We are planning to retrofit out 1987 saltbox in VT with radiant
heat. To make installation easier and cut down on the water vapor
in the house, we plan to pour a concrete floor in the crawlspace.
I am wondering how we should prepare for the concrete pour.
We ran into ledge at 4 ft when building our house, hence the
crawlspace. The excavator recommended we put down some poly and
cover it with 4-6 in. sand. Big mistake, our house is halfway
down a hill and in the spring the sand becomes saturated even
though we have done everything except put in a French drain above
the house. (We have footing and surface drains.)
Before pouring concrete should we put down another vapor barrier?
What about insulation? Also should we put in drains and a sump
pump? This crawlspace is only wet in the spring. It is dry the
rest of the year.
Can someone point me to a publication or an article for doing
this project?
Thanks for your help!
Saltbox
Replies
Around here (northeast of VT by about 10 hr drive), the standard for under floors (basements, slabs, etc) is to put down 1.5" foam, 4 ft wide, on the gravel, so you have a 4ft wide strip of foam all around the perimeter of the floor; cover with 6 mil poly, that goes up the wall where it can be sealed to the wall vapour barrier. Put the floor on top of that.
Apparently, the greatest heat loss through the floor is at a point about 18" in from the perimeter wall. You can insulate the whole floor if you prefer, but the biggest bang for the buck is the outermost 4 ft.