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joe71

Is tarpaper ok to use as a sill pan beneath window?

joe71
16 years ago

Hello, I found some dry rot in a window sill. I removed the windows and removed all of the dry rotted wood. It had completely eaten up a board that the windows are supported by, underneath the windows. Directly beneath the dry rotted board I found a metal pan (flashing) sitting on top of another horizontal beam. The beam underneath the flashing is not affected by the dry rot at all. The flashing is partially rusted, although apparently it did a good job of stopping the dry rot. I want to replace the dry rotted wood with pressure treated wood to avoid future dry rot. Since pressure treated lumber is not supposed to touch aluminum (anyone know why?), and since the flashing is partially rusted, what I have done is to put a piece of 30 lb. tar paper directly on top of the partially rusted flashing and then put the pressure treated lumber directly on top of the tar paper, with the window then sitting directly upon the pressure treated board. Does this sound like a good solution? Will the tar paper effectively act as what I think is called a "sill pan" beneath the window? Should I have replaced the rusted sill-pan with a new one, or is the tar paper enough? Thanks.

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