Solid Stone Wall Insulation

[bottler]

I am about to start a full refurb on a Solid Stone Wall Town House from around 1850's. Heating, Electrics, Plumbing, Insulation, New Windows, doors etc... the works.

All advice read around the web is I need to be careful insulating this type of house. As solid stone walls need to breath.

From what I understand, a typical incorrect insulation is using insulated plasterboard internally. With nowhere to go, moisture reaches its dew point on the impermeable material, creating damp patches on the wall.

I can't cover the outside because of aesthetics. Anyway, covering the outside with non-permeable render can prevent internal moisture from escaping, again creating internal damp.

So basically I need to be careful what materials I use to make sure the evaporation will keep dampness levels in the building fabric below the levels at which decay can start to develop. Basically creating a 'breathing building'.

My basic understanding is I can't use run of the mill cavity wall insulation? But surely with all the advances of late there must be a Insulated Plasterboard & process I could use?

Can anyone suggest what approach i should take?

Thank you so much for your advice & help. Truly gratefully appreciated.

Here's a photo of the walls. It's an old house in need of a full refub, but there's no damp. It's good & solid. It's has big thick stone walls: 50-60cm. Currently has no ventilation, i plan to drill vent holes in each room (or the fact that chimneys are in each room, would that suffice?).

 

[StephenStephen]

I'm no expert, but have looked into this for my own home. I eventually went with lime hemp: https://www.lime.org.uk/lime-hemp-plaster-non-hydraulic.html Lovely stuff to work with. There's also these, but I don't know any more about them than is on the site: https://www.lime.org.uk/products/boards-backgrounds-insulation/wood-wool-boards.html https://www.lime.org.uk/products/boards-backgrounds-insulation/wood-fibre-insulation-boards.html
Another intriguing possibility is to go the whole way with hemp, using a mix without sand: http://www.simonjameslewis.com/bristol-hemp-and-lime/

 

[^woody^]

You insulate the inside with whatever you like and then include a vapour barrier if your method includes a cavity or air gaps, and not of it doesn't.

The walls breathe outwards regardless, and that won't concern you or this work.

 

[bottler]

^woody^

Thanks for the reply!

So are you suggesting the fact that i don't have cavity walls... i could proceed as follows:

1) Remove the existing plaster to bring the wall back to the stone work
2) Allow efficient time for the walls to dry out : -/+ 1 week
3) Then use BATTENS to attach the Insulated Plasterboard onto the walls? As DOT & DAB more than likely will attract moisture leading to damp patches?

Is this what i understand?

Thanks

 

[bottler]

I'm no expert, but have looked into this for my own home. I eventually went with lime hemp: https://www.lime.org.uk/lime-hemp-plaster-non-hydraulic.html Lovely stuff to work with. There's also these, but I don't know any more about them than is on the site: https://www.lime.org.uk/products/boards-backgrounds-insulation/wood-wool-boards.html https://www.lime.org.uk/products/boards-backgrounds-insulation/wood-fibre-insulation-boards.html
Another intriguing possibility is to go the whole way with hemp, using a mix without sand: http://www.simonjameslewis.com/bristol-hemp-and-lime/

Thanks StephenStephen !

Interesting indeed. If you have a minute... can i ask you roughly how much more was the lime hemp compared to standard plaster?

 

[StephenStephen]

I can't give a comparison I'm afraid - I never seriously considered gypsum. Also you'd need to compare the cost of lime hemp and then lime finish plaster compared to cost of vapour check, battens, insulation board, gypsum.
The tricky thing was getting enough lime hemp in to justify the delivery cost. I ran out, and only needed a smaller amount to finish, so ended up buying a bale of aubiose from my local agricultural merchant and mixing it myself

 

[endecotp]

One option is to fit 100mm wood fibre batts between studs and then plasterboard. Allow a 25mm gap between insulation and stone.

Historic Scotland have some good case studies about insulating solid stone walls:

https://www.historicenvironment.scot/about-us/what-we-do/conservation/refurbishment-case-studies/

 

[^woody^]

Batten the walls.
Put celotex between the battens with a snug fit and tight against the wall.
Then more celotex across the face of this.
Tape the joints.
Plasterboard and skim

Choose your thickenesses to your requirements.