pulled away from the lath material. A fairly large amount of plaster may need to be replaced and reattached to the lath underneath. This is probably a job that a specialist should be contacted for.
Also, if you notice long and jagged horizontal cracks that run the length of foundation walls, then this may indicate a foundation problem or a water damage issue. If the cracks are seen along a single wall and if you also see that the plaster appears darker around the damage, then this indicates that water damage has occurred. A roof leak or a general plumbing leak is likely. Make sure the leak is located before you fix the wall. Also, the plaster wall should dry completely beforehand. It should only take a few days for the plaster to dry. Plaster will feel cool to the touch when it is still wet, so make your repair once the plaster feels room temperature to the touch.
Reveal The Wood Lath
If you note spiderweb types of cracks along your plaster wall, then you may be tempted to simply fill in the cracks with some joint compound or plaster filler. However, the filling material will not properly bond to the lath underneath the plaster. The fill material will then likely bulge out and a new crack will appear. To prevent this, you will need to reveal the lath under the damage before your repair is made. This will help to establish what is called the key-ways, or the bonded plaster layer that sits in between the laths.
To reveal the lath, use a tool like a five way or paint scraping tool to release the plaster. Run the flat blade through the crack to release loose material. Rock the tool back and forth in the crack as well to release a bit of extra plaster until you can see the wooden lath underneath. Use a damp cloth and your vacuum to clear out the crack. You will then need to dampen the lath and place a base compound across the wooden slats. A two-part plaster repair kit will have the base key material and the plaster repair compound. Use the crack repair on top of the base only after it dries completely.
If the crack is too big or complicated to repair on your own, contact a company like Painting By Jerry Wind for professional assistance.