Mounting a TV on a 5/16" thick stone (or faux stone) facade

Question

I'm planning to mount a 65 inch TV (62 lbs) over my fireplace using this pull-down mount.

The fireplace has a stone facade as shown below. It may be faux stone, I'm not sure - the individual stones are 1/2" tall, and 1-1/2 to 3 inches wide. Viewing it from the side and measuring, it appears to be about 5/16" thick. Underneath it I believe there are ordinary drywall and studs. My stud detector was able to locate the studs without much trouble on the 1-1/2 inch setting (marked with electrical tape below), and I confirmed by finding the nails in the studs with the metal detector setting.

I've never worked with stone before. My plan was to rent/buy a hammer drill and some masonry bits. I start with a small pilot bit (like e.g. this carbide hammer drill bit), go slowly, wear safety glasses, and then gradually enlarge it until I reach the diameter of the lag bolts that I want to use (probably 5/16" diameter). Then I use my regular drill to get through the drywall and the stud. I use a slightly smaller diameter like 1/4" for the studs so that the bolts can bond with it. The lag bolts should probably be 3" long to account for the mount's wall plate (1/4"?), the facade (5/16"), the drywall (1/2"?), and finally 1-1/2" or so into the stud.

What I'm not sure about here is: is this the appropriate technique for this kind of facade? I feel like this is probably faux stone and very thin and that I'm probably being excessively cautious, but I don't want to crack or crumble it, or destroy my drill or drill bits.

I consulted these earlier posts: What type of screws and drill bits should I use to mount a mantel over faux stone?, What is the right drill bit for concrete or stone walls?

Answer 1

I spoke to the builder about this project and he said "if you can locate the studs and make sure most of the bolts end up in them, it should be able to handle the load easily." He made the following recommendations:

Make sure you use all mounting holes if you can - for those that don't hit the studs, you can use either toggle bolts or pop toggle anchors. The tiles are mounted on Hardie tile backer boards, if I remember correctly, so it should be fairly sturdy.

In my case the mount features two rails with 33 holes in each, designed to accommodate a variety of distances between studs. They're only intended to be bolted with lag bolts to two studs, but it certainly can't hurt to use toggle bolts on some of the other holes for a little additional support. The wings are usually a little wider than the bolt diameter and it needs to fit through the holes on the mount, so I got a toggle bolt assortment of 1/8", 3/16", 1/4".

If drilling through that mosaic tile starts chipping the tile, you may want to consider using the diamond drillbit holesaws. They're easier to use and leave any tile holes much neater looking.

I think a diamond holesaw is a great idea and I picked up this set which should accommodate the 5/16" lag bolts. I can still use my small 5/32" carbide bit to drill a pilot hole to help prevent the hole saw from slipping.

I also watched this YouTube video on drilling in tile which made the following recommendations to prevent the drill bit slipping that I found useful: 1. use masking tape over the area where I will drill; 2. use a center punch to create an indentation in the spot where I'll drill by lightly tapping with a hammer. I found this tungsten carbide tipped center punch that should do the trick on a hard surface.

I also found some advice online to take short breaks to let the drill bits cool between holes, and/or to dip them in water frequently to cool and reduce dust.

Answer 2

If this was my house, I’d drill into the studs on the marks, and try to screw through the grout, preferably into one of the areas where the stone corners are chipped, or any area with lots of grout because it easy to drill through grout.

But yeah this will run the risk that when you start to tighten the screws the grout and or stone might crack. And you might miss a stud, I understand you are concerned about that.

So I’d use two wood stringers. Either clean 1x4 or a few pieces of plywood. You can adjust these up or down so you can find the best place for screws to land. Again, try to drill through grout. I assume your mount is two vertical pieces with lots of holes.

Stringers are red

Your mount is blue

Possible places to drill are black

A benefit to this approach is that if one screw misses or doesn’t land dead center, you have another one to pick up the weight. Another benefit is that tightening the screw on wood will allow the wood to compress and not crack the grout. This is a benefit of using pine 1x4 because they’ll compress.

Assuming this is a normal tv, I’d use heavy duty construction screws. Probably #9 screws. I would skip the 1/4” lag bolts. Construction screws will hold the weight and keep the holes to a minimum.

The tricky part will be aligning the holes in the grout with holes in your stringers. You can go this using tracing paper, plexiglass, or a trick using masking tape. Those are some methods that will allow you to transfer the location of the holes perfectly onto your stringer.

If you want even more options for holes, use a rectangle piece of plywood. This will allow you to put your holes with much more height variability, and if you make it sort of random, any future repair will be harder to spot.

Answer 3

This mount presents the wall with a combination of weight, leverage, motion and human handling. It's a lot. I would be afraid that over time it will cause cracking in the facade or pointing.

Also you have to get the lag bolts dead center on the studs, and I think that's extremely difficult through the stone.

Me, I wouldn't use that mount there. Or put a TV there. But anyway, I think a safer way to do this would be to approximately find the studs, remove the entire facade behind the TV mounting bracket, enough to accommodate it plus a quarter inch all around. Then drill tiny pilot holes to exactly locate the studs and mount the bracket on the drywall. Fill the gap with flexible caulk then paint the whole thing as designed.

I might go a step further and remove the drywall too to inspect the framing and make sure it's up to the task. You are really asking a lot of it.