Dormer to roof flashing and w flashing on valleys

Guest User
6/26/2009
I am currently rebuilding a shop which collapsed under last winters snow. The dimensions of the building are 26 x 42 feet. I am using 24 inch wide delta ribbed 26 guage ribbed metal that was reclaimed from another project after 10 years of use. There is a 1 foot overhang on the gabled ends giving a total length of 44 feet. The roof trusses are 34 feet at the bottom cord and 9/12 pitch. This gives a 4 foot overhang with a closed soffitt. The top cords are 21.3 feet with a 3 inch gap in the sheeting on each side of the roof peak for ventilation. The roof has two 9 1/2 foot wide dormers beginning 10 feet from the west end of the building. I have w-flashing for the roof valleys of the dormers and sidewall flashing for the dormer wall to roof valley. I want to be certain the flashings are installed correctly and sealed to prevent leaks. The dormers will be sided with 8 1/4 inch hardi-plank cedarmill lap siding. I would like to side the dormers before installing the underlayment and metal roofing if possible. Does the sidewall flashing go under the ribbed metal or over it? How do I best seal the joints beteen the sidewall flashing and the w-flashing in the valleys above the dormer? I am worried about the ribs in the valley leaking if water is blown into them on the southwest side. This is where the worst storms come from. Finally will cutting the upper end (under the vent cap) with a metal cutting circular saw cause a problems or should I use metal sheers? Thanks Tom
Todd Miller
Isaiah Industries, Inc.
6/26/2009
Most manufacturers will call for a butyl tape for sealing. Websites where you can probably doanload instructions for panels similar to yours are www.fabral.com and www.mtlsales.com I suggest cutting only with a shearing action. I do suggest a flashing that goes behind the siding on the dormers.
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