Thread: Rain diverter
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Old 08-09-2022, 02:13 PM   #21
DickR
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Quote:
Originally Posted by root1 View Post
Ice & Water Shield under Vinyl Siding will solve a lot of problems.
But, of course, it looks like hell.
That's not such a good idea for a large section of wall, in this climate. That puts a vapor barrier on the outside of the sheathing, which presents a problem in winter. Water vapor diffusing through the inner wall surface (eg. sheetrock) or carried by air leakage from the inside into the wall cavity can condense on the back side of the cold sheathing and be absorbed into the wood. If the water transport rate is low enough, the sheathing will pass the water slowly to the outside world. But that can't happen if I&W is outside the sheathing, so a damp wall cavity can result, unable to dry out, and rot or mold can develop. The only exception to avoiding a peel & stick vapor barrier product over the sheathing might be if closed cell foam were applied in sufficient thickness over the inner side of the sheathing.

Vinyl siding on the outside of a wall actually is fairly good, from a building science point of view, as its very nature provides a vented air gap beneath the outer surface. New vinyl siding products also are quite decent in appearance. Naturally, a WRB (water-resistive-barrier), such as housewrap, should be applied between sheathing and the cladding.

Peel & stick coverings such as I&W Shield have their place above the lower two feet of a vented roof deck, per code, to protect against ice dam damage.
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