Fixing wood to thin outer wall

phil675 · 29 Sep 2021 at 19:49

Hi,

I want to attach a plank of wood to a pebbledash wall for a lean-to. As the inside walls of the house are difficult to drill through, I assumed it would be a pain to go from the outside too. To my surprise the corded non-SDS drill went through quite quickly, there is some soft stuff that goes as long as the drill bit and then another solid wall which must be inside.

So I try one of the thunderbolt screws I had bought anyway and there isn't much for the screw threads to grip into, so they're out. I have some bolts like this:

But if the end that gets pulled up is just in the cavity I'm guessing that won't do much either? What's the best thing to do here? I don't know if plasterboard fixings will be appropriate.

Many thanks.

phil675 · 29 Sep 2021 at 21:18

Doobedoo said:
What was the depth of the outer wall? I’ll guess at 4” so assuming your expansion bolt is also 4” long you’ll be fine.

More like half an inch.

phil675 · 29 Sep 2021 at 22:08

Doobedoo said:
Sorry. You’re saying that the outside wall of your house are only half an inch thick? Are you describing it correctly? Where are you trying to fix a piece of baton too? Pebbledash had me assuming it’s to the outside of your house.

Yes its outside. I drill with a usual diy length 10mm bit, through it goes after a short distance and I hit another wall after a long gap, almost the entire drill bit can get in. There is something in there giving squishy resistance like insulation.

phil675 · 30 Sep 2021 at 10:48

Doobedoo said:
How long is your drill bit?

10-15cm

Abyss said:
You need to better understand the construction of the wall. If it's render sat on insulation or similar you could easily crack the render by putting pressure on it and crushing the insulation. Either when tightening the fixings or from the lean-to pushing against the wall.

This is turning out to be a bit of a pain, the original plan was to put posts by the wall instead but the concrete path there is not very thick either and there is a gap to the soil below, god knows how it hasn't cracked for all this time, but I cant secure a fence post to the ground by the wall either.