I have two problems that I am trying to solve. Number one my foundation is sinking and will have to be piered come spring. I believe this is due to a sprinkler system leak that dumped a lot of water on one corner of home and compromised the soils ability to support foundation. The former owner failed to fill us in on that one. Part of the research I have done has recommended that a membrane be laid down in crawl space under home to help keep moisture in supporting soil under foundation. They recommended this membrane be laid down to about 12″ from footer. The second issue I have wanted to deal with is radon mitigation in same crawl space area. I like the idea of building a subfloor on top of footer and laying membrane down sealing to foundation walls. Part of this install would be a fan to create negative pressure under floor which would be ventilated outdoors. My concern is how do I maintain soil moisture if I am constantly ventilating this area under floor? Or am I over analyzing all of this?