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Stud finding mystery

Magic Beans

Active Member
I'm about to mount my Sony KDL-40W4000 on a plasterboard covered stud wall. I've got the VESA mount etc sorted and have used a stud finder to locate the wall studs. However one quirk i've found is that the locator finds solid points in the same spot as i find (using the old wall tapping technique). But if i run it vertically down from the solid part, it doesn't find anything until it hits the next solid part (wall tapping confirms this).

The mystery is that if the studs are vertical, or even horizontal, then why does the wall sound hollow between the gaps from one solid sounding area to another? Surely if they run down the wall, then the plasterboard would fix straight to it, right? Or am i finding lumps of some sort of compound which is is fixing the platerboard is set locations and the studs are actually recessed slightly further back?

Does that make sense? :confused:
 

owen021173

Well-known Member
are you sure its a timber stud wall and not dot and dab ????

if you can, try peeling the skirting away from the wall and chisel a bit of plasterboard out to see if you find either a timber sole plate or block work behind.
 

thorpe

Standard Member
generally speaking with stud walls you would expect the boads to be fixed direct onto the studding but what your describing would fit in which dot and dab. An adhesive on the back of your boards pressed against the wall hence youve got an apparent solid point followed by a void until you reach the next solid point

i have seen plasters dot and dab onto stud walls but its not good practice as far as im concerned, it could of course be that youve got old stud lath and plaster walls in which case someone may have dot and dabbed over them but like i said you'd really only expect dot and dab onto solid walls not stud walls

or like above it could just be the noggins your detecting as a more solid sounding point
 
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jont

Well-known Member
If it is dot and dab then a useful tip is to drill the holes for the vesa mount and then get some plasterboard adhesive in a tube and squirt it through the holes to create 4 new dabs providing the solid bond and strength in just the right places ...

Jon
 

Magic Beans

Active Member
Thanks for the answers :thumbsup:

I've been "assuming" it's studs and not block work. However now you mention it, it could well be block with dot and dab fixing the plasterboard to the brickwork. The house is only 6 years old, so i know it's the same setup as when it was first built.

Generally, how big is the gap between the blocks and the plasterboarrd?
 

uk_zio

Standard Member
That sounds exactly the same as when i put my 32" samsung on a internal wall in my house. Its due to my house being only 10 years old that they have come away from studs and now use a sort of mixture that solidifies like brick when placing plaster board on to breeze block or brick work. In the end i just made sure i used long enough and enough heavy lifting screws that went straight in the breeze block.
 

thorpe

Standard Member
entirely dependent on how much adhesive they used and how straight the wall was in the first place but generally speaking id say your looking at about a 5mm void as a minimum
 

Magic Beans

Active Member
I've done some "tests" and it's definatly block work and a plasterboard layer on top :thumbsup: Feel stupid for making the assumption it was studs without testing it :rolleyes:

So theoretically, it "should" just be a matter of using long fixings and drilling through the board until i reach the blocks. Just in case, i'll hold off starting it until the weekend. In case of any dramas ;)
 

thorpe

Standard Member
indeed some long fixings straight into the block work

if its thermalite blocks (breeze blocks) then we always go with a resin fix as they are prone to fracturing not a problem in that the surrounding block work will hold it in but overtime movement may lead to a little crumbling round the fix inturn allowing it to become lose. Some will say its fine going with standard raw plugs and screws and they are proably right but the fact is adding the resin will lead to a stronger fix.

if its concrete blocks or brick then its dependent upon the weight, rule of thumb we use at work has always been anything below a 28-32 inch screen size can be mounted with raw plugs and screws. Anything bigger than that and we overkill it with steel anchors. Again though some will argue otherwise and swear that raw plugs and screws will do just fine but again a steel anchor is the better fix and it makes me sleep soundly knowing that the customer can swing from their telly without it falling off

the only other thing to say is dont use the provided raw plugs and screws which come with the mount they are always cheap and rubbish
 

Magic Beans

Active Member
indeed some long fixings straight into the block work

if its thermalite blocks (breeze blocks) then we always go with a resin fix as they are prone to fracturing not a problem in that the surrounding block work will hold it in but overtime movement may lead to a little crumbling round the fix inturn allowing it to become lose. Some will say its fine going with standard raw plugs and screws and they are proably right but the fact is adding the resin will lead to a stronger fix.

if its concrete blocks or brick then its dependent upon the weight, rule of thumb we use at work has always been anything below a 28-32 inch screen size can be mounted with raw plugs and screws. Anything bigger than that and we overkill it with steel anchors. Again though some will argue otherwise and swear that raw plugs and screws will do just fine but again a steel anchor is the better fix and it makes me sleep soundly knowing that the customer can swing from their telly without it falling off

the only other thing to say is dont use the provided raw plugs and screws which come with the mount they are always cheap and rubbish

I've had a couple of sockets off and they look like thermalite blocks. How do you apply the resin? Drill the holes, fill them with resin and then stick the bolts in?

The mount weighs 6.5kg and the TV weighs 18kg, which isn't bad for a 40" LCD :eek: I'll go and pick up some heavy duty lag bolts and plugs at lunch. I'll grab some resin at the same time :thumbsup:
 

thorpe

Standard Member
yeah fundamentally your drilling holes, sucking out the dust with a vac injecting your resin and fixing

theres a picture instruction diagram on resin fixes here
Fischer Hybrid Mortar Resin V 360 - Screwfix.com, Where the Trade Buys

and assuming theres a screwfix near by you can get all your bolts, plugs, and resin there, you dont need to go with the branded resin and you dont need to by an injector kit just go for one of the tubes which work via a standard sealant gun

i was searching and found http://www.avforums.com/forums/custom-installers-installations/771036-50-plasma-breezeblock-thermalite-mounting.html got an explanation on resin fixes, but it also has some info about rigifix the guy is quite right in that they are more than suitable, but it doesnt detract from the fact that overtime block does crumble round the fix and so it could become lose. It just a question of will it be 6 months down the line or 25 years later and thats dependent upon how much movement there is if its a fixed mount then theres no movement beyond that of installing the tv in which case your fine, if your on an swivel mount and swinging it round then theres going to be movement.
 

Magic Beans

Active Member
yeah fundamentally your drilling holes, sucking out the dust with a vac injecting your resin and fixing

theres a picture instruction diagram on resin fixes here
Fischer Hybrid Mortar Resin V 360 - Screwfix.com, Where the Trade Buys

and assuming theres a screwfix near by you can get all your bolts, plugs, and resin there, you dont need to go with the branded resin and you dont need to by an injector kit just go for one of the tubes which work via a standard sealant gun

i was searching and found http://www.avforums.com/forums/cust...0-plasma-breezeblock-thermalite-mounting.html got an explanation on resin fixes, but it also has some info about rigifix the guy is quite right in that they are more than suitable, but it doesnt detract from the fact that overtime block does crumble round the fix and so it could become lose. It just a question of will it be 6 months down the line or 25 years later and thats dependent upon how much movement there is if its a fixed mount then theres no movement beyond that of installing the tv in which case your fine, if your on an swivel mount and swinging it round then theres going to be movement.

Thanks :thumbsup:

Just been to Wickes and picked up some "Vinylester Injection Resin" and a pack of 6 M10 x 130mm coach bolts. :eek:

I take it the hole needs to be small enough so the bolts can screw in, but large enough so the resin can surround the bolts?
 

thorpe

Standard Member
you'll want the hole 2-3mm larger than the bolt, the resin is just like a raw plug except it penetrates into the block itself, you could stick in a raw plug as well if you wanted but shouldnt be needed (just have to be careful some resins eat the plastic of the raw plug)

As my old boss taught:

if its going into wood you want the hole to be no bigger than the shank, this then gives the thread of the screw/bolt something to bite into

if its masonary you want the hole to be 2-3mm larger than the diameter of the screw/bolt, basically big enough for your raw plug to go in which creates a sleve for the thread of the scew/bolt to bite into as you drive it in

do check how big the void is behind the board as you may want squeeze in some adhesive to take the whip out of the board immediately around where your tightening the bolt into (It will also stop you tightening the bolt so much that it goes through the board)

breeze block doesnt need hammer action when drilling, it will just tear straight through the block, just normal rotary action with a little pressure to the required depth

and if the resin tube says wait 24hrs before hanging anything of weight on the fix then do wait
 

Magic Beans

Active Member
Everything was on travk. However the resin was partially set, even before it came out of the tube! :mad: Back to Wickes today to get it swapped.

However... I did manage to get two in and they alone could hold up the Earth! :eek: So hopefully, once the other two are done, we'll be ready be roll.

Masonary threw in few curve balls but it'll be done be this afternoon :clap: Apparently it only takes 40 mins to set. However i'll leave it until this evening and get the other jobs done in the meantime.

Wish me luck ;)
 

albriscoe

Distinguished Member
If it is dot and dab then a useful tip is to drill the holes for the vesa mount and then get some plasterboard adhesive in a tube and squirt it through the holes to create 4 new dabs providing the solid bond and strength in just the right places ...

Jon

what a dam good idea Jon

see the simple things are usually the best

cheers Al :smashin:
 

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