Tips for Working on Plaster Walls
If you live in an older house, say 50 or 60 years or older, there is a good likelihood that you have plaster on your walls. Plaster walls were very common, especially in the late 18th century and 19th century. Plaster was fairly readily available, was workable, and was capable of producing very smooth walls and ornate embellishments. It was and is however, very difficult to worth with. It took a fine plasterer many years to learn his trade under the careful instruction of a master plasterer.
Plaster is still widely available, though rarely used. Just check the painting aisles of your local home improvement center and you'll see it mixed in with spackle and patching compound. The reason for its demise was the invention of joint compound. Unlike plaster, joint compound (or drywall compound) is easy to work with. It is slow to set up and harden, is very easy to sand, mixes easily, can be purchased already-mixed, and is easy to clean up. Joint compound works by simply letting the water evaporate out, leaving the hard, white stuff on the wall.
Plaster, on the other hand, sets up quickly, hardens like cement, is very difficult to work with once it starts to set up, is hard to clean up, and must be mixed up as needed and in quantities that can be worked with quickly. Plaster as it sets up, is actually a chemical reaction between the solid plaster and the water.
For this reason, joint compound is the natural choice for most new homes and patching jobs. However, plaster is by far the superior product. A plaster wall is rock hard, has a solid sound, and feel, is not easy damaged or scratched, and can withstand some abuse. These properties make for some interesting remodeling and repairs.
A simple task such as hanging a hook for a picture frame can cause large chunks of plaster to break free from the wall and come crashing down. Try to drive a drywall screw into plaster can be an exercise in frustration as chunks break out of the wall and the screw getting dulled by the plaster, Drill bits and saw blades dull instantly on contact.
Because of these challenges with plaster, I have compiled a few tips for working with it. Be aware, that these work for me in most situations, but plaster can be different and behave differently in different locations, so work very carefully.
1. When hanging a picture frame from a hook with a nail in it, first tape a large piece of masking tape over the area where you will drive the nail. This will help prevent chip-out. Once the nail is in place, remove the tape.
2. Another way to insert a wall hanger for a picture frame is to drill a small pilot hole for the nail. The pilot hole need not be deep. Just deep enough to penetrate the topcoat of plaster. If you see brown dust coming from the drill bit, you are through the topcoat and into the brown coat.
3. To drive a screw through plaster, always drill a pilot hole!
4. Never use a drywall screw in plaster to hold anything! Even though it may seem that the plaster is holding it in place, you risk tearing out a large chunk of plaster should you find a weak spot. Always screw through the plaster and into the studs.
5. When screwing through plaster and into the wall studs, make sure you are into the wall studs and not the wood lath that holds the plaster on the wall! Pulling down lath is one of the worst things you can do, as it will pull down large chunks of plaster with it!
6. Standard stud finders don't work on plaster walls. You need stud sensors that feature some sort of deep penetrating technology. Common stud finders are designed for half-inch drywall walls and can distinguish plaster thickness very well.
7. Use the tapping technique to find studs. Plaster has good harmonics and by tapping or rapping it with your knuckles, you can usually hear the hollows between the studs fairly easily.
8. Like anything else in an old house, be extra careful! There weren't building codes when many of these houses were built so there is no guarantee that you wall studs are evenly spaced, that there aren't old pipes in the walls, or that abandoned and antiquated plumbing and electrical lines exist in the walls.
Remember, work slowly and smartly! Never rush an old house project. Take a few minutes to think things out several times. You will still run into surprises, but if you work slowly and deliberately, hopefully, they won't ruin your day!