I often find myself working on older homes. My own home was built in 1952. Like most older homes, the walls are plaster. The walls in my home are plaster over plasterboard or rock lath. If you haven’t run into rock lath, it’s essentially drywall, but with a bunch of holes, which hold the plaster in place. The alternative might be plaster over wood lath or metal lath.
Trying to cut holes in this stuff can be tricky. The first time I wanted to mount a recessed lighting can, I tried a hole cutter on a drill. It worked, but the (pricey) hole cutter was trash, by the time I finished the hole. I also tried a variety of bits on my Roto Zip. They didn’t fair so well, either. And, they were slow. They glow a bright red, as they heat up. At least, it makes the job more interesting, if you don’t mind catching the house on fire.
When I wanted to add a skylight in the kitchen ceiling, I was faced with the daunting task of cutting a 4’x4′ hole in my kitchen ceiling. I was thinking about the various tools (that I own) that might get the job done. My first inclination was to use a concrete blade on a circular saw. I imagine that would get the job done, but the dust would be incredible. Plus, using a circular saw upside down to cut the hole in the ceiling didn’t sound like a ton of fun, either.
I couldn’t think of any hand saws that would stand up to what’s basically a cement ceiling. A chisel would be slow and make a mess of the hole. I also have an old Rockwell SonicCrafter oscillating saw. I tried it with a grout cutting blade. I worked, kinda. It was slow and trying force that blade into a full-coat plaster surface wasn’t exactly ideal. At that rate, I wasn’t sure I’d live long enough to finish the job.
Perusing the mess on on mess work bench, I came across a new 3/8th inch concrete bit that was about 20″ long. It stood out since it was unusually long and it was unusually new. (most of my cement drill bits look like they been abused, which they probably have been) Of course, a new cement drill bit can punch through the plaster in a blink. So, my solution was to mark my line for my opening. Then, following the line a punch a series of holes about a 3/4 of an inch apart. The extra length on the drill bit meant I didn’t to use a ladder. I just drilled one hole after another. After I perforated the ceiling, I used the grout cutting blade on my oscillating saw to connect the dots. It went surprisingly fast and I ended up with a pretty decent line. It wasn’t smooth, but it was consistent and there was no additional damage to the surrounding plaster. I was easily able to create a finished edge using standard drywall corner bead.
I’ve used this technique again, while opening large holes for a Solar Tube and a bathroom vent. It’s worked well each time.
Hopefully, this idea might give you a new approach if you’re faced with the task of opening up a plaster wall or ceiling. It’s still a face-full, but it works well.