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I've seen this question asked before, but didn't see what hardware to use in putting up the plywood.

I'm looking to mount my 65" TV above the fireplace using an articulating mount that mounts across 2 studs 16" apart. The problem: there is a stud in the center of the fireplace, leaving my TV off center when mounting.

Mount + TV weight: 74 lbs.

I've read you should use 3/4" plywood between 3 studs (16" apart) that is 3" more than the height of the mount and then put up the mount anywhere along the plywood. PLEASE CORRECT ME IF I'M WRONG.

If that mounting method is viable, what type of lag bolts do I use to mount up the plywood? I see so many different sizes that are available.

Also, once the plywood is up, do I use the lag bolts provided by the TV mount to mount the mount to the plywood? (that sounds weird lol) Lag bolts provided with the mount are listed as M8x55 Lag Bolts.

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  • I'd use 1/4-20, 5/16-18, or even 3/8-16, with a washer on the plywood. They'd all work as long as you have them evenly distributed & yea, the M8 would work
    – noybman
    Commented Sep 9, 2017 at 1:58

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The plywood plan sounds fine.

The lag bolts through the plywood into the studs need to be long enough to go through the plywood, through the drywall, and engage about 1-1/4" to 1-1/2" into the stud proper - not any further or you risk hitting electrical gear. For best results, pre-drill a hole into the stud somewhat smaller than the minor diameter (all-solid diameter) of the lag bolt.

It would also help to drill the plywood out to the major diameter (edge of thread) of the lag bolts. You don't want the threads engaging to the plywood, but rather, the stud. Worst case if the threads engage the plywood, it can end up causing the plywood to push away and then stand off from the wall, putting the screw entirely in shear, not its best strength. You want the plywood to be somewhat in compression against the drywall, the drywall's best strength (and tension is the screw's best strength).

The screws from the TV mount into the plywood need to engage into the plywood, all else is wasted. Since you will only have 3/4" of engagement, use lots of extra screws. They should also be snug.

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