How to finish bottom of 2 inch exterior rigid foam
Glock23
| Posted in General Questions on
I will be adding 2 1/2″ of foam over the exterior sheathing. I have searched on this site and others of how to do the exposed bottom of the foam. The common method seems to be bending with a brake, aluminum coil stock in a U shape and fitting the foam into it. Couldn’t that potentially trap moisture?
Would a 2×4 ripped to the proper thickness of the foam + furring strips and screwed to the sill and then the sheets of foam butted to the 2x and then finish with the siding? The 2x could be flashed with a brand name sticky membrane. Snapping a chalk line you would have a nice straight finish to the bottom
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Replies
The best way to finish it is perforated J mold that covers the bottom of the foam as well as the rain screen strapping. This allows for drainage plus ventilation and protects the foam.
Your method also works, I would still put a wide drip edge under the 2x to cover the bottom as well as the siding. You would also need something to protect the vent gaps, this could be coravent or cut up strips of ridge vent material.
There is a perforated formed metal sheet product specifically made for this purpose. Any sheet metal shop could also order perforated sheet to custom make such a product for you. Malcolm, a frequent contributor here, has posted links to the manufacturer of the product he likes to use before (I can’t remember the name of the company unfortunately).
I would recommend using stainless steel for this application and not aluminum. Aluminum tends to rot away fairly quickly when in contact with wet debris outdoors.
Bill
Gentlemen,. Thank you!