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Yes this old question again. As I read through FHB and JLC forums... There is no one superior way.... and a ton of debate..
Parameters: Building in Southern MN--mixed climate. Putting in a basement I want to finish. As of now I think I'm doing the footings with Fastfoot. I'd like to put down 2" of foam under the slab to help insulate.... I am going to have 4" PVC drain along the exeterior and interior of the footing and run to a sump pit. Will also have powered radon mitigation as radon is all over here. I don't plan to put radiant or anything in as I am putting in a Geothermal-forced air unit. I am putting up an SIP home with and SIP basment package--so I am going the extra mile for moisture control. Soil is a hard loam around here.
Bare with me.... these most common ways I have seen from hours of reading forums.... I have found about 4 main themes of prep people are using...
earth, poly, foam, gravel, slab
earth, foam, poly, gravel, slab
earth, gravel, poly, foam, slab
earth, gravel, foam, poly, slab
I realize foam/poly can be redundant if you tape the seams of the foam--but with our high radon around here..another $100 bucks doesn't bother me.
I have read that people used to think it was cool to put the sand mix over the vapor barrier to help even out drying, but then some say it will stay too wet if the sand was wet and you get curl and vice versa...
So what are the pros opinions on proper prep? What's working for people in the mixed climates--I ask this as I have a lot of shotty concrete guys here and have seen a lot of slabs fail--and some of these contractors change there routine--not based on science--but on how fast and cheap they want to be. I will be pouring this with an old family friend that I trust--but I want to see what others are using before I go after him with my ideas as he is old and set in his ways, but good. He just isn't as dorky or interested in the building science part as me.