Tv mount - metal studs

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Old 05-28-14, 03:21 PM
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Tv mount - metal studs

I've mounted 1 TV in my place which has metal studs, which are new to me. I also hung kitchen cabinets using the same technique, which was to open the wall and put 2x8's in between (and screwed into) the metal studs and mount onto that.

Now I am mounting a smaller tv- 32". It will have an articulating mount. I want to try the technique of using 3/4 plywood into the studs and the mount onto that to save me a big hole that needs to be patched.

I have seen toggle bolts for metal studs and drywall that claim to hold all kinds of weight. The problem is, My studs are only like 2.5" deep. All these high weight toggles seem to require more depth than that.

I guess I can use drywall type screws to fasten the plywood to the studs. Any other ideas?

The mount will use lag bolts into the plywood.
 
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Old 05-28-14, 03:25 PM
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I think you are on target by using the plywood to span across the studs. You would use a fine thread, self tapping metal stud screw to penetrate the metal and hold. I would think a few in line on each stud should hold sufficiently. Putting a toggle bolt in the middle of the stud bay won't hurt, either.
 
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Old 05-29-14, 05:22 AM
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I would use three stud screws into each stud, closely spaced near the top edge of the plywood panel. And a fourth near the bottom edge.

I don't think any fastening into the wall in the middle of the stud bay is going to add much more holding power. That fastening is relying only on drywall.
 
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Old 05-29-14, 12:26 PM
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The problem with what you want to do is that when you put the brace in front of a metal stud, there is only a tiny point of contact at the thread of each screw. When you run the 2x8 BEHIND the stud, the surface area of the bite is exponentially bigger, because the screw head is spreading the load over a larger area of the metal - just like a washer.

If you want to do a front-brace, first of all I would use 1" lumber. Plywood is not designed with that kind of force resistance in mind. Second, you can install a Toggler fastener with as little as 1" behind the surface.

If this is a 'single stud' mount, I'm not sure I'd trust a metal stud not to deform by itself.. But if you were to just use a piece of 1" oak or something as a backer, you could run the Togglers into the stud, then bolt the mount through the backer into them and it would be fine.

If it's a two-stud mount, then fasten the bridge piece using four of the Togglers, with the bridge overlapping each stud by at least an inch.

 
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Old 05-29-14, 12:44 PM
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I was looking to use one of those type of togglers. When I look online (like homedepot.com), then all take 2.5 screws they say. My stud perfectly holds a 2xwhatever which means I have 1 3/4". If I use plywood or wood of 3/4" or 1", I guess that, combined with the drywall thickness would give me 2 1/2".
 
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Old 05-29-14, 06:15 PM
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They don't come with screws. You use a 1/4"-20 bolt in whatever length you need.
 
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Old 05-29-14, 06:42 PM
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First post but longtime installer. The zip toggle pictured above is all you need. I wouldn't even bother trying to hit a stud. You can get them in 3/16 as well if your mount holes are smaller. I have used them in as low as 3/8 drywall with 1" screws with no problem. I have mounted TVs up to 60" without touching studs. These toggles are excellent. If your local Depot doesn't carry them, try Fastenal.
 
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Old 05-30-14, 02:41 AM
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AllanJ makes a good point regarding sheetrock only attachment. We are talking about an articulating mount, not just shear, but lateral pull. Sheetrock only won't take it, IMO.
 
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Old 05-30-14, 03:06 AM
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My company recently installed 350 26-inch televisions on articulating mounts in a hospital. Each mount had a wall plate that was about 7 inches high by 3 wide. We used two of those Togglers in each. We tested the first few by hanging from the mount with the 15-inch arm fully extended. Didn't budge. Not one of the 350+ has failed.

Four Togglers holding a piece of plywood is plenty, but the plywood may not be necessary. Just use the Togglers to hold the mount. The 1/4-20 bolt only has to be long enough to penetrate the drywall and land in the threads. 1 1/2" should be plenty.
 
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Old 05-30-14, 09:43 AM
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It is funny how many different opinions there are on mounting with metal studs. I've searched and read 100s of posts. Obviously, I prefer to err on the side of overbuilding rather than under.

I don't particularly want to open the wall to reinforce because it is an outside wall and you have to contend with removing insulation.

Wood over the drywall I think is okay, but with an articulating mount you will see it.

Since I am using a 32" tv, I think I will use toggles. 2 toggles into 2 studs and maybe 2 toggle into the drywall in between. I can't imagine that not being enough.
 
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Old 05-30-14, 12:00 PM
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If I worked for some huge corporation like MasTec where bean counters and profit margins dictate policy instead of people who have common sense, and their written policy is to to hang an articulating TV mount on drywall alone, I'd do it because it's not my problem if it falls.

However, being as I am the face of my own company, and it's my livelihood and insurance policy on the line when I do an installation, I ALWAYS favor the side of caution and overengineer when it comes to hanging displays. I would NEVER trust drywall alone to hold the weight of an articulating mount, even if the Toggler package claims it will. The bolt itself won't pull out, but there's nothing to stop the whole Toggler from ripping right through the drywall. With articulating mounts, the force is lateral (that is, it's pulling OUTWARD on the drywall) - and that is exacerbated by the fact that the Toggler will bite through the drywall's backing paper as you tighten it, versus shearing (pulling DOWNWARD). The drywall can withstand many times more weight in shear force than it can with lateral force.

And that is why I say to make SURE the Toggler hits the face of the stud, because that is reinforcing the lateral plane so it can't just pull right through. Having the wood in FRONT of the drywall stiffens the mounting surface - because drywall is flexible and so is the thin sheet metal behind it. It could end up bowing out on you and cracking the drywall if the TV is heavy enough.
 
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Old 05-30-14, 03:24 PM
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I've been hanging articulating mounts for as long as they have existed the same way always. It's got nothing to do with profit margins or bean counting it just simply works. Zip toggles and drywall will hold it fine, but it's your mount, do what you want. Only ever had one failure on a wall mounted bookshelf and that's because an HVAC tech stood on it. It held him for a half hour before it let go. If you need to over-engineer something as simple as a TV mount, you are overcharging your customer for both materials and labor.
 
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Old 05-30-14, 06:28 PM
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Just because one's stupidity/laziness hasn't bitten them in the ass yet doesn't mean stupid/lazy is the right way to do it. Nor is it any basis for advising others to follow said stupid/lazy example. That's like telling someone that it's OK to use Scotch tape on electrical connections because you've been doing it since the invention of Scotch tape and only one person has been zapped as a result.

Bottom line is your suggestion is dangerous, and it is a liability, and nobody should follow it.
 
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Old 05-30-14, 10:10 PM
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I guess I am not sure why you wouldn't use a stud if it is there (whether metal or wood). Since all walls have them, why not use it?
 
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Old 05-30-14, 10:38 PM
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My point exactly. There is absolutely NO valid reason. He's playing with fire and eventually he's going to get burned. Some sugared up 8 year old is going to decide to use the arm of one of his idiotic drywall only mounts as a chin up bar, and it is going to come crashing down.

If it's your own mount, you do whatever you want because you are responsible for what's going to happen with it. But when you install things for other people, you automatically HAVE to assume that they are going to do something absolutely idiotic with it and then try to sue you when they get hurt.
 
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Old 05-31-14, 04:16 AM
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Please, let's keep it civil, guys.

The hospital installation sometimes hit studs, sometimes didn't. Their electric and carpentry shops have been using Togglers for years without incident. They both approved our use of them.

Divide the length of the cantilever by the height of the base and multiply the result by the intended weight to get the tension on the top fastener. With our rigs that worked out to about 35 pounds fully extended. Each toggler into 1/2" drywall is rated at 265 lbs tensile -- a safety factor of more than 7 to 1 for each fastener.

However, the hospital had 5/8" drywall, which has roughly 30% more tensile strength than the 1/2" that's typically used in homes. Our safety factor was actually just over my self-imposed design minimum of 10:1. For each fastener.

michaeljc70, which mount and TV will you be installing? Post makes & models and let's do the math.
 
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Old 05-31-14, 12:50 PM
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You're talking apples to oranges, Rick. In a hospital, the TV's are up high, out of reach of any children (and most adults ), and they are for all intents and purposes never going to be moved again once they are aimed. In a home environment, it is going to be 40" off the floor, and it will probably be moved regularly. Every time it's moved/jarred/pushed/pulled weakens the drywall a little more.

Now as far as the listed load ratings, first of all you have to use the 'working load' ratings, not the 'ultimate load' ratings. The 'ultimate load' rating is like the 'peak power rating' on a speaker or amplifier - it means nothing. The 'working load' ratings of these fasteners is 1/4 of the 'ultimate load'. So the working tensile load of the 265lb rated fastener is 67lbs (which drops your safety margin for a 35lb calculation below 2:1).

And to get that 'ultimate' rating, basically they attached a force gauge to a hydraulic ram and pulled slowly and smoothly on a fastener till it blew through the surface. The listed load rating is an average of whatever number of tries they did with each fastener/surface. In a common articulating mount application, the load is hardly going to be a smooth constant pull like that. Another consideration is that their tests were done using brand new drywall. As drywall ages it gets brittle. Moisture can weaken it (a huge factor in a basement install). The paper backing is all that gives the fastener its strength. If the wing bites into the paper because the bolt was tightened 1/2 turn too much, the integrity is compromised.

It's stupid no matter how you slice it.
 
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Old 05-31-14, 01:23 PM
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I am using the Cheetah Mounts APDAM3B Dual Articulating Arm mount. I can't find an exact weight on that. The tv is 39" and weighs 13lb (it is between 2 windows and I can't go much larger than 39").

The drywall is 5/8. The studs I am not sure of the size. That is an exterior wall, and I think they used standard 2x4 studs. My interior walls use smaller studs that are only 1.5" deep (it is a townhouse and support is cement block with trusses on connecting walls).
 
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Old 05-31-14, 02:45 PM
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Following the formula that Rick posted, that mount has a 14" extension, plus we'll call it 4" for the depth of the TV+VESA mount at the end of the arm. So 18". And the back plate is 6" tall. So divide 18 by 6 and that's three. The TV weighs 13lbs, and the mount weighs 12lbs. So 25x3=75lbs on a single top fastener.. A Toggler's working load in 5/8" drywall is 89lbs. Two fasteners only gives you a 2:1 safety margin.

Simply having the two Togglers through a 25ga stud along with the 5/8" drywall increases that to a 240lb capacity (3:1) - and you need to consider that the metal stud 'ultimate load' ratings are the point when damage started to appear on the drywall from the flex, NOT when the wing actually ripped through the metal stud. Adding a strip of hardwood lumber over each stud (or using a full-span bridge piece) will keep the area from flexing and further increase the weight that can be carried before damage occurs. The "drywall only" ratings are when the wing actually ripped through.

And also remember, you divide the total load among the TOP fasteners only. They bear all of the pulling force. The bottom fasteners bear virtually no load so they do not factor in.
 
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Old 06-01-14, 05:14 AM
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A working load rating is exactly that: The amount of weight the product is designed to hold. It already has the 4:1 industry recommended safety factor built in. Here is the textbook wording: "The maximum tensile stress should be less than or equal to ultimate tensile stress divided by factor of safety."

The industry standards recommend 1/4 of the ultimate test load to give it a built-in safety factor of 4:1. It's the same thing that we're doing by calculating the load and deciding how much we want to have as a safety factor. I personally like to design with 10:1 whenever possible, but 4:1 is the industry standard. You have more than 5:1 with your rig, michaeljc70.
 
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Old 06-01-14, 10:36 AM
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I think we have been given different data as in post #18, indicating all the arguing was about nothing. OP has standard framing on an exterior wall, so the playing field changed dramatically.
 
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Old 06-01-14, 10:39 AM
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I think we have been given different data as in post #18, indicating all the arguing was about nothing. OP has standard framing on an exterior wall, so the playing field changed dramatically.
Standard size, but still metal. I don't think that matters though. It is the thickness of the front of the stud that would matter - not the dead space behind that.
 
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Old 06-01-14, 10:43 AM
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OK, so "standard METAL studs", not standard studs. SO we can get back to arguing again. I'm just observing.
 
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Old 06-01-14, 04:04 PM
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I've been following this only because I have no experience with metal studs.

I don't doubt Rick's numbers or experience. But experience has also taught me that
erroring on the side of caution might cost a bit more but it never hurts. I think Jersey has made the case that liabilty is the key component in this senario. One failure and one injury is all that is needed, even if the install was not directly at fault.
 
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