Question: We’ve removed old plaster from large areas on a wall and we wanted to know if you can you apply new plaster to these areas over the old wood lath?

Plasterman’s Answer: It can be done, but I don’t recommend it. When wet plaster is applied to and sets over the old, dry wood lath, the wood can break during the drying time due to the plaster shrinking. This occurs hours after the finish has been applied. But that being said, it is possible to avoid this by wetting down and soaking the wood lath the night before. It is stronger and preferable to use metal lath attached with lathing nails to the existing plaster and lath. It allows the plaster to have more to hang on to and ultimately, you won’t be able to notice that the lath is any different than the rest of the house.

Question: How do you remove marks off colored plaster?

Plasterman’s Answer: Fingerprints and other marks on the wall can be very difficult to remove. One possible solution is to sandpaper the offending marks off the wall. You will want to be careful not to damage the wall in the process.

Question:How do you remove mold or mildew on plaster or stucco?

Plasterman’s Answer: You can use a light solution of TSP (Trisodium phosphate) in a hand held sprayer. TSP can be purchased at a local home improvement store like Lowes or Home Depot. Mix about 1/8 cup in a gallon of water. Spray the surface and let it set a few minutes and then scrub the affected area with a scrub brush. Do a small test area first. You can increase concentration if needed, but always spot test before doing large areas. After scrubbing, wipe away dirt with a clean wet rag. This solution can be used to clean any cement or lime based product indoors or outdoors.

Question: How do you fix small cracks in plaster?

Plasterman’s Answer: Run a pointed tool through the crack and just open it up slightly. Wet the crack 3 or 4 times with clean water using a small painters brush. Then fill it in with a quick setting finish coat. Never put retard in the patching material as patching plaster should harden as quickly as possible in order to set before the old plaster has a chance to draw moisture out of the new material. After the cracks or patches have been filled, wipe the area worked upon with clean water to remove the residue of lime and plaster left on the old plaster.

Question: Do you fix large cracks in plaster the same way as large cracks?

Plasterman’s Answer: No, there is a little more involved. If you need to repair badly cracked ceilings or walls, first examine the area on each side of the cracks for looseness. If the plaster is loose, it must be removed until a firm area is found. If a crack is large, it is best to remove the plaster to a width of about 6” on either side of the crack and remove plaster right to the lath or masonry. Cut and place a strip of metal lath to fit the area. This piece can be held in place by lightly driving lathing nails into the existing plaster to the existing lath.

Question: If I try to remove the wallpaper, will it ruin the plaster underneath? Would it be possible to just put a new coat of plaster over the wall without removing the wallpaper?

Plasterman’s Answer: The wallpaper will have to be removed. The basic process to remove wallpaper is to remoisten the bond that holds the wallpaper to the wall. This can be done several ways. Interestingly enough, you can actually apply wet plaster to wallpaper, let it sit for awhile, and then start removing the paper. But this method and others like it are messy. Well, thanks to modern inventions, there is another way! I suggest you rent a wallpaper steamer (from your local rental store) and use it to carefully steam the layers off. After steaming a small area, you can use a scraper to help remove the paper. However, you will need to be careful not to gouge or nick the existing plaster. Once the paper is removed, you will want to inspect the plaster wall to ensure that there are no loose areas. Loose areas will need to be repaired before continuing. If you do have a solid plaster wall with only small nicks from the scraper, these nicks can be fixed. You would do this by applying tape mud to them, letting the mud dry, and then lightly sanding these areas to a smooth finish.

Ask Us A Question

Have a question about plaster or stucco? Ask the PlasterMan here or ask our plastering community by posting in our Forum (See Gallery & Forum above)!