Stud finding confusion - Can only seem to find 1 in 2

[HedleyP]

Hi,

I'm pretty/totally clueless when it comes to houses and building so please bare with me...

We've just moved into a new build house (2005) and I'm trying to find the studs to hang an LCD tv.

From what I've managed to find out by talking to a few people who talked far too quickly using terms I found hard to understand: It's a timber framed house with plasterboard on studs then sheet (I'm assuming this is something like OSB?) EDIT: Just found out this is called Sheathing, not Sheeting then a membrane then block with render on the outside. Internal walls will I assume be just stud with board on them.

The external walls are filled with millions of small polystyrene balls and the internal walls with the yellow stuff you see in attics.

The wall I'm trying to attach the tv to is an external wall.

I can see the joins/nails between the boards and they are 1200mm apart. If I tap these areas they sound like there are studs there and my finder also spots them. All good so far.

I can also tap and find studs 600mm between these joins with nails visible. But my finder never spots these.

Q1) Would I be right in assuming that the board has some type of lining on the back that is preventing the finder from seeing the middle studs but the gaps between the boards let it find them?

Q2) 600mm is 23", isn't this much wider than normal for stud spacing?

Q3) If I am to feed wires down behind the board from the tv to the socket on this and internal walls, will the insulation pose a problem. How would I prevent an avalanche of small balls from pouring from the wall if I cut holes for cable plates, would I need to drill small holes around the area and inject expanding foam or something?

I also plan to whip off a socket and have a poke around behind with a mirror and torch to try and get a better idea of what's behind there.

Thanks for your help, it's appreciated.

 

[pinenot]

Here is Trada's model of a timber frame walling: View media item 57459 When you say external wall "full of millions of small polystyrene balls" do you mean between the brick facade and the timber frame or immediately behind the plasterboard i.e. between the studs.
600mm between studs is standard wall construction nowadays and the vapor barrier could be metal foil on the back of the plasterboard confusing your stud finder.
The other standard spacing between studs is 400mm both this and the six hundred replace the old imperial settings of 18" and 24"
I've never come across polystyrene beads being used in timber frames, normally its rockwool, as in your internal walls. That would present a problem in cutting any holes in the wall, but if you have a controllable expanding foam gun, you could provide four or so holes around the cut shape just large enough for the point of the gun to push through into the cavity behind, and squeeze of some expanding foam. When this has dried/solidified the area of cut should be fairly stable...pinenot

 

[HedleyP]

Here is Trada's model of a timber frame walling:

Thanks for that. That makes a lot of sense. Helps to be able to visualise what's in there.

When you say external wall "full of millions of small polystyrene balls" do you mean between the brick facade and the timber frame or immediately behind the plasterboard i.e. between the studs.

Yes, it was immediately behind the plasterboard but I'm probably wrong here. It's the garage wall that's full of these balls and I then went on to assume that the house would be the same. I need to have a peek and double check.

600mm between studs is standard wall construction nowadays and the vapor barrier could be metal foil on the back of the plasterboard confusing your stud finder.
The other standard spacing between studs is 400mm both this and the six hundred replace the old imperial settings of 18" and 24"

I'll test the rest of the wall to see if the studs in the middle of the board aren't detected and then we can be certain that it must be a foil backed barrier. Glad my house has been built to a standard.

The foil is going to make testing for pipes and cable a little tricky though.

I've never come across polystyrene beads being used in timber frames, normally its rockwool, as in your internal walls. That would present a problem in cutting any holes in the wall, but if you have a controllable expanding foam gun, you could provide four or so holes around the cut shape just large enough for the point of the gun to push through into the cavity behind, and squeeze of some expanding foam. When this has dried/solidified the area of cut should be fairly stable...pinenot

Thanks for the tip, I can use that in the garage if required.

Brilliant, I feel a lot more confident now and ready to crack on. Didn't like not knowing how it's built, doesn't seem right.

 

[pinenot]

The tapping method is by far the best in my opinion, you can follow that by tapping in a thin panel pin of suitable length to find both sides of the stud and thereby the center where you want a fixing to go, until you get used to this method...pinenot

 

[Norcon]

Neodymium disc magnets for a few quid are by far the best way to find a stud.

8mm in diameter and about 6mm long.
Just hold them against the wall and they soon form a line of magnets down the stud sticking to the nail or screw head.

That's the mother of all top tips.