Metal roof over asphalt shingles w/ no decking under

Guest User
Bought my first house last summer, inspector failed to mention obvious leaks in roof. It's a 1917 craftsman style house (many valleys). Had a couple of roofing companies do estimates and was told there is one layer of shingles by one company, one layer of asphalt over cedar shakes by another. Both said there is not plywood decking, only boards with 1/2 inch gaps between that shakes were originally attached to. I was thinking about looking into metal roofing if it would eliminate the cost of tear-off and decking. With tax credits I was hoping it would end up being cheaper than the 14,000 I was quoted on asphalt roofing. It's only a 1000 sqft house! Can metal roofing be applied over this and would it end up looking shifty and uneven?
Todd Miller
Isaiah Industries, Inc.
I have seen instances of metal shingles being installed over these situations. In fact, I know of one such roof local to me that has been up 20+ years and is doing great. In that case, the homeowner did save money, and get a very good roof, by doing this. I think that this is a little more difficult to do well with standing seam which is less forgiving when going over uneven surfaces. Now, all that said, building codes typically have a two-roof maximum so that will need to be addressed if you're located in an area with building code in place. Metal roofing, especially lower weight metals like aluminum, will probably add less weight that what the last layer of shingles has lost in terms of granule degradation and oil evaporation. I am not too far from you in western Ohio. Email me direct if you'd like to discuss this further please. [email protected] Every roof situation should be evaluated individually.
Eric Novotny
An informed customer is the Best Customer!
+1 What type of metal were you considering? I, personally, would not go over two layers of roofing. The dump and removal fees will add to the expense but will give you a much more secure installation. Once the roof is peeled back, adding decking usually does not add that significantly to the cost of the project. How many square feet is the roof if the home is 1,000 sq/ft?

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