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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
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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.
9/9/2002
Dura-Loc Roofing Systems, Inc.
9/9/2002