I have an old barn that I’m restoring, and being a builder who has been using lime for a good few years now, I’m well aware how important it is for my building to breathe. I have already lime pointed inside and out, and then my plan was to just lime render the inside. However, Building Control are insisting that I tank / waterproof the inside, and seem to have little understanding of how a stone building needs to breathe. Anyway, my question is: is there a breathable tanking solution out there, or if not and I have to use a cement based product, am I best tanking first and then lime rendering over the top of it?
Hi John, thanks for your enquiry.
It is a very difficult situation and one area where the building regulations regularly fail older buildings.
Whilst many tanking treatments claim to be breathable, none will offer the level of moisture movement needed by an older building and we wouldn’t generally recommend tanking unless you are working on say a wall underground.
If you are forced to use tanking, we do manufacture a tanking render – https://cornishlime.co.uk/products/lime-mortars/cornerstone-tanking-render/. This product creates a waterproof render and used a natural cement (modern alternative to roman cement) as opposed to regular cement. Whilst not breathable it does offer an improved flexibility when compared to OPC. We would then recommend this render (and other tanking treatments) is finished with a lime plaster as tanking application can be prone to sweating.
Please let us know if we can be of further help.