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A valley on our TN farmhouse dormer is leaking. The roof is 5V tin with pre-molded metal valley flashing, but the roof has no solid decking and is just installed over 1x4 strips of wood on 1 ft centers. During particularly heavy rainstorms the water is working its way in over the outer edges of the valley flashing. A contractor has siliconed it 4 times it but the leak just moves further up or down the valley! If we rip it out and re-install it, what type of underlayment do we need to help with the waterproofing (in addition to solid decking)?
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Sometimes, problems like this may actually originate higher up on the roof rather than at the valley.
Anyway, 30-pound felt covered with a slip sheet (red rosin paper) would be appropriate, or any of the newer polymer-based underlayments.
5/21/2004
5/21/2004