I'm trying to mount a TV in my basement. House was built in the 60's, and the basement used to be a bomb shelter, from what I've been told, but most of the cinderblock walls were taken out. I'm trying to mount my TV on the wall, and when I drill in, I drill through the drywall, before hitting a hard spot. With a wood drill bit, I can apply extra force, and it will force in, but soon after, I hit a hollow area. I can't get lag bolts to tighten, as they start to go in somewhat tight but eventually I start feeling a grinding sensation and they end up getting loose before they are fully in.
Am I drilling into old Cinder block? It doesn't feel like the hard area I'm drilling in is very thick… maybe 1/2-3/4 of an inch, which seems too thin to be a cinder block. TV is ~70 pounds, am I safe to mount it there? Should I use anchors? One side of the TV will be mounted into a standard wood stud, so will that likely provide enough support?
Best Answer
Cinderblocks, as you call them, are also known as concrete masonry units (CMU). The “wall” thickness of CMU’s is 1 1/4”, so it’s probably not CMU’s if you think it’s 1/2” - 3/4” thick.
Could be plaster...it’s about 3/4” - 7/8” thick. Or, it could be thin coat plaster over wallboard. Usually the wallboard is 1/2” thick and very hard (dense) plaster about 1/16” thick is applied directly to the wallboard.
Plaster, thin coat plaster, wallboard, etc. are not structural and would not be suitable to support your TV.
I’d look for another stud and follow the manufacturer’s recommendation about connecting into studs. (Do they give an alternate installation layout using a piece of plywood that spans from two studs?)