Guest User
9/9/2002
I have an older (not sure how old) metal roof on a 7/12 pitch. It is a tin roof made of 16" wide panels crimped together. I am adding a new 2nd story room to the house with a gabled roof(also 7/12 pitch). ___ / \______ Old Roof --/-> \ I / \ <-I-- New Gabled Roof /_________\___I SIDE VIEW /\ / <\-----Old Roof Surface / /\ \ / / <\-\---New gabled end /_/____\_\ FRONT VIEW (Looking at new gabled end) Some contractors have told me that it's "no problem" and others have told me that, in addition to the gabled addition, they will need to replace entire roofing surface where the old roof meets the new gabled construction. The two reasons I was given were 1)that the two dissimilar metals will may react chemically and 2) that a watertight seal can only be ensured if the same metal roofing material is used on either side of the vallies wher the gabled end ties in. I want to tie in a new standing-seam metal roof to the older tin roof. My question is: Are there any issues with tying in two dissimilar metal roofing materials together at the vallies where the two rooves will intersect? My main concern is that I don't want to have to replace such a large portion of my existing roof's surface just to tie into the new addition. Regards, Scott
Allan Reid
Dura-Loc Roofing Systems, Inc.
9/9/2002
You didn't mention if the old roof was coated with tar or paint. There are two conditions to worry about. The first is water run off from one metalic surface on to another and the second is run off from an inert surface on to a galvanized surface. If you have a bare exposed panel I would recommend using Galvalume and to the best of my knowledge a tin bare surface and a Galvalume surface should not have any compatibility issues. If your roof is coated then you should install a prefinished roof of either Galvalume or Galvanized without any problem. As to the tie in, I see no reason why you would have to replace the existing material if it is in good shape however you may have trouble sliding the new valley metal up under with the existing fasteners however you have a good pitch and the rafter lengths on the existing are longer than on your dormer so any water pressure will be greater on the addition side of the valley. You should use painted metal valley to isolate the differant surfaces to be save and fold the valley cut over to seal any exposed steel on both sides. I would try and get an experienced metal roofer, especially one with their own sheet metal shop and always get referances. Good Luck.
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