If you go right down you could get zero VAT on the rebuild

What level of insulation are you aiming for?

I had the opportunity to buy a Scottish stone cottage (1½ story croft house near Tongue which I was renting at the time) and decided against because I couldn't see a convincing way of insulating it well. External wall insulation didn't seem to make sense as the thick walls would cold-bridge straight into the ground. Extending the external insulation downwards wouldn't have helped as the water table was too high even after some serious drainage was added behind the house.

I'm not sure that anybody can come up with a good way of doing serious internal wall insulation on a house of this type, it seems to me to be too difficult to generalize on what moisture will do and too difficult to measure what's happening in a particular house. Also, with houses of this type significant internal insulation may well have issues with room size or ceiling height.

I think it's quite possible to put some useful insulation on an existing stone wall in some cases, either externally or internally depending on circumstances, but that if you want a really cosy house and you can replace the walls then doing so would be the lowest risk option and give the best results.

Posted By: 1980scotlandHi,

On my stone property I am converting, one of the gable walls was required to be rebuilt due to its condition. Previous owner rebuilt, by making stone outer wall with blockwork inner wall, with 50mm air gap. The other walls are in good enough condition to just need repointing. However, I wondered from an insulation point of view, and to avoid condensation/damp, if I should just knock down and rebuild other walls (I guess I might need to get PP to do this but just asking for advice)?

I'm suspecting it isn't a massive house but even then it is a massive amount of work and cost to knock down 3 walls and rebuild them when they are structurally sound. Building stone walls is not the same as throwing up bricks or blocks. Then trying to avoid the good gable falling down as well.... If they are sound, repoint and insulate internally to sort out condensation. Sort out the ground outside to fix any damp wall issues (also repointing will help depending on where the damp is). No planning issues with this.

Thanks for responses.

Chris - yes, quite similar. The reason I am now unsure what to do is that on the wall previous owner rebuilt, rubble wall was removed, then single course of granite stone for external wall, 50mm air gap, then blockwork wall internally. This will still need to be insulated inernally. Wall was rebuilt using cement mortar, effectively as if you were building a new building, but not quite. Seems a lot of work when other walls are sound, so post was just to get a feel for what others have done, to try and get a bit of objectivity, and also if mixing and matching poses any issues!

Posted By: Phil.Chaddah-DukeI would say get planning and knock down just from a VAT perspective, we wish we'd knocked ours completely down, wasn't stone walls but would saved a lot of dosh and avoided lots of compromises, never seems worth it looking back, for the sake of a few walls!

Planning will be weeks if not months of delay, VAT savings?! The cost of rebuilding a stone wall is massive!!! They do not go up quickly, and require skilled labour which is not easy to find. Completely different ballgame than block or brickwork. Plus you no doubt find there are no foundations and the like..... and of course a new roof.

The whole lot can be insulated internally, doesn't matter about the mismatch of walls, gut the inside, timber studwork to get walls straight and plumb then insulate between/in front of studs. No delays as building remains weathertight, everything off the shelf, no specialist labour.