help with hanging a plasma TV; stud orientation; urgent!

Hi folks,
I'm trying to help a friend hang his new 50" plasma (christmas gift!). The structure is as follows:
he wants to hang it over the fireplace. The TV+mount weight is about 115lbs, where about 90lbs (just the TV) can extend 26" from the wall. Anyway, I opened up a section of wall just to see what I can find (and to do the media cabinet wiring) when I noticed that the studs are placed in the other orientation from top to bottom. What I mean is that the wide edge of the stud (4") is facing the room as opposed to the 2" side.
Also, the stud can't go all the way to the bottom because of the fireplace, so just above the fireplace, the stud is attached to a horizontal 2-6".
Now, the plasma mount will catch two such studs, with 2 lag bolts in each that will be almost 2.5" long. Because of the orientation of the studs, the lag bolts will pretty much go thru the mount, drywall and stud (barely).
So my question is, is this structure sufficient to support this kind of weight, extended 26" from the wall as I've indicated?
Many, many thanks in advance.
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"axroh" wrote...

26" away from the wall seems like a lot, obviously it isn't one of those thin plasmas. You didn't mention what kind/type of fireplace it is. You should check the info on the fireplace to see if you are within safe clearances for the fireplace. There are a lot of unknowns here The closer you can get the mounting bolts to either the top or bottom of the stud, the less chance you have of deflection of the studs. Also the more thread or bolt area you can get into the stud, the less chance you have of the bolt pulling out. It might be worth pulling of the drywall to investigate and beef-up the structure.
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I know it's not what you want to hear, but that's probably a bad location for such a fine device. I lose this argument with the 'ladies who lunch' all the time, but a TV should be positioned *** AT EYE LEVEL ***, especially if you are going to *watch* it a lot.
To put both of these things in the same room is generally a mistake, unless the room can accommodate two furniture groupings.
--


MichaelB
www.michaelbulatovich.ca
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In a previous post axroh wrote...

Why do you want to hang it so far in front of the wall? I always thought that one of the purposes of flat screen TV's is to get them close to the wall.
FYI, lag bolts loaded in shear (sideways) with metal side plates should have a minimum penetration into the wood of 4 fastener diameters (pM). This will get you 50% of the shear load value. You need 8 fastener diameters (p) for full load value.
For withdrawal value of lag screws per inch of penetration use:
W= 1800 (G^1.5) (D^0.75)
Where G = specific gravity of the wood and D = fastener diameter
Example using Hem-fir framing: 1/4" lag bolts.
Pmin = 4D = 1.0", 8D = 2.0"
(2x flat) p= 1.5 inches shear capacity = 1.5/2.0 (130 pounds) = 98 lbs/bolt
Note: the 130 pounds comes from NDS Table 11K
Withdrawal value = (1800)(0.43^1.5)(0.25^.75)(1.5 inches) = 269 pounds per bolt.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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If you can get into the rear of the area, why use lags, use standard hex head bolts for those you can reach. If it isn' t built correctly, reinforce it with bracing.
There isn't a single person here who can tell you 'exactly' the best method. On-site-engineering is required.
MichaelB has a point as well.
DAC

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