Plaster Wall Repair

Plaster wall repair can have two different methods, one being the actual use of plastering material for authentic restoration and the other for a purely functional repair involving placing sheet rock in place of the damaged plaster for the repair.

The problem with old plaster is, once it gets to cracked it can begin to crumble with the slightest disturbance in attempts to repair it. Both methods can have satisfactory results, but the one involving drywall will be easier for most people.

The traditional plaster repair involves removing any loose plaster and one can leave it in most any shape, as long as the lath is still in place, which will not matter when applying the coats. This is a 3 step process involving a scratch coat, an intermediate coat and the finish coat for the final blend in addition to the repairs of the wood lath before this process, if necessary.

On the other hand, a drywall repair will have to have the loose plaster cut out in whatever square size needed with straight edges to the framing to accommodate the new piece of drywall.

My focus here is on using the drywall method to make repairs of loose or missing plaster. If you are just needing to fix cracks in plaster, my steps on Drywall Crack Repair will work the same way on plaster as it does with drywall.

With any taping repair with a glossy surface, painted drywall or plaster, wash the area with Dirtex or TSP first and then prime with a good paint primer before applying mud for better adhesion, especially in a kitchen where there may be more chances of grease buildup around the stove area. This would apply to re-painting too.

The average thickness of plaster without the lath backing is about 3/8  inch, so this the right thickness of drywall to get. Some plasters are quite soft and some are very hard, most is the hard kind, so cutting a fairly straight line can be a challenge. If it is the soft plaster, you can use a utility knife, even though you still go through a few blades.

There are two methods that will work on hard plaster, one being, to use a 2 inch sharp cold chisel and a hammer and the other is cut it with a 4 inch power grinder fitted with a diamond blade. Now you probably do not have the grinder but it can be bought for around $65.00, and while it is very dusty, it is a lot easier. The hammer and chisel method may loosen more plaster that you are trying to save.

Locate the framing, studs or joists, and draw your lines in a square or rectangle shape for as large as area as needed to replace the bad plaster. Most old framing is almost 2 inches wide so there is much wood to “catch” so that the screws will secure the drywall properly, you want to screw into the framing to hold the new piece tight.

Be sure to draw the area out so that it is square, that is 90 degree angles. Once the perimeter is cut, you can knock out the inner area with a hammer, clean the edges and place the new drywall piece in by screwing it to the studs.

At this point the 3/8 inch drywall will be pretty flush with the rest of the surface and now can be taped smooth with no major difference between the new and old surface. The closer you can get to matching this up, the easier it will be to make the patch blend in and less mud finishing when coating.

There are two more methods to consider if the plaster is to far gone and would require a lot of work, and that would be to remove all plaster and lath and install new 1/2 inch drywall directly to the studs, or sheet over the entire surface with 3/8 inch drywall for a totally new surface that will be trouble free in the future.

Removing the plaster entirely will be almost necessary if you plan to re-frame or move a window, or door, or are needing to repair any weak or cracked ceiling joists, might as well take it all out and make the walls and ceiling look good when finished.

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