Rendering a medieval building

[cve60069]

Hello.

I have recently moved to Devon and two of my first jobs is to restore cottages with walls made of Cob. Reading the forum, I have a good idea of what to do, materials, mixes, application, drying, etc.; but I am concerned about waterproofing the internals, particularly as the walls have to breathe.

Please see photo. The bottom metre is stone, the stuff above is Cob. No DPC. I will waterproof-cement-render the stone and lime-mortar-render to the Cob, tape the joint between the render and lime, and apply a lime-plaster finish-coat over the whole. Externally, I apply a lime-slurry only, not a waterproof-render.

Would this work and will the external slurry require a top-coat of something (paint) to make waterproof?

Cheers.

 

[Capital spread]

You have a medieval building and you want to put a very modern waterproof sand & cement render on stone ? why not do the whole thing in lime !

 

[cve60069]

I need to tank the bottom metre of wall. Is it possible to make the lime-mortar waterproof?

 

[gooner59]

yes but why would you need to tank the bottom!? in a wall that is designed to breath ! you will create a problem !.......

 

[cve60069]

If you look at the interior photo. That is damp you can see at the base of the wall. My damp-meter hit max. I've swept up the rotten timber damaged through the damp. I intend to dig up the floor, lay a membrane and tank the stone. Am I wrong?

 

[Capital spread]

If you limecrete the floor and lime render the stone you will allow the structure to breathe. Any mositure will be absorbed by the lime and will evaporate when the temperture rises. Building must have ventilation. Just finished a small stone barn in France built of Red Granite stones the outside was pointed with lime and the inside was lime rendered and finished with clay plaster.
When I was there in October it was cold with heavy rain,the barn had no heating on but was dry and not at all damp.

 

[cve60069]

Cheers. I will give lime-plaster a go.

 

[lucius]

Dont put in a concrete floor and membrane it will force any damp into the walls

 

[seanlar]

they are right also check the ground levels outside always a reason for damp . www plasterinlime.co.uk

 

[Fatarm]

Who is. www plasterinlime.co.uk mate

 

[seanlar]

a new member

 

[Fatarm]

Oh right, it's you?:rolleyes)

 

[earthy]

Hello all, I'm a new member and have only just seen this thread.
We work with cob in Devon so please contact me if you want to discuss cob or lime etc., if I can't help, I could direct you to someone who can.
That said, I hope you haven't undertaken the works as you described, they are totally inappropriate for a traditionally constructed building, especially one constructed of cob.

 

[bubbles65]

Welcome along.
How do you do it Earthy?