House wrap what is it?

In 1972 the Minnesota building code required a building wrap. For many years prior to the code the homebuilders used 15# tarpaper on all the exterior walls. The code required a building wrap installed between the wall sheathing and the exterior finish of the house from brick, stucco, to siding. I’m not sure what date they came out with the new house wrap made with tyvek or a poly sheet. These new house wraps were good for stopping drafts from wind blowing through the walls.

They designed the material to allow the moisture to pass one way through the tyvek or poly sheet house wrap from the inside of the stud wall cavity to the outside air.

This works great to remove any moisture in the stud cavities as long as the outside temp. Is above 33°F.

Below 32°F the moisture turns to frost and freezes to the back side of the tyvek or poly sheet house wrap, when the temp goes above 32°F it thaws to a liquid no longer vapor.

Now it cannot pass throw the house wrap instead it pools up at each horizontal siding line. This is were the water is new working on both your siding and wall sheathing starting with mold and then rot.

While tarpaper or rosin paper allows the moisture to pass through to the outside. Tarpaper cannot be used behind vinyl siding because it bonds to the siding.

The problem is vinyl siding expands and contracts about 1″. When it moves it loosens the and sometimes it removes the siding.

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