Re: Slab & Frost heaves?

Posted by Jim G.

In Reply to: Re: Slab & Frost heaves? posted by douglas brown

There is also a section for unheated areas. In this case though, for my part of NH, I would need insulation to go 40" around the slab. That would quadruple the digging I need to do!

The way the insulation works is that it raises the frost line to the surface. The geothermal energy in the earth provides the energy to keep it from freezing. This is what keeps the ground from freezing below 4 ft. Currently the soil is this insulation and you need about 4 ft of it here to keep everything else underneath it from freezing Or you can have 1" of extruded polystyrene. It needs to extend a distance from the slab so that, as you pointed out, energy does not escape from under the slab through the perimeter.

So, I am convinced that the insulation will work but it is over-engineering for this project.