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Ground Roof on FPSF

stephenr | Posted in General Questions on


I am working out the details on my fpsf, zone 6 coastal maine.  I have 4 feet of wing insulation all the way around and I am using type II EPS.  There will be a 4 inch footing drain exterior of the grade beams as well.  The wing insulation will be pitched out slightly to shed water and it will essentially rest on the 4 inch pipe at the grade beam.  Is it necessary to top the EPS with EPDM to promote water drainage?  There will be 1 foot of soil over the EPS and i have 2 foot overhangs.  Also, should I seal the connection between the vertical EPS on the exterior face of the grade beam and the wing insulation with wigluv?  Hoping to avoid fentrim due to cost.



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  1. Expert Member
    Michael Maines | | #1

    It depends... the building code requires foam frost wings to be protected by something rigid if less than 12" below grade, not that anyone enforces that particular rule. If you install a layer of clay or clay-loam mix at grade, that will block a lot of stormwater from reaching the foam, vs. installing a drip course of 3-4" crushed stone will direct stormwater downward. If your site is on a slope with well-drained soil, and you have solid PVC footing drains to open air, that is a much more forgiving situation than being on a low, wet site or on clay. Large roof overhangs will direct a lot of water away from the house--unless you live in a place where the wind blows when it's raining, such as coastal Maine--vs. a "monopoly house" with no overhangs. If you have gutters (and no trees near the house, and/or really effective gutter covers, if there is such a thing) and the downspouts lead to a drainage system, that's more forgiving than relying on a ground gutter.

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