We have been trying to rectify penetrating damp in our building for many years and at much expense, we have repaired the roof, repointed with lime outside and rendered with lime inside and painted with lime wash/Eathborn clay paint and have now faced the fact that since it sits up high facing the prevailing conditions the wall (victorian granite/killas with rubble in fill) was not constructed thick enough and the stone is not of good enough quality or type and cannot therefore deal with prevailing wind blown rain….the last few winters have not helped! We are considering either bag rubbing or lime rendering, having taken off inappropriate dry lining inside I do not wish to dry line again since even with appropriate boarding and ventilation I still dont think it would deal with the kind of moisture levels. Tile hanging is not an option due to window detailing. My gut feeling is that bag rubbing would not give us the depth required to deal with the conditions and we’d still be experiencing wet and black mouldy walls (the room is a bedroom and uninhabitable) and so feel that external lime rendering is our only hope, three coats or four coats, NLH 3.5 with Beeck or similar paint!? Any advice/hope very gratefully received!
From everything you have described, a render would be much more appropriate than a bag rub finish and will provide a greater level of protection.
t is difficult to make specific comments on materials without seeing the building, is there any way you could send us photos of the external elevations and then we discuss the potential solutions in more detail. Please email any images to firstname.lastname@example.org, many thanks