|Posted on Saturday, January 13, 2007 - 06:21 pm: ||
Most of the valleys we install are parallel, not tapered. We only install tapered valleys in order to match an existing valley or upon request. Tapering the valleys (widening them nearer the bottom) is primarily a stylistic measure and not really much of a functional one. 99.9% of the valleys we have replaced over the years (miles of them, literally), have been parallel and they have functioned well on every type and size of building (the longest valleys we have replaced to date have been 42'). Here in north western PA we receive more precipitation that either Seattle or Portland, Oregon, and we have the severe freeze thaw issues that compound the effects of weather on slate roofs. So we have a good place to test slate roof systems and the ones that are 120 years old and still functioning well have parallel valleys. We install our valleys with a standard 6" exposure using 16" stock in most cases. On larger buildings (churches, institutions) we often install a 8" valley exposure, using 18" stock. The idea is to have 5" under the slate. You can have more, but then you're just nailing through it with the slate nails. 5" underlap is all you need in most cases. Of course, we will install any size valley and any exposure to match the existing conditions if necessary.
|Posted on Thursday, January 11, 2007 - 10:29 pm: ||
Traditional roofing at times does call for tapered valleys,good roofing practice,since the volume of water increases as it flows towards the bottom of the valley...Uniform valleys work just fine,I would say over 95% of the valleys we have installed or replaced have been uniform type(even spacing 6" to 8" wide -3" to 4" from center up each side) If installed properly a warranted installation should be no problem,especially since this is what you would prefer...At times a tapered or W style valley should be installed to help eleviate excessive water flow from large roof areas or intersections of different roof pitches ect..
|Posted on Thursday, January 11, 2007 - 05:47 pm: ||
architect wants a uniform dimension top to bottom, installer (on roof) says fine no problem, do it all the time, Owner of Roofing company (on ground) cannot do, must be tapered, or i will not warranty installation!
What is the downside or maintaining even spacing up the vally, looks so much better!!