Hi Jack,
I've added a link below to explain what I don't have space here to do. But achieving a dry basement is a lot more than just adding rigid under the slab. Building new you have the problem of no history. An existing home in a dry climate with dry soils might qualify for finishing the basement with a high level of confidence, but moist soils in an average climate it becomes risky. Sure, many do it, but some fail dramatically.
I'll let you read and you can follow their other links for a ton more articles, this is a common topic. But a dry basement is a complicated process and most of the effort goed into the ground before the house is built.
Bud
http://buildingscience.com/documents/digests/bsd-103-understanding-basements?full_view=1
I've added a link below to explain what I don't have space here to do. But achieving a dry basement is a lot more than just adding rigid under the slab. Building new you have the problem of no history. An existing home in a dry climate with dry soils might qualify for finishing the basement with a high level of confidence, but moist soils in an average climate it becomes risky. Sure, many do it, but some fail dramatically.
I'll let you read and you can follow their other links for a ton more articles, this is a common topic. But a dry basement is a complicated process and most of the effort goed into the ground before the house is built.
Bud
http://buildingscience.com/documents/digests/bsd-103-understanding-basements?full_view=1
