Problem locating wall studs in outside wall

Forums › Home Workshop DIY › Problem locating wall studs in outside wall

neb

11294 posts

Uber Geek

Trusted

Lifetime subscriber

#199026 1-Aug-2016 15:15

I want to put in some shelving on two walls of a room, finding the studs on the inside wall went perfectly and I've got a pile of shelving anchored dead center into the studs (the Zircon i65 is pretty damn nice!). However, on the outside wall I'm getting completely random readings with both the i65, a Franklin 710 (which has a row of LEDs and one sensor per LED, so more a sort of wall radar device), and some no-name one from a friend. The readings are completely random, there'll be an apparent stud on one sweep and none on the return sweep, the sensors randomly indicate something or nothing, with the multi-LED Franklin the LEDs can blink on and off over one spot, and there's one region where there's apparently nothing for about 1.5m along the wall.

The wall is, AFAICT, gib, hollow-core (1970s house), then fibrolite cladding. There's no wiring or anything else inside the wall that can be detected by sensors. There's just no logical explanation for why the stud finders are acting like this.

If all else fails I'll try and line up the nails in the fibrolite outside with approximate positions on the inside walls, once I can locate at least one stud they're on about 16" spacings (the nails aren't dead centered so it's not exactly 16" for each gap), but since that may require some trial drilling or may end up off to the side of a stud I'd prefer not to do that.

Any ideas why I'd be getting results like this?

1 | 2

5816 posts

Uber Geek

ID Verified

#1602314 1-Aug-2016 15:19

What happens if you give the wall a good rap with your knuckles? Can you find the solid bits then?

richms

28215 posts

Uber Geek

Trusted

Lifetime subscriber

#1602315 1-Aug-2016 15:19

Ive had problems with the metal bracing straps in walls screwing up the studfinder. And also foil backed Gib makes the whole wall show as stud.

Richard rich.ms

andrew027

1286 posts

Uber Geek

#1602325 1-Aug-2016 15:26

Any particular reason you need to find the studs from the outside? How much load do the shelves need to bear that you have to drill through from the outside of the house to hang them?

trig42

5816 posts

Uber Geek

ID Verified

#1602328 1-Aug-2016 15:29

andrew027:

Any particular reason you need to find the studs from the outside? How much load do the shelves need to bear that you have to drill through from the outside of the house to hang them?

I think the OP means he cannot find the studs on the Outside wall of the room (not trying to find them from the Outside), whereas an internal wall is working fine with their studfinder.

neb

11294 posts

Uber Geek

Trusted

Lifetime subscriber

#1602329 1-Aug-2016 15:31

Yeah, tried the percussive stud finder :-). I haven't seen any evidence of metal straps (admittedly that was in another room), but hadn't considered foil-backed gib. Whatever it is it's playing havoc with multiple devices. If anyone knows of any magic tricks for this beyond the estimate-based-on-nails-in-the-fibrolite, I'd love to hear them.

Another problem with this room is that the previous owners used shaded, textured paint on it, so patching up the wall if I do exploratory surgery is going to be hard to cover up. It's not the texturing that's the issue because the same paint is on the interior walls which showed no problems.

mattwnz

20180 posts

Uber Geek

#1602341 1-Aug-2016 15:51

If a gib wall can't you push a probe in to see if there is a stud behind it? It is easy to fill the holes afterwards and you will have shelves covering it anyway.. It is probably as accurate as you will get. I have found stud finders hopeless and the ones I have tested have all been returned to the store.

neb

11294 posts

Uber Geek

Trusted

Lifetime subscriber

#1602342 1-Aug-2016 15:58

That's what the previous owners did, there's what looks like borer at one place in the gib there they just kept drilling holes until they hit a stud. I'm trying to be a bit less cowboy than they were :-).

In terms of stud finders, I've gotta put in a good word for the Zircon i65 (off Amazon, not paying the local prices), which does a really good job, on the interior walls I got the bolts perfectly positioned, and it has a good graphical display of what's behind the gib.

Sharesies

Trade NZ and US shares and funds with Sharesies (affiliate link).

SATTV

1649 posts

Uber Geek

ID Verified

#1602343 1-Aug-2016 16:04

I carry a couple of ex HDD magnets in my wallet, they are great as studfinders.

When the magnet stays on the wall it is on a nail or screw.

Then get a small nail and you can then tap it in either side of the magnet if you need to get more accurate.

john

I know enough to be dangerous

BlueShift

1692 posts

Uber Geek

#1602358 1-Aug-2016 16:12

SATTV:

I carry a couple of ex HDD magnets in my wallet, they are great as studfinders.

Doesn't that wipe all your mag-stripes?

Bung

6504 posts

Uber Geek

Subscriber

#1602362 1-Aug-2016 16:21

SATTV: I carry a couple of ex HDD magnets in my wallet, they are great as studfinders.

Great idea except for the wallet. Wouldn't the magnets nuke any mag stripes on your cards?

I find ex hdd magnets so useful that I'd never dump an old drive without taking the magnets out.

neb

11294 posts

Uber Geek

Trusted

Lifetime subscriber

#1602363 1-Aug-2016 16:23

Probably not, standard bank cards and the like will be HiCo (high coercivity), so a magnet won't do much to them. Library cards and the like are more likely to be LoCo, but then the Auckland library ones use barcodes anyway so they're not much affected by magnets.

richms

28215 posts

Uber Geek

Trusted

Lifetime subscriber

#1602365 1-Aug-2016 16:29

All my strips get erased all the time anyway, nothing uses them except for ATMs, so I just get my eftpos card replaced when it stops swiping, the others are chip so no need to worry unless I want to travel to backwards contries like the US.

Richard rich.ms

Fred99

13684 posts

Uber Geek

#1602369 1-Aug-2016 16:37

Hah - maybe with fibro cladding, all the external studs have rotted away so only the fibro and gib are left holding the roof up.

Only kidding. Sometimes I can't get stud finders to work. I like the magnet idea - up to the point you're working in a wet area fixed with SS screws.

1.5mm drill bit is my goto option, very easy to fill the holes with a ready to use filler - or just forget about them if you can drill the holes at the level where they'll be behind the shelf. I'd have said a 1mm drill bit, but they don't fit in the chuck of the drill I usually use and they also tend to snap very easily - I'd need to have a few spares handy.

RunningMan

8964 posts

Uber Geek

#1602388 1-Aug-2016 17:21

richms: [snip] And also foil backed Gib makes the whole wall show as stud.

This is almost certainly the problem in a '70s house. Other than the foil, no insulation as well!

neb

11294 posts

Uber Geek

Trusted

Lifetime subscriber

#1602402 1-Aug-2016 17:53

RunningMan:
This is almost certainly the problem in a '70s house. Other than the foil, no insulation as well!

Yeah, all the houses in the street are uninsulated. Some of my more ambitious neighbours have gone through room by room ripping off the gib, adding insulation, and putting on new gib. Bit too traumatic for me to do that here...

1 | 2