I have an old farmhouse in Piedmont that dates back to the 1960s, and last winter I noticed damp stains on the interior walls, especially in the north-facing corners. I'm not sure whether it's worth doing a surface anti-mold treatment or if I need to work on the foundations. What are the most economical solutions?
The stains in the north corners are almost always capillary rise from the ground, not just condensation moisture, so treating only the surface with anti-mold does nothing! The real problem is that the old brick walls of the farmhouse absorb water from below and capillary rise continues until it evaporates - the economical solution is to create a physical barrier, like injecting silicone resin into the walls from the foundations (it costs less than proper perimeter drainage) or renovate the exterior plaster with water-repellent products and make sure the ground drains well around the base.
If you really want to save money at first, at least improve internal ventilation and surface drainage around the farmhouse - removing soil piled up against the walls and letting water flow away helps a lot, but eventually you'll need a proper barrier anyway if moisture is rising from below!
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