Insulated slab on grade design
I have several questions about the Insulated slab on grade design. I have seen it done several ways on the internet and really need some advice. A little background on the project.
First this is a timber frame home that will be built in Searsport, Maine. I believe it is in climate 6A and is fairly close to the ocean. It will have 12″ double studded walls with dense pack cellulose blown in the walls. A layer of 1 x 8 pine as the interior sheathing for the roof covered by a vapor barrier. On top of the sheathing will be 12″ I joist running from ridge to overhang and will have dense pack cellulose blown into that cavity and then covered with 1.5″ of polyiso with firing strips attached above to lay down ZIP sheathing for the cool vented outer sheathing of the roof and covered either asphalt shingles or metal roofing.
Now to my question of the slab with apologies for the long prelude.
One method I have seen used is first laying loose flowable fill with 6-8 inches of EPS placed on top. The plumbing pipes are protruding through the EPS and sealed with foam. Then a 15 mill vapor barrier is placed on top of that and sealed with tape. After that ICFs are placed on top to form the continuous footer. After footer has dried, gravel is filled in the open cavity to within 4 inches of the top of the footer and then the slab is poured.
The second method starts with the same first step as above except the plumbing is placed in the gravel above the EPS and appears to go though the ICF before the concrete is poured for the footer and then the slab is poured like above.
I am confused about this and would appreciate anybody’s advice on this and their thoughts
GBA Detail Library
A collection of one thousand construction details organized by climate and house part