r/DIYUK • u/Beast_Chips • 17h ago

Building Wall Insulation

Recently discovered we have a void in the wall cavity between the outer brick wall and the inner plasterboard wall, upstairs and downstairs. I can't get in to see properly without making a much bigger hole, but my dad (he lives in an identical house up the street) reckons if it ever actually had any insulation, it has either sunk right down to the bottom, or has just disintegrated over the years.

What's the best (most balanced in terms of cost Vs effort Vs effectiveness) way I can put cavity insulation in here? Ideally I'd like something less invasive (expanding foam or something?) where I can just "squirt it in" so I don't need to do a huge amount of wall repair afterwards, but obviously if invasive is the only option I can replace the boards etc, I'd just prefer not to.

Surely someone has invented some amazing modern product that is both easy, cheap and effective? 😅

3 Upvotes

100% Upvoted

12 comments sorted by

2

u/ForsakenTomorrow7880 16h ago

Sorry I can't help, but commenting so I can see responses too

2

u/GordonLivingstone 15h ago

It is going to depend greatly on how the house has actually been built.

Sounds from your description like a timber frame house which would have insulation and a vapour barrier (polythene sheet) between an outer plywood skin and the plasterboard. The brick wall would then be built around that - with a gap to stop damp getting across.

All sorts of variations are however possible.

Don't just inject foam or other insulation without knowing exactly where it is going. Could cause all sorts of problems with damp and then be very expensive to rectify.

It ought to be possible for someone to look behind the wall using an endoscope type camera to see exactly what is happening.

A competent builder who knows the type of house should also be able to advise. Don't just hire someone who promises to fix all problems by injecting or spraying foam.

1

u/Beast_Chips 15h ago

The house was built in the 20s, classic North East brick end terrace. I don't think it has anything like a plastic vapour barrier etc, just literally plasterboard, studs for the boards then brick behind it. Upon further inspection it seems to have the remains of classic wool type insulation, so I assume at some point that was the only thing between the boards and the brick.

Obviously I'll get a builder if I absolutely have to - I get an electrician for most electrical stuff and a gas engineer for gas stuff - but from the amount of absolute clowns around I'd prefer to do this sort of stuff myself if it is the sort of job that's achievable safety for a DIYer. Once bitten, twice shy with builders unfortunately.

It ought to be possible for someone to look behind the wall using an endoscope type camera to see exactly what is happening.

What would I be looking for?

1

u/HugoNebula2024 14h ago

A 1920s house would be either 9" solid brick or a brick inner & outer cavity wall.

Could it be a dry-lined wall (plasterboard and insulation between timber battens), or plasterboard on dabs (a thin 10mm cavity), both applied onto the inner leaf?

1

u/Beast_Chips 13h ago

I'm fairly sure it's 2 brick layers with a cavity in-between. I'll check the next part...

1

u/DanLikesFood Novice 13h ago

There's some cheap endoscope cameras on Amazon. I bought one for £16. Not amazing but I inspected some awkward places and even helped me find the leak in my washing machine.

2

u/banxy85 14h ago

Have you got any damp? A 1920s house likely doesn't have a cavity wall and therefore adding any insulation internally can be dodgy

2

u/Beast_Chips 13h ago

We do get a little bit of damp in other areas, but not on this particular wall. This was a major concern and why I'd like to get it right rather than just throwing any old insulation in there. I assume I'd have to use some kind of barrier?

2

u/banxy85 13h ago

Does your dad in an identical house get damp? It's really problematic trying to internally insulate a solid wall house. The fact you don't get damp here possibly indicates that you shouldn't be nsulating

2

u/Beast_Chips 13h ago

So am I a bit stuck here then, short of getting in specialists to insulate between the brick layers? I've also considered adding some kind of dense board insulation on top of the plaster board and replastering, but then obviously I need to change skirtings etc to accommodate the thicker walls on the inside.

1

u/banxy85 13h ago

Depends if you have a cavity wall or not. They were very uncommon in the 1920s but did exist.

If it's not a cavity wall then the only good option is to clad externally

1

u/inside12volts 2h ago

How cold is the house? So much of an issue that it’s worth a the extra work?