Stonework preservation

A common mistake many people make when renovating a stone built property is to use cement based renders and mortars. Raking out the lime mortar and re-pointing with sand/cement mortar or even worse rendering the stone with a sand/cement render will literally prevent the stonework from breathing. Likewise rendering the internal surfaces of the external walls with cement based renders and plaster will cause decay of the stonework. Literally the walls will weaken, crumble eventually collapse.

The tradesman of the past knew a thing or two when building stone properties. Stonework needs to breath otherwise trapped moisture together with the extremes of weather in the form of freezing and thawing will permanently weaken the stone. Lime based mortars and renders allow the passage of moisture through the wall construction. and allow the surface to dry out. Poor choice of materials including vinyl based emulsion paints result in the formation of salt stains and paint flaking on internal surfaces.

So use lime mortars and renders if you want to preserve stonework. Lime based paints must be used on the walls. You may get the odd damp patch here and there in the winter months but these usually dry out with minimal damage to the decorated surface. At worst patch painting of the wall with spare lime based paint is all that will be required. Better this than rebuilding the entire wall.

A really good site that goes into greater detail and should be consulted in all matters stone wall damp issues is http://www.heritage-house.org/damp.html