Best way to insulate a cavity wall where outer wall is holey

[elfinblues]

Hi everyone.

I'm hoping that someone might be able to suggest the best way forward for me to insulate some tricky walls in our ground floor extension.

We live in a mid-terrace house, and we want to improve the heat retention of the single-storey ground floor extension that previous owners built onto the back of our house. All the houses in our terrace have had similar extensions built, and ours was apparently the last to be done. And because the side walls of the extensions are all so close together, I presume that both the inner and outer walls of ours were built from the inside. (The gaps between our extension and those to either side are at best 12-14 inches wide. It might be possible to squeeze down one of them, but the other gap is too small for anyone to get into.)

Our main problem is that our extension is so bitterly cold through the winter as to be unusable, so we want to better insulate the walls and ceilings, and to carpet the floors. Our problem with insulating the walls is that from the small amount of the outer wall that I can see, the mortar between the concrete blocks is missing here and there. I can't see how extensive the problem is without attempting to squeeze myself into those gaps, which might not be do-able anyway. So cavity wall insulation is out. Is there a safe way - without creating problems with condensation - to insulate the walls from inside - i.e. plasterboards backed with insulation boards? Would this work?

And if anyone has any additional ideas about how to tackle repointing those hard-to-access outer walls that doesn't involve demolishing the interior ones to get to them, I'd be really glad to hear them!

Thanks very much in advance for any help that anyone can give.

Best wishes,
Steve

 

[IanNE]

Get the insulation blown in from the inside leaf of bricks.

 

[kbdiy]

Assuming the walls are cavity, I think this is probably the best option you have although it would mean some disruption and redecorating inside. I wouldn't be too concerned about the missing mortar, it isn't likely to go full depth so cavity insulation would be ok.

Before you go too far are you absolutely certain the walls are cavity and not solid block? You don't mention when the extension was built and it might not be cavity. Just a thought?

 

[elfinblues]

The extension was certainly planned in 1998 (I have seen the plans drawn up then) so I presume it was built that same year or 1999. No, I am not 100% sure it is cavity but the walls are thick, so I would assume so. They are dry lined on the inside.

I'm not worried about disruption inside as we are going to redo the ceilings to get more insulation up inside, and doing other changes too, s there will already be some replastering etc. to do.