Just bought a new home that has a dedicated area over the family room fireplace to mount a flat panel.

The builder framed an alcove with 2x6s then covered the 36"x48" opening with 3/4" OSB board and the drywall. I am leery of just mounting my 30lb bracket and then hanging my 75lb? 42" Panasonic by just using the lag bolts into the OSB board. Anyone have suggestions or experience with the same.

Thanks in advance

Just bought a new home that has a dedicated area over the family room fireplace to mount a flat panel.

The builder framed an alcove with 2x6s then covered the 36"x48" opening with 3/4" OSB board and the drywall. I am leery of just mounting my 30lb bracket and then hanging my 75lb? 42" Panasonic by just using the lag bolts into the OSB board. Anyone have suggestions or experience with the same.

Thanks in advance

If there's no stud to mount the bracket to then I suggest not mounting a TV there. If there's studs there then it shouldn't be a problem.

I confirmed with the construction super that ther are no studs and that it is osb board as a backer. He told me that they mounted real plasmas in the models without any problems. Think maybe I will go yank on those and see if they hold up :D I would be OK, if there were some kind of super toggle that I could use.

I wouldn't believe any builder using that crappy construction technique. Far too big a space to fill without studs. The OSB will probably warp. I'd be afraid he had attached the OSB board to the studs with duct tape or thumb tacks! Where is the power and the cable access?

Rip off the darn thing and add some horizontal 2" x 6" studs (face out) that are properly attached to the vertical studs he did manage to build. These horizontal studs should be placed so that the bracket bolts pass through the middle of the face of the studs. However you better make sure the vertical studs he built are well supported or go to the floor. Cover with wallboard.

Finally OSB tends to rip, so I wouldn't use a toggle.

Probably this is all over-engineering, but when hanging a flat screen it's the only way.

P.S. If you yank on the plasma in the model home, stand well back to avoid falling plasmas.

I agree. Crapppppy

The power is located in the alcove as is the duct for cables. I will investigate more today by pulling the outlet out to make sure the super isn't wrong and pray that there is a stud there. I am also taking a mirror to peak inside the wall because it is hard to tell if there are studs with the osb board and drywall.

Just bought a new home that has a dedicated area over the family room fireplace to mount a flat panel.

The builder framed an alcove with 2x6s then covered the 36"x48" opening with 3/4" OSB board and the drywall. I am leery of just mounting my 30lb bracket and then hanging my 75lb? 42" Panasonic by just using the lag bolts into the OSB board. Anyone have suggestions or experience with the same.

Thanks in advance

If you have any doubts about the strength, my advice is 'Don't try it!' Also generally speaking, placing a TV over the fireplace is not such a good idea. You may find yourself craning your neck to watch it, and the heat from the fireplace may be harmful over time.

I think you'll be OK with it, if you do it carefully. Use a wide-backplate wallmount (19" typically) with multiple thru-holes, which describes most of the backplates.

Normally you would use just two pairs of those redudant mounting holes, the ones that happen to line up with the hidden vertical wall studs. In your case, however, the wall support is distributed throughout the 3/4" wallboard, instead of being concentrated at the studs. Therefore, by using multiple fasteners spread evenly across the backplate, you will distribute the load more evenly across the wallboard and should be OK.

I would suggest maybe six #12 x 2" round-head sheet metal screws on both the upper and lower backplate hole rows, spread evenly across the backplate, plus two toggle bolts at the ends of the upper row. The toggle bolts will act as pullout retainers, and the screws will act as shear pins.

This should be absolutely no problem if you're just using a tilting (non-extending) wallmount.

I think you'll be OK with it, if you do it carefully. Use a wide-backplate wallmount (19" typically) with multiple thru-holes, which describes most of the backplates.

Normally you would use just two pairs of those redudant mounting holes, the ones that happen to line up with the hidden vertical wall studs. In your case, however, the wall support is distributed throughout the 3/4" wallboard, instead of being concentrated at the studs. Therefore, by using multiple fasteners spread evenly across the backplate, you will distribute the load more evenly across the wallboard and should be OK.

I would suggest maybe six #12 x 2" round-head sheet metal screws on both the upper and lower backplate hole rows, spread evenly across the backplate, plus two toggle bolts at the ends of the upper row. The toggle bolts will act as pullout retainers, and the screws will act as shear pins.

This should be absolutely no problem if you're just using a tilting (non-extending) wallmount.

OK, I went to the models today and they all have 46" LG Plasmas. They are all just tilt mounts and I couldn't see behind to look at the fasteners.

I bought an EXTENDING mount that I want to use. Darn. I think I am going to try it with screws (maybe molys that open up behind the osb board) and 4 1/4" toggle bolts. Once I do, I will, with the help of a friend, seriously pull on the whole kit and kaboodle to see if it holds. If it doesn't I will pick up the pieces and rebuild my alcove correctly. If it does hold....it's all good.

An articulating (extending) mount will increase the amount of pull-out tension on the upper fasteners, so using toggle or molly bolts on the top row is a good idea. Four should be enough, spread evenly across the backplate.

On the bottom row, screws should be sufficient as the bottom row of fasteners isn't subject to pull-out tension. In fact, the force on the bottom row of fasteners is to push in (and down) against the wall. I suggested #12 screws but, if you prefer, use the largest screws that the backplate will admit (most likely, 1/4"). At that size, they will be hex-head lag screws and you can use a wrench to tighten them -- don't overdo it and strip them out. Drill pilot holes first through the backplate, 1/16" smaller diameter than the screws.

OK, I went to the models today and they all have 46" LG Plasmas. They are all just tilt mounts and I couldn't see behind to look at the fasteners.

I bought an EXTENDING mount that I want to use. Darn. I think I am going to try it with screws (maybe molys that open up behind the osb board) and 4 1/4" toggle bolts. Once I do, I will, with the help of a friend, seriously pull on the whole kit and kaboodle to see if it holds. If it doesn't I will pick up the pieces and rebuild my alcove correctly. If it does hold....it's all good.

OSB degrades over time. I'm sure it would hold you just fine yanking on it. BUT over time, especially with an extending mount, your asking for trouble.
If you open it up and reinforce you can add conduit for pulling wires for your AV stuff and make it even better.

OSB degrades over time. I'm sure it would hold you just fine yanking on it. BUT over time, especially with an extending mount, your asking for trouble.
If you open it up and reinforce you can add conduit for pulling wires for your AV stuff and make it even better.

Hopefully the osb won't degrade to much (worried). They do use it in home construction so...

I will extend the arms infrequently and there is already conduit in the wall for wiring. Going to hook it up this weekend.