I recently purchased an old home (we don't have a date but at least as old as the 1870's) with a stone foundation. It is located midway up a hill side in the mid-atlantic region (zone 4). The home has modest radon levels (right around the legal limit of 4, on average). Originally the home had a side lot which was later developed and sold off...this lot is directly uphill (so little ability to manage landscaping). Over the years a rat slab was added that shows signs of heaving and the basement always has wet spots (it is likely the soil has high clay content) both where there is now exposed dirt and where the concrete is damaged. The basement also originally had five windows. three windows were sealed (in concrete) when the exterior grade was raised and a fourth was lost to a rear addition so ventilation is sub par. the stone wall is covered in parging. The radon specialist said due to the grade issues (concrete sealing in the basement) it would be difficult to install a system and more to the point, he does not think a system is necessary, just an intact concrete slab. The other goal is to reduce moisture. I have no intent on making it a living space but we do have mold issues during the wet months. With the dual goals of reducing moisture (most of which seems to rise from the floor) and radon, should I work on restoring some ventilation or just install a slab...and if the latter, proposals have been for a 2 inch slab (on top of what can be repaired) or full excavation with three inches of rock and four inches of concrete (with or without a pump). the basement does not have flooding issues, just modest radon and humidity issues.