Guest User
2/25/2002
I am in the process of putting a metal roof onto my house. I have a dormer that is recessed one foot off of the edge of the bottom roof line. The dormer pitch is 7/12 and the main roof is 4/12. My problem is where the dormer end rafter meets the main roof line. What is the best way to make sure that I get a leak proof seal there? I am using V-crimpped valley flashing and have explored different bending options, but nothing gave me a confident leak proof seal. Any information would help greatly. Thanks.
Allan Reid
Dura-Loc Roofing Systems, Inc.
2/27/2002
A valley works best in equal pitch intersections as the water run off from each side meets and takes the speed out5 of the flow. In this situation you will have water running twice as fast off the dormer than the main roof. This is issue is relative to the rafter length on the dormer and the rafter length on the main roof. if as an example you had a 30' rafter feeding water down the main roof and a 4'rafter on the dormer the volume on the lower pitch could power up under the roofing on the dormer. In these instances we recommend a triple W valley metal that profides additional diverters for the water on each side. Ideally you would remove the existing roof metal to tie in and put a self sealing ice and water shield up the valley and the wider the better. If you are unable to remove the old metal you should still try and slide the ice and water sheild up under the existing roof as far as the valley metal and you can still peal and stick the xposed side. If tis is unsuccessful you can order a 36" wide valley and stick the ice and water shiel to the back before you slide it in. This way and fasteners are that penetrate are self sealing. Good luck.
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