What's inside my walls?

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Lizard1977

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#293938 23-Feb-2022 09:43

I bought a 1960s ex-state house late last year (weatherboard cladding), but have encountered a few oddities with some of the walls. Last Sunday I was fitting a shelf in my bedroom. The area of wall where the shelf was going to go is external on the other side (by the front door, adjacent to the meter box). I used a stud finder to find the stud, and measured out the corresponding hole to drill a pilot for the plasterboard anchor I was going to use. But once the drill got past the plasterboard it met serious resistance. It definitely didn't strike wood - it felt like concrete or maybe even metal, but it wasn't a nail or screw head. I drilled test holes in a matrix pattern over an area of about 40cm x 20cm (gave up as I didn't want to drill more holes in my wall) and all met the same resistance. I wondered if maybe there was some kind of metal plate behind the plasterboard, but I couldn't imagine why (unless it was related to the meter box somehow). I had a similar problem in the utility room adjacent to my laundry. When I tried to fit the charging bracket for my Dyson, I ran into similar resistance, but in that case I was able to simply move across and find a different stud to fix it to.

I'm not a builder so I don't know what's back there but I wouldn't expect to find concrete or steel behind plasterboard in a house this age. Shouldn't it just be timber framing?

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#2873127 23-Feb-2022 10:22

You may have been unlucky enough to strike a steel water pipe

Lizard1977

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#2873134 23-Feb-2022 10:28

All the water-serviced rooms are on the other side of the house, so I would be surprised if it's a water pipe of some kind, especially running through the wall. Wouldn't it run underneath and then come up into the rooms where water is needed? In this specific part of the floorplan it would have to come in from the street, under the house, up the wall, go around the doorframe and into the ceiling, and then back down the wall and snake it's way into the kitchen, so I don't think it's water.

frankv

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#2873137 23-Feb-2022 10:30

larknz: You may have been unlucky enough to strike a steel water pipe

No... 400 x 200mm pattern found it.

I'm thinking perhaps hardboard? This was used as wall linings for a while, and they may have subsequently just nailed Gib over the op of it?

pih

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#2873146 23-Feb-2022 10:40

You didn't actually hit the meter box, did you? 😉

Other alternatives:

Was the room an extension or alteration? Perhaps what is an internal wall now was originally external and they've just slapped gib over the original fibre cement (asbestos?) cladding?

Could be steel bracing, although with the area you've tested this is unlikely, it's usually a diagonal strip

Or maybe you hit a time capsule or treasure box! Only one way to find out...

Lizard1977

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#2873153 23-Feb-2022 10:50

In my previous house (a 1920s bungalow), we had sarking behind the gib. We put up plenty of stuff on those walls but never encountered this kind of resistance. But I suppose it could be something like that. It would mean either my drill bit is horrendously blunt (it is, but I didn't think it was that bad) or my drill is horrendously underpowered (it is, but I didn't think it was that bad).

I did wonder about the meter board, but it's not directly opposite - unless there was a much larger steel plate that it was attached to, but I just presumed it would have been screwed into the framing (unless they did things differently in the 60s). Also, I only went about 12mm in. If I did hit the back of the meter board box then it's butting up against the internal lining.

The floor plan hasn't been altered or extended (at least, not on this side of the house). The other side of the wall is external (the entranceway to the front door), but as far as I know it's original cladding was weatherboard rather than fibre cement.

I guess I could cut a hole out and take a proper look, but it's a fairly prominent part of the room, and my skills in patching the plasterboard are probably not good enough to repair said hole without living a visible trace.

MikeAqua

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#2873218 23-Feb-2022 12:10

Old rimu sarking can be very, very hard. Can you get a metal object into the hole and tap it? See what it sounds like.

Mike

SepticSceptic

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#2873566 23-Feb-2022 23:18

Grab a fibre optic endoscope camera. 30 odd bucks on Aliexpress.
Only needs a 5.5mm hole.

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Bung

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#2873578 24-Feb-2022 03:45

He doesn't have a hole yet. If you already have drilled a pattern of holes into gib, join up the dots and remove a small piece of gib. You'll be able to glue it back in. It is possible you do have a steel plate protecting cables if it is close to the meter box.

neb

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#2874051 24-Feb-2022 14:06

MikeAqua:
Old rimu sarking can be very, very hard. Can you get a metal object into the hole and tap it? See what it sounds like.

Or get a borescope camera from one of the usual suspects. If you're on the north shore you can borrow my one. Those things are worth their weight in gold when you're dealing with dodgy renos and fixups.

duckDecoy

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#2874063 24-Feb-2022 14:19

SepticSceptic: Grab a fibre optic endoscope camera. 30 odd bucks on Aliexpress.
Only needs a 5.5mm hole.

Which would you recommend from Aliexpress? I see a bunch on there but know zero about this stuff.

neb

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#2874068 24-Feb-2022 14:23

duckDecoy:
Which would you recommend from Aliexpress? I see a bunch on there but know zero about this stuff.

Almost any will do, just make sure they have a ring light and a clip-on 90 degree reflector so you can see sideways along the wall, most will have this anyway. You can also get them on TM for under $20 if you don't want to wait a month or more for Ali.

MikeAqua

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#2874101 24-Feb-2022 15:04

neb: Or get a borescope camera from one of the usual suspects. If you're on the north shore you can borrow my one. Those things are worth their weight in gold when you're dealing with dodgy renos and fixups.

Or mystery leaks in cars

Mike

Bung

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#2874102 24-Feb-2022 15:05

I would say if you've drilled into a reasonable area of gib and your drill doesn't go further, don't push on and force the issue right there. Whatever it is could be to stop you nailing or drilling at that point for a reason. In any case a hole big enough for a scope would take a wall anchor.

insane

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#2874107 24-Feb-2022 15:11

Could it be one of those metal plates you use to protect notched electrical cables or pipe? edit (sorry just read your 40x20cm note)

52mm x 73mm Safeplate - Protect Pipes & Cables

Perhaps as suggested above it's asbestos or some other fibre cement board. They can be seriously hard, enough to blunt a normal twist drill bit.

neb

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#2874109 24-Feb-2022 15:15

If you want to get really fancy, you can get a Walabot, the newer versions are apparently a lot better than the earlier ones, but unless you've got a lot of dodgy construction that needs sorting out it's probably not worth the cost.

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