[W. K. Lis]

Apparently you should be able to mount the TV on metal studded walls. See this link. Basically, you should use more toggle bolts. Buy more toggle bolts to spread the load if they don't supply enough bolts with the wall mount.

For a 47" 56lbs LCD TV:

spanning across all 3 metal studs...

I will then place 2 toggle bolts into each metal stud and then 2 toggle bolts into the drywall between each stud, making for a total of 10 toggle bolts. 6 going into the metal studs, and 4 going into the drywall.

There is also this video, for TV that weigh up to 80 lbs.:

[video=youtube;C9l0zkd91oM]http://www.youtube.com/watch?v=C9l0zkd91oM[/video]

 

[Eug]

I'm no engineer, but if I had to do it, I'd cut out a piece of 3/4" plywood, and then use toggle bolts to mount the plywood to preferably 3 but at least two metal studs, with several toggle bolts per stud. Then I would screw the TV mount into the plywood. This is assuming the drywall is directly mounted on the metal studs (which isn't always the case).

However, doing it the way as described in the thread that W. K. Lis linked above is also an option, with the mount directly toggle bolted into the studs.

It's interesting they mention the Monoprice mounts though since they're less sturdy to begin with, and there may be some flex in the metal.

While it is possible to mount only into drywall as described in that video, it's pretty unsafe in my opinion. If you never ever move the TV, then it may be OK, but many mounts have tilt (up/down and/or sideways), and a few even extend from the wall somewhat. Those mounts put a lot of leverage on the mount points, and that can cause the mount points to rip through the drywall. And if not through, then a little bit through, which will loosen the mount points. I certainly wouldn't use plastic drywall anchors either. Toggle bolts through drywall are definitely better, but still not ideal. Drywall is simply inherently weak. It also depends on the TV. Obviously an uber thin 32" LED is going to be a lot lighter than a 50" plasma.

Meanwhile, I did the framing in my basement in wood. I knew where the TV was going to be, so I just made sure the framing was re-inforced in the appropriate spots, with horizontal braces. Sooo much easier... Even non-re-inforced 2x4 studs are more than fine.

By the way, I just had to deal with something similar at my mom's place. Her closet's shelving with integrated clothes' hangar bar was mounted into the drywall. It looked prefectly fine, until my mom started hanging her heavy clothes onto it, and putting some boxes on the shelf. The drywall anchors all ripped right through. So, I drilled holes into the cement in behind and screwed fasteners directly into the cement. Much more sturdy. Toggle bolts in this instance wouldn't work anyway. There was a small space between the cement and the drywall, but there were no metal studs in that spot. So I suspect the drywall was mounted onto shallow metal rails which were in turn mounted on the cement. Toggle bolts wouldn't work because there wasn't enough space to insert them. You'd hit the cement before the entire wings of the toggle bolts went through, so the wings (or whatever they're called) wouldn't open up. This was a wall between two units, and I'm guessing many condos are built this way for common walls between units. It's the interior walls that more consistently have the metal studs.

 

[Wooba]

Toggle bolts are not designed to be used with a stud. They would be a nightmare to install (although granted, they'd be strong). Regular screws (something that bites like a drywall screw) would be more than enough for what Eug is describing.
If I was doing it myself I would cut the drywall in a rectangle larger than the bracket and then install plywood within the wall securing the studs. It's a bit of a hassle to fix with the mud and paint, but sometimes the better way takes a bit more effort.

I mounted a TV at my old place and installed plywood in the wall, but I had the luxury of going there before the drywall was installed. I used a monoprice mount and it was built like a tank so I'm not sure what Eug means about them being less sturdy.

 

[Eug]

Toggle bolts are not designed to be used with a stud. They would be a nightmare to install (although granted, they'd be strong). Regular screws (something that bites like a drywall screw) would be more than enough for what Eug is describing.

You use a proper drill bit to drill a hole through the metal, and then insert the toggle bolts. You could use metal screws to do this, but toggle bolts would be stronger. I would not trust drywall screws, because they are not meant to carry a significant load.

I have a Monoprice mount for one TV. They are great for the price, but less well designed and less sturdy than some of the higher end mounts out there. However, the ones I'm talking about cost 5X as much.

 

[James]

The main precaution to take with toggle bolts is that while they are very strong in pullout, the limiting factor is typically the partition in which they are fastened through. Although the specs on toggle bolts through a single layer of drywall are pretty impressive, I would not recommend using them alone for supporting a TV. A drywall/metal stud frame assembly would be more than adequate with proper anchor bolts. Adding in a plywood backing will definitely add more stability to the installation but not absolutely required. Also, one should be careful not to add too many fasteners to any mounting surface, regardless what you're installing, as that can weaken the entire assembly. More bolts is not always better.

 

[W. K. Lis]

If you ever wall mounted shelving, you would discover that the weight of the books can get very heavy. If they can hold up a set of encyclopedias, magazine collection, book collections, or an aquarium on them, a TV would be fine.

 

[Eug]

If you ever wall mounted shelving, you would discover that the weight of the books can get very heavy. If they can hold up a set of encyclopedias, magazine collection, book collections, or an aquarium on them, a TV would be fine.

I came back to my office after a vacation to find my office bookshelf was leaning over my desk, because the top mounts had ripped themselves out of the drywall. This was after about a year.

For some reason the contractors hadn't bothered trying to mount the shelves on the studs. The whole thing had to be taken down, and then remounted on the studs.

Plus TV mounts are not the same as bookshelves anyway. Bookshelves are generally flush mounted to the wall, with the books near the wall, and no vertical or lateral movement of the shelves. In contrast, some TV mounts extend outward to a certain extent, to accommodate different viewing angles by tilting, and the heavy TV is at the end of this lever. Furthermore, often times with a TV mount, the mounting area is comparatively small compared to many bookshelves. This, along with the repeated movement caused by tilting, can cause some serious strain on the mount points that a bookshelf may never see.

 

[James]

I came back to my office after a vacation to find my office bookshelf was leaning over my desk, because the top mounts had ripped themselves out of the drywall. This was after about a year.

For some reason the contractors hadn't bothered trying to mount the shelves on the studs. The whole thing had to be taken down, and then remounted on the studs.

Plus TV mounts are not the same as bookshelves anyway. Bookshelves are generally flush mounted to the wall, with the books near the wall, and no vertical or lateral movement of the shelves. In contrast, some TV mounts extend outward to a certain extent, to accommodate different viewing angles by tilting, and the heavy TV is at the end of this lever. Furthermore, often times with a TV mount, the mounting area is comparatively small compared to many bookshelves. This, along with the repeated movement caused by tilting, can cause some serious strain on the mount points that a bookshelf may never see.

That is, by far, the most common and anticipated mode of failure when it comes to bookshelves. If the weight of all the books were directly applied right at the shelf/wall interface, the total number of bolts would each be subject to a fairly uniform shear stress. Once the weight shifts away from the wall, as in the case of an adjustable flat panel TV and (to a lesser degree) books, the stress becomes bending and pullout vs. strictly shearing. The pullout forces the bracket to want to "peel off" from the top first down to the bottom. The top anchors are much more critical than the lower anchors.

In the photo example above, most of the load is going to be pullout along the top of that bracket. Technically, if you have a large enough metal bracket (it only has to be wide enough to accommodate the required number of properly-spaced fasteners and it has to extend low enough to resist the bending moment due to the TV being cantilevered out so far), you only need the appropriate number of fasteners along the top to secure it in place permanently.

Lastly, as I think Eug has mentioned, one of the biggest issues (and unknowns) is not with the static weight of the TV but rather with people constantly moving, pulling, twisting and turning the mounting arm, which essentially just transfers all those loads to the bracket/fasteners and, consequently, to the drywall/stud assembly.

 

[Wooba]

You use a proper drill bit to drill a hole through the metal, and then insert the toggle bolts. You could use metal screws to do this, but toggle bolts would be stronger. I would not trust drywall screws, because they are not meant to carry a significant load.

I think you grossly under estimate the strength of drywall screws. Holding heavy stuff on studs is what they are designed to do. There are quite literately billions of sheets of drywall on walls and ceilings around the world that are often as heavy or heavier than a TV and are able to stay in position just fine. Even when saturated with water from a flood they are able to handle the load without problem. Using an 8 screw configuration as you showed in your picture for toggle bolts would be rock solid. Try what you suggested with drywall screws, put some handles on it and I bet you and 4 of your strongest friends wouldn't be able to pull it off.

I've installed thousands of toggle bolts in my career and until your posting I've never heard of or seen anyone using toggle bolts through a stud, nor have I seen it on any fixture I've removed. They are designed for use on drywall. There's no question if you're willing to take the time what you've suggested would work and would be very secure but it would be like using the heaviest gauge deep see fishing line to catch goldfish in your back garden pond. It's needlessly time consuming and complicated.

 

[Eug]

So I just googled this, and one of the first links I get is an eHow article:

http://www.ehow.com/how_4814406_install-plasma-tv-metal-studs.html

You can install your wall-mounted plasma TV into metal studs using toggle bolts. Toggle bolts will provide the strength necessary to hold your TV and maintain the integrity of the metal stud.

Another link is a This Old House article:

http://www.thisoldhouse.com/toh/asktoh/question/0,,1061866,00.html

Now for steel-stud framing, toggle bolts are the way to go.

---

Oh and with regards to the strength of drywall screws:

http://www.metacafe.com/watch/967794/shear_strength_of_nails_drywall_screws_construction_screw/

Conclusion is never to use drywall screws where strength matters.

 

[Wooba]

Regarding the toggle bolts, as I said I've never seen that used in the real world ever. Neither have any of my colleagues that I asked today. As I also said twice, it will work and will be strong but it's grossly over doing it IMO. We routinely mount sheets of plywood to which we then mount various pieces of equipment that are considerably heavier than any TV you can buy today. It has been done this way long before I got into the trade.

Regarding the video of the screws, a pointless demonstration. Since I won't be leaving the screws poking out and won't be hammering them with the TV it's hardly relevant. What's relevant is the application it's being used for and is it being applied correctly? I can take a piece of aluminium and bend it back and forth a few times to make it break in seconds. Yet that same substance is used to build aircraft that take people all around the globe. One screw correctly installed isn't going to snap the way he showed. Several of them are absolutely solid.
Also, his advice to use nails FOR FRAMING. He's not talking about mounting to a wall. Again this comes down to correct application. Using a drywall screw for framing would be idiotic.
Additionally, if someone who doesn't know the difference was to read your post and view the video might not realize that this applies only to wood. Using a nail in a metal stud would be practically guaranteeing failure.

 

[Eug]

Regarding the toggle bolts, as I said I've never seen that used in the real world ever. Neither have any of my colleagues that I asked today. As I also said twice, it will work and will be strong but it's grossly over doing it IMO. We routinely mount sheets of plywood to which we then mount various pieces of equipment that are considerably heavier than any TV you can buy today. It has been done this way long before I got into the trade.

Well, I agree that proper screws will work too, but I prefer stronger rather than weaker, and you agree toggle bolts will be stronger. And while you and your colleagues haven't used this method, clearly other people do. The first two construction advice articles that popped up when I searched this yesterday recommended this method.

Regarding the video of the screws, a pointless demonstration. Since I won't be leaving the screws poking out and won't be hammering them with the TV it's hardly relevant. What's relevant is the application it's being used for and is it being applied correctly?

Indeed. Shear strength is essentially what he is demonstrating. And the point here is that drywall screws have lousy shear strength. Quite honestly you are the first person I have ever heard of recommending drywall screws for this purpose. Every person I have ever dealt with would never use drywall screws for stuff like this, because drywall screws are inherently weak. They are not called construction screws, and should not be used as such. As you suggest, the right screws for the job, as it were.

I can take a piece of aluminium and bend it back and forth a few times to make it break in seconds. Yet that same substance is used to build aircraft that take people all around the globe. One screw correctly installed isn't going to snap the way he showed.

So, do you use aluminum screws? No? Why not?

Additionally, if someone who doesn't know the difference was to read your post and view the video might not realize that this applies only to wood. Using a nail in a metal stud would be practically guaranteeing failure.

Well, I would hope there would be at least some common sense involved. If you hammer a nail into a metal stud, you can often pull it out with your fingers, for obvious reasons.

 

[doug]

because drywall screws are inherently weak.

It's always interesting to read the 'facts' presented by non-professionals.

 

[W. K. Lis]

From this link:

Weight Support

The strength of the toggle bolt is determined by the length and diameter of its screw body. A 1/8-inch toggle screw, for example, is able to hold a 50-pound object on half-inch drywall. A 3/8-inch toggle is capable of supporting 100 pounds.


Read more: How Much Weight Can a Toggle Bolt Hold? | eHow.com http://www.ehow.com/facts_7508027_much-can-toggle-bolt-hold.html#ixzz23Xnei3En

Use washers at the screwhead to spread the load.

 

[Wooba]

Quite honestly you are the first person I have ever heard of recommending drywall screws for this purpose.

So what screws do you use to mount drywall then? If the answer is drywall screws then the question is, why would they be acceptable for drywall but not for plywood? They are similar in weight, size and thickness. If anything they will work better with plywood than drywall because it doesn't weaken if you over tighten the way drywall does.

So, do you use aluminum screws? No? Why not?

Of course I don't. If you read what I wrote I was demonstrating that using a product for the purpose for which is is not designed will give you poor results. In this case hitting half installed screws with a hammer breaking them does not accurately reflect how they do the job for which they are designed.

Well, I would hope there would be at least some common sense involved. If you hammer a nail into a metal stud, you can often pull it out with your fingers, for obvious reasons.

Obvious to you and me perhaps, but there's plenty of people who don't have any handyman type skills who will take advice like this as valid. I dare say many people reading this thread have never even heard of a toggle bolt, never mind what they are.