Finding the studs in an old lath and plaster wall

[albaPhenom]

I need to mount a tv to an old lath and plaster wall, circa 1950s... the wall has a recent skim coat on it and trying the magnetic stud finder method I can't seem to find any of the old rusty nails.

The stud finder as seriously strong magnets too and I've never had a problem finding studs in any other wall build-up previous to this.

Are there any tricks you know to find these or mount this tv?

 

[Deleted member 174758]

1950s seems late for a lath and plaster wall - Gypsum boards and plaster were introduced late '20s/early 30's so after WWII they became almost universal very quickly (in part because they are both faster to install and cheaper than lath). Either way the means of finding studs in both types of walls are similar - plasterboard until trhe 1990s was generally nailed to the stiuds with a type of galvanised clout nail whilst laths are nailed to the studs using what looks like a furniture tack. Both are steel, and therefore magnetic, and can be detected by slowly passing a rare earth magnet across the wall. Another clue might be in the skirtings, if they are original, where it is sometimes possible to make-out slight depressions in the surface of the skirting where it has been nailed to studs, punched under and filled (and the filler has shrunk slightly) - visible in a light held almost parallel to the skirtingh. Studs are invariable on 16in (not 400mm) centres, although this cannot always be guaranteed, and you'll always get a stud either side of a door opening as well as in a corner to start from by "dead reckoning" if you will.

 

[albaPhenom]

1950s seems late for a lath and plaster wall - Gypsum boards and plaster were introduced late '20s/early 30's so after WWII they became almost universal very quickly (in part because they are both faster to install and cheaper than lath). Either way the means of finding studs in both types of walls are similar - plasterboard until trhe 1990s was generally nailed to the stiuds with a type of galvanised clout nail whilst laths are nailed to the studs using what looks like a furniture tack. Both are steel, and therefore magnetic, and can be detected by slowly passing a rare earth magnet across the wall. Another clue might be in the skirtings, if they are original, where it is sometimes possible to make-out slight depressions in the surface of the skirting where it has been nailed to studs, punched under and filled (and the filler has shrunk slightly) - visible in a light held almost parallel to the skirtingh. Studs are invariable on 16in (not 400mm) centres, although this cannot always be guaranteed, and you'll always get a stud either side of a door opening as well as in a corner to start from by "dead reckoning" if you will.

Thanks for this.

Yeah the point about the age of the house was noted as 1950-ish but I suspect it's older than that (I've tried looking on old aerial photos to see if I can see it in old pre-1950s photos) as many of the building techniques used seem to be 1930s, unless they just had some old school builders involved in the construction.

It's 100% lath and plaster though, I had all the skirtings and architraves replaced when it got skimmed and took an old box-out around some pipes off exposing the wall build-up.

The skirtings boards might be a clue but I think the brads are just fixed into anything that happened to be behind where he shot the nail, the joiner I had in to do the work was f'kin terrible... I think I made a post about it at the time.

 

[Deleted member 174758]

If you've had the skirtings replaced then that's out, I'm afraid. When you pin skirtings on the skirtings are often actually fixed with a grip adhesive - all the pins do is hold the skirting up whilst the glue sets (really!) - so it matters little where you put the pins

So, I think I'd start at a corner then set out 16in centres to the approximate area you want your TV to go, then using a drill or an awl probe to see if you can hit a stud. This might take several attempts . Not what you want to hear, I know

There is, however, another way. It is possible to fix a pattress to a lath and plaster wall with oval nails (1-1/2 to 3in ones). Ideally the pattress should be either softwood or something like 9mm plywood, the nails should be driven at an angle downwards through the pattress and into the wall and the nails need to be orientated in the same direction as the laths (horizontal). This ia actually nailing to the laths, and you will need to use quite a few nails, and it will need to be as large as you can get it behiond the TV, but providing it is at least 20in (500mm) wide you will hold quite a bit of weight nand with any luck you'll hit a stud. I've used the same sort of technique to hand tyapestries in shops (off a 4 x 1 softwood plank) so I know it works. It's whether or not you are happy with disguising it

 

[albaPhenom]

If you've had the skirtings replaced then that's out, I'm afraid. When you pin skirtings on the skirtings are often actually fixed with a grip adhesive - all the pins do is hold the skirting up whilst the glue sets (really!) - so it matters little where you put the pins

So, I think I'd start at a corner then set out 16in centres to the approximate area you want your TV to go, then using a drill or an awl probe to see if you can hit a stud. This might take several attempts . Not what you want to hear, I know

There is, however, another way. It is possible to fix a pattress to a lath and plaster wall with oval nails (1-1/2 to 3in ones). Ideally the pattress should be either softwood or something like 9mm plywood, the nails should be driven at an angle downwards through the pattress and into the wall and the nails need to be orientated in the same direction as the laths (horizontal). This is actually nailing to the laths, and you will need to use quite a few nails, and it will need to be as large as you can get it behind the TV, but providing it is at least 20in (500mm) wide you will hold quite a bit of weight and with any luck you'll hit a stud. I've used the same sort of technique to hand tapestries in shops (off a 4 x 1 softwood plank) so I know it works. It's whether or not you are happy with disguising it

It might be an option to do that... I wish at the time I was in a position to pull these down and rebuild them with stud walls / plasterboard but it is what is for the time being.

Your posts gave me another idea, I could try to carefully strip that section of skirtings, mark the stud positions on the wall and re-fix the skirting board. It could possibly be less hassle and less intrusive than the pattress.

 

[JohnD]

You need my £50 Special Tool.

 

[Tigercubrider]

I remember my dad using a bent wire to find timbers in a lathe and plaster wall when I was a kid.
It does involve drilling a couple of holes though. But you could start by placing the holes behind where the TV will be.

from memory he bent a coat hanger into a U shape and got the first “probe” inside the wall and use the second to mark the wall angle where the internal probe hit a timber. It could mean a reasonable sized hole.

another suggestion is to go to the other side of the wall to see if your stud finder works better

 

[JohnD]

Is that you, son?

 

[foxhole]

Most tv plates I have installed are wider than any stud spacing, so just drive screws thru all the holes and at least two will hit a stud, more than enough.