Flat screen TV + crumbly plaster wall = bad idea? How bad?
March 31, 2022 8:41 AM Subscribe
I've got a 55", 37 lb flat screen TV and want to mount it on an interior plaster wall. The building is old (1950) and the plaster is crumbly enough that mounting a curtain rod left little holes around the bracket. I don't dare try to hang the TV myself-- if I go through with this, I'll definitely just get a professional installer. But is it a terrible idea in the first place to even try mounting a TV on this wall?
I figure that the weight of the TV will be supported by the studs instead-- so maybe the plaster itself and its crumbliness aren't even relevant here? I don't know. This situation must fall somewhere on a spectrum from "Don't worry, people safely mount TVs on walls like that all the time" all the way to "It's going to be a horribly tricky if not impossible installation and you should rethink your plans", but I have no idea what to expect. And there are probably other considerations and potential issues I haven't thought of.
Please be gentle with me as I have only the vaguest ideas about walls and how to hang things on them. Thank you hive mind for your patience!
I figure that the weight of the TV will be supported by the studs instead-- so maybe the plaster itself and its crumbliness aren't even relevant here? I don't know. This situation must fall somewhere on a spectrum from "Don't worry, people safely mount TVs on walls like that all the time" all the way to "It's going to be a horribly tricky if not impossible installation and you should rethink your plans", but I have no idea what to expect. And there are probably other considerations and potential issues I haven't thought of.
Please be gentle with me as I have only the vaguest ideas about walls and how to hang things on them. Thank you hive mind for your patience!
Best answer: As long as the mounting is on the studs I don't think it matters the condition of the plaster except for the amount of "touch-up" required after the installation.
But there are other questions need to be asked now. Have you considered the wiring? Will it rely on its internal antenna or will your cable box reach that? Or external antenna? Where's your entertainment center? Do you have a proper power plug for that wall? Etc. etc.
posted by kschang at 8:56 AM on March 31, 2022 [2 favorites]
But there are other questions need to be asked now. Have you considered the wiring? Will it rely on its internal antenna or will your cable box reach that? Or external antenna? Where's your entertainment center? Do you have a proper power plug for that wall? Etc. etc.
posted by kschang at 8:56 AM on March 31, 2022 [2 favorites]
And tbh, you can easily locate studs yourself on plaster and lath using a strong magnet to find where the lath is tacked to the walls with nails.
posted by Ferreous at 8:56 AM on March 31, 2022 [1 favorite]
posted by Ferreous at 8:56 AM on March 31, 2022 [1 favorite]
Best answer: Yeah, as folks have said, hit the studs and you should be fine. When you hire someone you might mention that you have crumbling plaster walls and ask what precautions they would take to minimize damage (putting painter's tape over the plaster before drilling would be one thing they might say).
posted by Rock Steady at 9:04 AM on March 31, 2022 [2 favorites]
posted by Rock Steady at 9:04 AM on March 31, 2022 [2 favorites]
You can also now buy TV stands that lean against a wall (example), which has the additional benefit of hiding cables while also avoiding holes.
posted by aramaic at 9:07 AM on March 31, 2022 [5 favorites]
posted by aramaic at 9:07 AM on March 31, 2022 [5 favorites]
Best answer: This isn't too dissuade you from hiring a profession if you choose to, but if you have a drill, tape measure, screw driver, level and the ability to lift the weight of the TV installation is pretty straightforward. I installed a mount with an articulated arm on my plaster bedroom wall and it was a very simple operation.
Locate the studs, using the mount body and the level as a guide mark where your screws will go with a pencil. Drill pilot holes and then you can mount the bracket with the included hardware. The feeling of a drill hitting a stud is extremely different than pushing through plaster/lath. If you have a second set of hands to hold things in place that can help a lot.
The only thing I could foresee being an issue about plaster is that if it is so compromised that the mount won't sit flush because of major gaps in the plaster behind it, but that would require a serious level of decaying plaster.
posted by Ferreous at 9:12 AM on March 31, 2022 [2 favorites]
Locate the studs, using the mount body and the level as a guide mark where your screws will go with a pencil. Drill pilot holes and then you can mount the bracket with the included hardware. The feeling of a drill hitting a stud is extremely different than pushing through plaster/lath. If you have a second set of hands to hold things in place that can help a lot.
The only thing I could foresee being an issue about plaster is that if it is so compromised that the mount won't sit flush because of major gaps in the plaster behind it, but that would require a serious level of decaying plaster.
posted by Ferreous at 9:12 AM on March 31, 2022 [2 favorites]
Best answer: There's little question you'll be able to successfully mount the TV.
The question is how much wall damage are you willing to accept in the worst case? Vibrations from screwing/drilling or accidentally catching the screw on a piece of lath and pulling it slightly loose, could crack and loosen the plaster up to a couple feet in all directions, possibly knocking big chunks out. You can just caulk these cracks and put up new plaster patch if chunks came out, and if it's behind a TV this will be easy so long as you don't care about the aesthetics of an imperfect wall. If you want the wall to be fixed nicely, you'd need to get a plasterer in to patch a big chunk of wall, which is a regular thing they do. All this is only if you have wood lath; if you have rock lath or something else, you're unlikely to cause anything but localized damage.
posted by flimflam at 9:30 AM on March 31, 2022 [2 favorites]
The question is how much wall damage are you willing to accept in the worst case? Vibrations from screwing/drilling or accidentally catching the screw on a piece of lath and pulling it slightly loose, could crack and loosen the plaster up to a couple feet in all directions, possibly knocking big chunks out. You can just caulk these cracks and put up new plaster patch if chunks came out, and if it's behind a TV this will be easy so long as you don't care about the aesthetics of an imperfect wall. If you want the wall to be fixed nicely, you'd need to get a plasterer in to patch a big chunk of wall, which is a regular thing they do. All this is only if you have wood lath; if you have rock lath or something else, you're unlikely to cause anything but localized damage.
posted by flimflam at 9:30 AM on March 31, 2022 [2 favorites]
You won't be attaching it to the plaster or even the lath behind it. You or your pro will be using wall anchors. They've got wings that spread after the last layer. The wings disperse the mounted item's weight. Wall anchors allow you to mount your item (TV, large and heavy picture, large mirror, large sculpture) regardless of the studs. Museums and galleries have their art all over their walls regardless of stud locations. The TV mount has four attachment points and those points might be wider or narrower than your house's stud widths. You or your pro might use toggle bolts for the safest and securest attachment. I might use toggle bolts regardless of the wall anchors sold with the TV wall mount kit. Many of the products have videos depicting their use and what's happening inside the wall. Attaching a TV mount to the wall is a project that you can handle. You've got this!
Unless it's a small, 4"x4" picture, I wouldn't hang anything to the wall without wall anchors. That's a pro tip for both drywall and plaster walls.
posted by dlwr300 at 10:31 AM on March 31, 2022 [1 favorite]
Unless it's a small, 4"x4" picture, I wouldn't hang anything to the wall without wall anchors. That's a pro tip for both drywall and plaster walls.
posted by dlwr300 at 10:31 AM on March 31, 2022 [1 favorite]
I completely disagree with dlwr300, you should never use wall anchors for heavy things, and especially not with lath and plaster walls -- that's just begging for the entire wall to fall down.
Anchor into the studs, as the previous posters mention. Wall mounts are made with lots of holes horizontally, so you can screw into a stud even with weird spacing.
posted by flimflam at 12:55 PM on March 31, 2022 [12 favorites]
Anchor into the studs, as the previous posters mention. Wall mounts are made with lots of holes horizontally, so you can screw into a stud even with weird spacing.
posted by flimflam at 12:55 PM on March 31, 2022 [12 favorites]
Best answer: The TV mount has four attachment points and those points might be wider or narrower than your house's stud widths.
The way I mounted a slightly heavier TV than yours on my elderly plaster wall was to attach a plate of half inch thick plywood spanning three studs using nine countersunk wood screws, three into each stud. Before mounting the plywood plate to the wall, I'd drilled holes in it to match the TV mount and hammered some quarter inch tee nuts into those on the back of the plate. After the plate was up, I screwed the TV mount onto it using half inch long, quarter inch mushroom head bolts that engaged with the tee nuts.
Having the plywood plate span three studs gave me the ability to position the TV mount exactly where I wanted it. It's not centred on the plate, and none of its own mounting holes have ended up anywhere near any of my studs.
I used a stud finder to get the approximate location of the studs, then drilled a horizontal row of 1/16" holes, quarter of an inch apart, until I'd found stud-free plaster on both sides of them. The plywood plate's mounting screws went in half way between those limits, so they ended up square in the centres of the studs. My house is old, the stud spacing is a bit weird, and as it turned out one of the studs I was using wasn't quite vertical, so I'm glad I did it that way.
You can't see the plywood without sticking your head around the back of the TV, and that TV is not coming off that wall until I take it off. No way, no how.
posted by flabdablet at 1:15 PM on March 31, 2022 [1 favorite]
The way I mounted a slightly heavier TV than yours on my elderly plaster wall was to attach a plate of half inch thick plywood spanning three studs using nine countersunk wood screws, three into each stud. Before mounting the plywood plate to the wall, I'd drilled holes in it to match the TV mount and hammered some quarter inch tee nuts into those on the back of the plate. After the plate was up, I screwed the TV mount onto it using half inch long, quarter inch mushroom head bolts that engaged with the tee nuts.
Having the plywood plate span three studs gave me the ability to position the TV mount exactly where I wanted it. It's not centred on the plate, and none of its own mounting holes have ended up anywhere near any of my studs.
I used a stud finder to get the approximate location of the studs, then drilled a horizontal row of 1/16" holes, quarter of an inch apart, until I'd found stud-free plaster on both sides of them. The plywood plate's mounting screws went in half way between those limits, so they ended up square in the centres of the studs. My house is old, the stud spacing is a bit weird, and as it turned out one of the studs I was using wasn't quite vertical, so I'm glad I did it that way.
You can't see the plywood without sticking your head around the back of the TV, and that TV is not coming off that wall until I take it off. No way, no how.
posted by flabdablet at 1:15 PM on March 31, 2022 [1 favorite]
And yeah, I would not ever mount something weighing forty pounds to a plaster wall with toggle bolts. Plaster is not a structural material, despite frequently being treated as if it were by people with much higher risk tolerance than mine. Studs or gtfo.
posted by flabdablet at 1:25 PM on March 31, 2022 [1 favorite]
posted by flabdablet at 1:25 PM on March 31, 2022 [1 favorite]
As for doing it yourself: I recommend copious pencil marks, a cardboard template to work out what size the plywood plate will need to be, a spirit level, and masking tape for sticking the template to the wall while you drill holes through it into your studs.
After making a few exploratory holes in the bare plaster wall to find the studs to begin with, I cut my template to suit and taped it to the wall and levelled it before drilling the rest of the stud mounting holes straight through it. That made it very easy to cut the plywood plate to size and then transfer the stud mounting hole locations onto it. It also let me use the TV mount as a stencil to mark its own hole locations, and check that it was going to end up in the right place before I'd even cut the plywood.
I left two inches between the edges of the template/plywood and the outermost screw holes.
posted by flabdablet at 1:41 PM on March 31, 2022 [1 favorite]
After making a few exploratory holes in the bare plaster wall to find the studs to begin with, I cut my template to suit and taped it to the wall and levelled it before drilling the rest of the stud mounting holes straight through it. That made it very easy to cut the plywood plate to size and then transfer the stud mounting hole locations onto it. It also let me use the TV mount as a stencil to mark its own hole locations, and check that it was going to end up in the right place before I'd even cut the plywood.
I left two inches between the edges of the template/plywood and the outermost screw holes.
posted by flabdablet at 1:41 PM on March 31, 2022 [1 favorite]
the plaster is crumbly enough that mounting a curtain rod left little holes around the bracket.
Plaster will crumble if you bang anything but the thinnest of thin nails into it, or if you try to screw stuff in using screws with shanks that are thicker than the holes through the plaster. Modern drywall can hide that to some extent because of its paper facings, but old-school solid plaster won't.
When you're drilling a pilot hole into a stud for a wood screw, use a drill bit that's smaller than the thickness of the wood screw's threads, so that the threads will bite properly into the wood. Then widen out only the part of that hole that's going through the plaster, using another drill bit that's a smidge thicker than the thickest part of the wood screw's shank. That way the screw won't be trying to displace plaster as it goes in, and the plaster won't crumble.
Pick screws that are long enough to penetrate at least two inches into the stud after allowing for the thickness of the plaster plus whatever you're screwing onto the wall. I used three inch screws, allowing half an inch for plywood plus another half inch for plaster.
When drilling holes through plaster, I always like to have the vacuum cleaner running and the tip of its crevice tool right underneath the point where the drill bit is going in. That way, plaster dust ends up going straight into the vacuum bag instead of down the wall and on the floor and in the air.
Also, I just went and looked at that TV mount again and it turns out I lied about there being nine screws into the studs. It looks like I only used six, two into each stud. But they're pretty chonky batten screws, so there's no way they're ever letting go.
posted by flabdablet at 2:25 PM on March 31, 2022 [1 favorite]
Plaster will crumble if you bang anything but the thinnest of thin nails into it, or if you try to screw stuff in using screws with shanks that are thicker than the holes through the plaster. Modern drywall can hide that to some extent because of its paper facings, but old-school solid plaster won't.
When you're drilling a pilot hole into a stud for a wood screw, use a drill bit that's smaller than the thickness of the wood screw's threads, so that the threads will bite properly into the wood. Then widen out only the part of that hole that's going through the plaster, using another drill bit that's a smidge thicker than the thickest part of the wood screw's shank. That way the screw won't be trying to displace plaster as it goes in, and the plaster won't crumble.
Pick screws that are long enough to penetrate at least two inches into the stud after allowing for the thickness of the plaster plus whatever you're screwing onto the wall. I used three inch screws, allowing half an inch for plywood plus another half inch for plaster.
When drilling holes through plaster, I always like to have the vacuum cleaner running and the tip of its crevice tool right underneath the point where the drill bit is going in. That way, plaster dust ends up going straight into the vacuum bag instead of down the wall and on the floor and in the air.
Also, I just went and looked at that TV mount again and it turns out I lied about there being nine screws into the studs. It looks like I only used six, two into each stud. But they're pretty chonky batten screws, so there's no way they're ever letting go.
posted by flabdablet at 2:25 PM on March 31, 2022 [1 favorite]
Best answer: You can definitely do this. Don't try and mount to anything but the studs, though!
A stud-finder is your best best for finding the studs and, once you've found them, you just need to align the holes in the bracket (the part that fixes to the wall) with those studs. You generally have a lot of latitude and the bracket doesn't have to be centred on where the TV is going (within reason). Just fix into the stud with at least four screws and, once you've fixed the other half of the bracket to the TV, you're ready to hang the TV.
Before you start, though, think about all those cables and how you're going to get them to the TV from wherever. You don't want a beautiful clean wall-hung TV marred by a bunch of cables dangling down the wall. It's not difficult to run them down the wall, as long as there's not a noggin in the way - just cut or drill a hole behind the TV and one behind your entertainment unit or wherever any connected boxes are. It's much simpler if you don't have any such boxes, of course and, in that case, all you need to do is run the power and antenna cables up inside the wall.
posted by dg at 4:31 PM on March 31, 2022 [1 favorite]
A stud-finder is your best best for finding the studs and, once you've found them, you just need to align the holes in the bracket (the part that fixes to the wall) with those studs. You generally have a lot of latitude and the bracket doesn't have to be centred on where the TV is going (within reason). Just fix into the stud with at least four screws and, once you've fixed the other half of the bracket to the TV, you're ready to hang the TV.
Before you start, though, think about all those cables and how you're going to get them to the TV from wherever. You don't want a beautiful clean wall-hung TV marred by a bunch of cables dangling down the wall. It's not difficult to run them down the wall, as long as there's not a noggin in the way - just cut or drill a hole behind the TV and one behind your entertainment unit or wherever any connected boxes are. It's much simpler if you don't have any such boxes, of course and, in that case, all you need to do is run the power and antenna cables up inside the wall.
posted by dg at 4:31 PM on March 31, 2022 [1 favorite]
Best answer: This is just my personal opinion but when hanging something like a TV or a grab bar, I never trust stud finders or magnets and I don't assume anything is accurately on 16” centres . I take my smallest drill bit and make a series of tiny holes to clearly feel where the edges of the studs are, so that I know I'm drilling dead in the centre for my mounting holes. The exploratory holes are easy to poly-fill and probably won’t be noticeable if your walls are a light colour. Take a second to note where your electrical outlet is. You’ll want to avoid doing a ton of exploratory drilling directly above it.
Also just my personal opinion but if I'm using big #10 lag bolts, I pre-drill a hole that's the same size as the diameter of the screw, minus the threads. To help them go in easier, I give them a single rub with a bar of soap.
posted by brachiopod at 7:50 PM on March 31, 2022 [3 favorites]
Also just my personal opinion but if I'm using big #10 lag bolts, I pre-drill a hole that's the same size as the diameter of the screw, minus the threads. To help them go in easier, I give them a single rub with a bar of soap.
posted by brachiopod at 7:50 PM on March 31, 2022 [3 favorites]
I wouldn't. Not for a heavy TV.
Plaster is a cosmetic material, not a structural material. It's brittle as hell, and if you overload it even briefly it will fail suddenly and completely. These are not properties compatible with safety when mounting a heavy television, especially high up.
If you try to increase a plasterboard mount's load rating - especially a heavy duty one - by spreading the load across multiple mounts, all you're doing is putting way way way more stress on the bulk of the plaster itself and its mounting screws than you can reasonably expect them to deal with.
For heavy loads on plastered walls, I don't care what the wall mount manufacturers claim they can do. For me it will always be studs or gtfo.
posted by flabdablet at 9:50 AM on June 30, 2022
Plaster is a cosmetic material, not a structural material. It's brittle as hell, and if you overload it even briefly it will fail suddenly and completely. These are not properties compatible with safety when mounting a heavy television, especially high up.
If you try to increase a plasterboard mount's load rating - especially a heavy duty one - by spreading the load across multiple mounts, all you're doing is putting way way way more stress on the bulk of the plaster itself and its mounting screws than you can reasonably expect them to deal with.
For heavy loads on plastered walls, I don't care what the wall mount manufacturers claim they can do. For me it will always be studs or gtfo.
posted by flabdablet at 9:50 AM on June 30, 2022
Nope, don't use any form of anchor into plasterboard to secure anything that can't survive a sudden drop to the floor. The alleged weight capacity of such fasteners is derived from very specific circumstances that will not match the weight of a TV spaced out from the wall by a bracket at all. They also don't take into account the weight capacity of the plasterboard itself, which is more or less nil. Adding more anchors will not increase the capacity and will only mean more holes to repair when the TV inevitably crashes to the floor.
posted by dg at 8:25 PM on June 30, 2022 [1 favorite]
posted by dg at 8:25 PM on June 30, 2022 [1 favorite]
This thread is closed to new comments.
posted by Ferreous at 8:55 AM on March 31, 2022 [5 favorites]