I was doing some quick research on the web to find the best ways to redo the facade of my new/old stone house, and currently I'm almost in tears after learning few things. Thing is simple, but extremely problematic - I renovated old (about 400 years) stone house this year - small one about 80 sqm footprint - just ground floor As house walls are partially bellow the ground level I consulted several 'specialists' in order to find the best way to stop water penetrating it. Following some of those advices I ended up rendering all but one of it's old stone walls on the interiour with just OPC/sand render - no lime at all. It's done as base layer for additional cement based water insulation. Just tonight, 6 months after I moved in my newly finished interior (insulation seems to be holding great for 6 months now), I learned that use of OPC like that could be devastating to my home. Just to give you few basics - masonry is double layer - about 80 cm thick in total, mostly limestone, originaly built with lime/sand based mortar. What to do, and how urgently it needs to be done in order not to ruin what generations before me maintained and cherished? I would appreciate something less violent and something giving me some time - as I just moved in and that's my only home. Opinions?