Mounting Question - Plywood to Ceiling

[JohnLew]

I think this should be plenty but want to double check. I am mounting a BenQ LK953ST using a Chief RPMAU mount with no extension column so it will be mounted flush (I want the PJ as high as possible). The spot I want it in won't allow it to be directly mounted to the joists and I didn't put any 2x4 blocking there.

Right now I have mounted two sheets of 3/4" plywood to the ceiling across 3 joists using 3 1'2" construction screws. So the plywood is hitting all three of those joists.

My plan is to mount the RPMAU to the plywood using 3" lag screws. The PJ weights 20-22 lbs.

This should be plenty of strength to not have to worry about this thing, right?

[3on3putt]

It should be more than fine. I did something similar because I didn't have any studs in the spot where I needed to attach the mount. So I ran a piece of plywood that's maybe 2 feet by 3 feet that is screwed into two studs and then the mount is attached to the plywood. You shouldn't have to worry.

[timsiegle]

I wouldn't use 3" screws to mount to the plywood, just long enough to barely make it through is all you need. Any longer than that won't get any more strength out of it.

[jasonreg]

I wouldn't use 3" screws to mount to the plywood, just long enough to barely make it through is all you need. Any longer than that won't get any more strength out of it.

+1. Thicker, wood specific screws as well is my recommendation. #10 + 1" wood screws are what I used in the exact same application.

[JohnLew]

Thanks, everyone. I should have been more specific on the screw length. That Chief RPMAU Elite holds about 1-1/2" of the screw in the mount, so the whole screw isn't exposed beyond the mount. After accounting for this, the 3" screw was just enough to get through the two sheets of plywood.

Hung it last night and I could probably hang upside down from it without moving so should be good

[fortner28]

Wow. That is more than enough to have zero worries of the unit falling. As the others have said you only need a screw to penetrate about an inch into the joists. More penetration isn't going to hurt anything but it wont make it stronger.

[jasonreg]

oh the places this thread could go ....moving on....