Effective internal wall insulation without taking up too much space?

Snakey

The wall in question is one side of my bathroom, which backs on to a lift shaft. It's cold to the touch, and water vapour from my shower condenses on it in the winter months.

I understand from the internet that cold walls can be insulated effectively by putting up some kind of batten with stuff behind it, but only at a cost of losing about 10cm from the room. My problem is that the wall is less than 3cm from the edge of the door. I don't really fancy having a super-narrow doorway with a folding door.

My initial plan, when I first moved in and was wildly over-optimistic about how easy and quick such things would be, was to "simply" knock the bathroom through into the adjacent toilet, thus allowing me to wall up the bathroom door altogether and then I can "go thick" on the insulation. But this appears to be a massive faff to actually do... I mean, not insurmountable, but in terms of both effort and cost I'm wondering whether I'm using a sledgehammer to crack a nut.

Immediately to the other side of the door is the side of a built-in cupboard thing with the electricity meters and various vertical pipes (my flat is in a ten-floor block), so "just move the door over a bit" doesn't jump out as an easy answer either as I'm not sure I can demolish that.

Anyone got any ideas? Am I even up-to-date in my beliefs about insulation thickness?

Alter_ego

What does the lease say about alterations to the freeholder's building?

Doozergirl

Insulating plasterboard is 37.5mm. That will be plenty enough to stop the wall from being cold.

If you remove what's already on the wall and replace with insulating plasterboard, then hopefully that gain plus the 3cm will be enough. The plasterboard would be dot and dabbed on, so that would add some additional depth though.

If there's architrave on that side of the door then it could also be adjusted slightly to be slimmer, if necessary.

FreeBear

Doozergirl wrote: »

Insulating plasterboard is 37.5mm. That will be plenty enough to stop the wall from being cold.

Different thicknesses are available. If money is no object, the OP could have a look ate Aerogel which is even thinner than PIR insulated plasterboard, but a lot more expensive.
For a shower/bathroom, I'd be more inclined to suggest cement board over the top of PIR (or Aerogel) insulation. Fixed with Dow Insta-Stik (or similar) with a few mechanical fixings for good measure.

Snakey

Thanks guys (and gals)! When you say "what's on the wall already" you mean they take the plaster off to put this stuff on? I hadn't realised that! How thick is the existing plaster likely to be?

I measured 3.4cm from the wall to the bit of the door frame where the latch goes in i.e. where the actual edge of the door would be. (I knocked off 0.5 on the basis that the actual latch has to go in something otherwise the door won't shut... but I suppose that could be gouged out of the panel, since it's only a tiny area.) It's a thin metal frame, due to the construction of the building.

I don't feel like money's no object per se, but I expect I could do quite a bit before it got near the cost of knocking a wall through and bricking up a door and swapping the sink and the bath and levelling the floor and getting the tiling re-done.

The lease says (from memory) landlord consent, planning consent, building consent, listed building consent... with everybody gouging a fee from me, which I guess is fair enough as it needs to be done properly - I don't want my upstairs neighbours unexpectedly joining me in the bath. I'm not too concerned about being refused (other people have had knock-throughs done), it's just a lot of hoops!

It would be an added bonus if hacking off plaster and putting up these boards would not require any such consent.

Doozergirl

I don't believe that it does require consent.

It's maintenance/upgrade more than alteration. Who is ever going to know?

FreeBear

Snakey wrote: »

Thanks guys (and gals)! When you say "what's on the wall already" you mean they take the plaster off to put this stuff on? I hadn't realised that! How thick is the existing plaster likely to be?

It depends.... If it is plasterboard, probably 13-15mm thick. If plastered direct on to the walls, maybe 10mm, maybe 25mm. You could even find that it is a thin smear of microcement or similar that is only 5mm thick. Without drilling a test hole, there is no way of saying for certain. If you are real lucky, the plasterboard might be attached to some pressed steel "studs" with a decent gap behind.

When it comes to the door, one normally has an architrave (or trim) fitted around the door frame, Typically, 30-40mm wide. This covers the transition between wooden door frame and the plastered walls - Removing it may reveal an ugly gap.