Renovating a stone walled house

[Carnmore]

The house is single storey and circa 100 years old with solid stone and lime mortar unplastered walls about 450mm thick.

It consists of just two existing external walls (40m2) , a party wall, an extension to be rebuilt at the back and a roof to be renovated (slates removed, timbers repaired where necessary, felted, new roof battens and reslated using original slates.

The finished floor has been poured - rigid insulation board and cement.

For insulating the external walls, my architect and builder are recommending installing a steel stud wall to create an air gap and then dry lining with insulated plasterboard.

I'm on a budget and the cheapest method is insulated plasterboard as described above which would cost about €1k. Despite this cost and advice, I'm concerned about the breathability of the walls.

I would also prefer to use non-toxic materials where possible.

Would Calsitherm or Gutex be a better option or is insulated plasterboard okay?

The cost of Calsitherm including a lime scratch coat would be circa €10k..

Thanks in advance for any advice re this or in general.

 

[Notch7]

What concern do you have about the breathsbility of the walls?

Do you mean the stone wall too breathable or the plasterboard wall not enough?

If it was me, Id go for an air cavity a metal stud walling.

You lucky bugger living in France what part?

 

[Carnmore]

What concern do you have about the breathsbility of the walls?

Do you mean the stone wall too breathable or the plasterboard wall not enough?

If it was me, Id go for an air cavity a metal stud walling.

You lucky bugger living in France what part?

I mean the wall is breathable but insulated plasterboard is not.

I'm in Ireland

 

[Notch7]

'm in Ireland

Oops I assumed.....didnt look at the little flag!

Given the damp location, I would say your safest option is a clear cavity.

You might be best to seek local advice though, since local weather and local experience of construction may provide more insight into the most successful methods.

 

[StephenStephen]

I used lime hemp plaster - nice stuff to work with, but probably expensive if you get someone else to do it, rather than doing it yourself (I'd not done any plastering before)

 

[Footsoldier888]

I mean the wall is breathable but insulated plasterboard is not.

I'm in Ireland

Perhaps this stud wall will have a vapour barrier behind the plasterboard such as you get on a timber frame house, allowing the moisture to pass both ways.