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Concrete porch meets foundation insulation – detail

climb_on | Posted in Green Building Techniques on

We are in Minnesota (Zone 6a). 2200 sq/ft single level, slab on grade.

Can anyone explain, or point me to a detail that shows a good way for a patio, porch or garage apron to meet the perimeter insulation of a slab foundation? I plan on 4″ (r-20) of perimeter insulation.

Is it as simple as removing the foundation’s 4″ of perimeter insulation the thickness of the patio slab and replace with 1/2″ expansion material?

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  1. GBA Editor
    Martin Holladay | | #1

    The above-grade portion of the vertical perimeter insulation will be protected with metal flashing, stucco, or pressure-treated plywood. The patio will abut this protective layer. The 1/2-inch expansion material is probably a good idea, but I wouldn't remove the perimeter insulation or the protective layer (the metal flashing, stucco, or pressure-treated plywood).

  2. climb_on | | #2

    Of course it will (head slap). But what about at the garage apron in front of the doors? The garage foundation is being treated the same as the rest of house since it will be heated, although, only to about 40-45 in the winter. Also, do you have a favorite protective product/material for the foam?

  3. GBA Editor
    Martin Holladay | | #3

    There is no perfect way to detail the top of the rigid foam near the garage door.

    Here is a method that's about as good as any I know: Cut back the vertical rigid foam so that it is 1.5 inch lower than the slab elevation. Take a pressure-treated 2x6 and rip it down to 4 inches. Carefully glue the pressure-treated strip to the top of your 4 inches of rigid foam with foam-compatible construction adhesive.

    Not a perfect solution, but it works.

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