Roofing Metal Roof Installation

Published on September 7th, 2016 | by Henri

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Installing standing-seam roof

Q.  We have recently gotten several estimates on what it would cost to have a standing seam roof placed on our house. Most estimates included the cost of stripping the “architectural” shingles off first and then putting on either a 24 or 26 gauge metal roof on.

One roofer, who has been doing standing seam roofs for 20 years, said that it was not necessary to remove the old shingles, that he would just re-roof it with a metal roof right over them and of course the estimate was much lower than the others, as there would be less work involved.

Although this information came from a well-known, recommended and experienced roofer, we are wary of what may be a short cut. If he’s right, we’d save a good bit of money. Do you have an opinion about whether it matters or not to leave the old shingles on? Also, does one way over the other make a difference whether you would choose 24 or 26 gauge?

A.  If the old shingles are not removed, the metal roof will telegraph them after being exposed to the sun, and the roof will look pretty bad.

If the rafters can structurally take it, a layer of sheathing-grade plywood can be nailed over the old shingles to avoid having to remove and dispose of them as required by local governments.

You should also insist on the heavier 24-gauge metal, as it will be a lot quieter under windy conditions. Both 24-gauge and 26-gauge metal roofs will oil-can when the wind blows hard, but 26-gauge metal will not only do so a lot more, but it will also sound like a freight train is running on your roof.

You should also insist on having all seams double-locked and sealed with polyurethane caulking and the bottom of the seams at the eaves be protected by a metal flap folded over and caulked. Failure to do so has resulted in sheathing and fascia boards rotting over time from rain penetration on windy days. Rafter tails have also been affected. Experienced standing seam roofers know how to do that.

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