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condoowner 04-01-2012 06:27 PM

Wall mounted TV, problems with finding the studs
Hey there! Ive recently moved and I am looking to mount my flat screen TV on the wall of my new condo's living room... In my last property, I installed the TV on the wall in about half hour without a single glitch, but now, I am having problems..

Please note I am trying to mount th TV on an exterior wall (should be 5/8 drywall with 16" C/C studs here in Quebec).

First of all, I am using the same stud finder as I have been using for the last few years (an electronic Stanley stud finder with digital display). This device has been working very well and Ive done several dozen of jobs with it, never had a problem. When the thing beeped, sure enough there was a stud behind.

Now I am using the stud finder to "find the studs" but the problem is that the finder behaves very strangely..

In the past, my technique to double check and confirm, has always been to do a first pass on the wall, mark up where the finder would beep, and then perform a second pass coming from the opposite direction (lets say left to right the first pass and then right to left on the second pass). If the scanner beeped at the same location for both passes, I'd trust there was a stud behind.

To summarize:

-it beeps at irregular intervals.. (not every 16", but like 16 - 12 - 28... !?!?)
-it doesn't always beep at the same place twice, it would beep about 3 to 4 inches away from the pencil mark I made during the first pass..
-sometimes, it doesn't even beeps on the second pass (like if the stud had disappeared..)

Another technique I would use to double check, was to look for visible drywall screws and if they were aligned roughly with the location where the stud finder beeped, this would confirm there was a stud there..

What Ive also noticed with this job is that the drywall screws are all off by 3 to 4 inches from the location of the studs (as found by the finder).

So what Ive done is to use a potential stud (because the finder beeped during both passes and there seems to be some drywall screws around there) and trace a line 16 inches apart (where the next stud "should" be). Then I've drilled a small (3/16") hole for my TV mount screws and discovered something funny..

The drill bit went through the drywall without problem. Then Ive withdrawn the bit and inserted a screwdriver to "poke" the stud and confirm there is something behind. Sure enough there is "something" but its 1 1/4" from the drywall face.. If it was a stud, it should be 5/8" deep (the thickness of the drywall sheet) right??

So I am clueless.. Could the stud finder be screwed up by electrical fields or something else? What have I "poked" behind the wall? Unless its something else other than a stud, this would mean that the drywall is not touching the stud which is not good at all.. All I know is that whatever I've poked is firm and sounds like wood (not mushy and spring like action like a wire or tube/pipe)..

As you can see, its giving all kind of inconsistent results.. I cant trust anything. Should I simpy use the "possible" drywall screws or scan the studs some other way?

Anybody can clarify/give guidance?


nealtw 04-01-2012 09:18 PM

With your knuckle bump the wall, you will hear the different sound where the stud is. If you are working over a fireplace, all bets are off on what you will find and where.

condoowner 04-02-2012 05:29 PM

OK so ive managed to progress somehow... Ive drilled a pretty big hole (3/8) right where the stud finder would find a stud, then I took a flashlight and saw what appear to be a plastic envelope. I assume this is for the insulation. Then I poked and felt either a stud or something else rather strong. I am 99.9% confident this is a stud.

Then Ive measured how far the "stud" was from the inner face of the drywall and got 1.25". Then Ive measured the drywall thickness and roughly got 1/2". This would mean that there is a 3/4" gap between the stud and the drywall... nonsense as the wall would be "bouncy" and all the drywall joints would be bad..

Im not sure what to think. Then I drilled an identical hole right where I could see some drywall screw heads, and this is only insulation behind ( I can sink a 2"+ screwdriver and it feels mushy)..

What to think? Why is there such a huge gap ? Why would the drywall screws be located between studs??

I dont know what to think as Ive never seen this before...
Anybody can shed some light on that?

nealtw 04-02-2012 05:45 PM

By now I would have a big hole in the drywall. I would open it up and add solid blocking between the studs and repair poly and drywall. Keep the patch behind where the TV will sit and your fill job will be hidden.
I could make a guess at what your finding but it wouldn't be worth much.

condoowner 04-02-2012 06:11 PM

I agree with you but this wall is an exterior wall and is property of the condo corp so If I start tearing it apart they will tear me apart ;)

Id prefer drill my 4 holes in the studs, mount the TV, and whenever I move, I just patch and paint touch up like I did in my last condo. Nobody ever knew I drilled the condo studs.. :)

My question is more: is it possible to have such a gap B/W the studs and drywall? Is it part of some construction techniques? I might climb up the attic and look at the wall from "outside".. I may see the studs on top/below the insulation?

nealtw 04-02-2012 06:18 PM

My guess is that somewhere on that wall is a beam or a post that was thicker than the wall, so they strapped it with 3/4" boards, every 16 or 24" so run your studfinder up and down the wall, the boards will be 3 1/2". But that's just a guess.

condoowner 04-02-2012 06:41 PM

The question is: Would you trust the studs ive found to mount a 55 inch tv?

Ill go as a minimum behind the wall to see what I can see but if I cone back unsuccessful, ill be left with only guesses to work with.

Since the beginning ive had the feeling there was horizontal bars behind the drywall. Im not sure what you are trying to explaining. I understand the beam (vertical? ?) That could be thicker but where I get lost is with the 3 1/2 bars..

Can you give a link where I can see a picture of that? Or explain a bit more?


nealtw 04-02-2012 07:20 PM

It is still just a guess but I am thinking they put 1x4 lumber straping horizontal across the studs. A 1x4 measures 3/4 x 3 1/2 inches. If you can prove that is what you have, you will want to mount the TV mount so that the screws go thru the 1x4 and into the studs.

condoowner 04-11-2012 01:09 PM

Turned out you were exactly right! Its 1x4 strapping screwed horizontally across the wall, with 16in C/C. I wonder why they did that... the wall doesnt seem bent or curved at all... To reinforce? Its a load bearing wall so my guess goes on strength.

Anyways now that we have cut a hole about 14inx8in right between 2 studs, we can examine the situation better. What we will do is insert 2 12in pieces of 1x4 (exact same stuff as whats already there) between the drywall and the studs (one on each side) and then screw them on the studs. Then we will use the width to close the hole with a drywall piece and drill thru the spacers (these pieces of 1x4) the drywall and into the studs.

Should be really strong. I will just need to find some wood screws that are 3/4" longer than whats provided in the wall mount kit.

Thanks nealtw for your help!

nealtw 04-11-2012 02:13 PM

The strapping wouldn't add strength but it might be there to hide a header, thicker than the wall or a concrete curb or evan a water line that wants to be inside the insulation.

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