[Jeff-in-MN]

Hello-- I a 9'x9' steel pergola on my deck (pre-fab from Home Depot). The posts are 4"x4" hollow steel. It's pretty strong, but definitely sounds hollow if you hit your knuckles on it. I'm planning to mount a small (24") TV toward the top of one of the posts. The TV is about 7 pounds, and the mount is about 2.5 pounds (mounted with two vertical in-line screws/bolts). I'm looking for the best way to mount this so that it won't put too much strain on the column, won't rip out, etc. I expect that the steel is strong enough, but I'm wondering if I should get bolts that are long enough to go all the way through the post so that there's a nut on the other side of the opposite post wall (i.e., the bolt passes all the way through the post)? Or would one "wall" of the post with an anchor be strong enough to hold about 10 pounds of weight? I'm not familiar enough with shear force and construction to know if this whole plan is unwise. 10 pounds seems reasonable, and I know that the thickness/quality of the steel posts is definitely a factor. If this is possible, I'd just like to know the best option to safely mount this without screwing up the look/integrity of the pergola itself, while still ensuring that the TV will stay mounted. Is there a particular type of screw/bolt that would be best? I live in MN, so weather extremes are a factor. The TV itself can be easily removed from the mount, so it will either be covered or brought inside during storms, winter, etc.

Another option: Would adding a small piece of wood between the mount and the post be of any value? It's not great aesthetically, but if it's going to add integrity to the setup, I'd consider it.

Thanks,
Jeff

 

[Joeywhat]

How thick is the steel? Not in terms of overall width of the column, but the gauge of the steel wall. That will determine how you can mount it.

If the steel is thick enough you can thread a hole right into the steel and use some machine screws or bolts to attach. If it's too thin, I would use a toggle bolt or expanding anchor designed for thin materials (anchors designed for 1/2" or thicker drywall probably won't work). A toggle bolt will hold the weight just fine, even in thinner wall steel like what you might have.

If the material is VERY thin (i.e. gutter material) I would look at a through bolt setup, and use fender washers on the other side of it to spread out the load from the nut.

Adding wood won't help any, unless you can add the wood to the inside of the post.

If I were doing this, and I had no idea the wall thickness of the post, I would just use some toggle bolts and call it a day. I would prefer threading the post and using bolts as it'll be easier to mount in my opinion, but a toggle bolt will work for you unless the post is very thin.

 

[Jeff-in-MN]

Thanks; I looked up the specs on the HD site, and I can't find any mention of the gauge of the steel. My best guess is about 1/16" (16 or 18-gauge, maybe?). It's definitely thicker than gutter material. The 4 posts are holding up the weight of a top structure with a retractable canopy, so they are fairly substantial. I've had it outside year-round in MN for 2 years, with no bending/bowing. It looks like this (I can't get pictures to post today for some reason).

I'd say that it's probably not thick enough to thread into it, but using a toggle bolt should be sufficient. I'm assuming I'll be OK to just go through one face of the post (instead of going all the way through to the other side). If it looks like it's bending or straining the steel, I'll remount it with something long enough to go all the way through the post.

Thanks
Jeff

 

[Joeywhat]

Definitely not enough to thread. You only need to go through one side, keep the toggle internal so it looks better. You won't gain any strength going all the way through with such a light load.

 

[huesmann]

Do you have pics of your mount?

 

[Jeff-in-MN]

Do you have pics of your mount?

Probably something like this. A simple 2-screw mount with a moving arm. I've mounted other TVs with this setup. It should be more than capable for a 7.5-lb TV (assuming the post is up to it).

I found some anchors that I think will work well for this application (WingIts).

Sorry--Pictures are still not showing up as anything other than placeholders in my posts, so I inserted links instead.

--Jeff

 

[huesmann]

(If you click the little yellow square with the mountains above, next to the globe with the chain, you can insert a link to a photo.)

Do you think the steel of your posts can handle that weight? I guess the good thing is, if not, you can always unscrew the wingits and the interior part will just fall down to the bottom of the post. Then you can try a different mounting method.

 

[Jeff-in-MN]

That's what I'm doing (and I have been able to post pics before). When I preview the posts, however, I just see the generic "placeholder" image instead of my actual picture. I'll get it figured out eventually.

I'm not 100% sure if it will handle the weight, but I'm going to give it a shot. My bigger challenge will be, if I can't mount it safely and need to take it down, how to plug the two 3/4" holes I'll be drilling to insert the anchors. Hopefully I can find some kind of rubber cap or something if that's the case. Considering the 4 posts are holding up a pretty substantial cover and canopy (not to mention the constant flex/strain of pulling the canopy open/closed), I'm going to assume these legs are pretty secure. I realize that I'm putting a different type of force on the leg where I mount the TV, but it's a really small/lightweight TV. With the mount, it's less than 10 pounds total. I wouldn't be trying this with anything larger than the 24" screen I'm planning to put up.

Thanks,
Jeff

 

[SeniorSitizen]

Drill 7/32" holes and tap threads with a 1/4-28 tap for a fine thread cap screw/bolt. Put a little silicone adhesive sealer on the bolt threads to seal it to prevent water intrusion.

 

[huesmann]

If you need to fill the hole, use some paint and paint the uncoated steel on the inside of the hole, then use a rubber plug, e.g.: https://www.customled.com/products/3-4-rubber-plug-for-covering-oem-turn-signal-holes-pair

 

[Koa]

What about sandwiching the post between two 2X4s with bolts on the outside of post clamping the pieces of wood together? You could use ply also. Or metal brackets. No holes!

 

[Jeff-in-MN]

I thought about using liquid nails to attach wood to the post, and then using that wood to mount the TV. However, that won't fly with my wife, who doesn't want a TV out there at all. If I put one up, it has to be in a way that doesn't do anything to compromise the appearance of the the overall setup. I have to balance form and function to get to an acceptable final outcome.

--Jeff