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A Slick Transition from Foundation Insulation to Wall Sheathing

May 03, 2018
Read time: 2 mins

Outside insulation is an efficient way to keep heat in. The devil is in the details like this one

Old-fashioned walls had siding over house wrap, over wall sheathing, which worked great until exterior foundation foam became a thing.

R-15 foundation insulation is required in cold climates, like Minneapolis, and the best way to do it is to the outside. This means about 3 inches of insulation.

You could add a wide flashing to span the foam, but OA Design Build has another way to do it.


Step by step:

  • They begin with waterproofing on the outside of the foundation all the way to the capillary break on top.
  • Next comes the insulation.
  • Cantilevering the framing over the edge of the foundation about ½ in., leaves just enough space above for ZIP R-12 sheathing to flush out with the face of the foam.
  • The joint is then taped against air leaks.
  • The local building department requires a plastic slip sheet below grade, to protect against frost heave.
  • They also require a protective cover, like coil stock, above grade to protect the foundation insulation.

Now they can add a rain screen and siding for a neat transition that keeps the heat where it belongs.


—Michael Anschel owns Otogawa-Anschel Design+Build in Minneapolis, Minnesota



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