Who's in the know here about how you put a metal roof over shingles?
Answered: 2019-07-29 19:27:55
Here's my advice: Put some l 1x4 Purlins down over the shingles before installing a metal roof. This is the most common way to install a metal roof. As long as the plywood under the shingle roof is in good condition, this way can work well.
It's a simple task. You just have to make sure that the shingles are in good condition. If you must, go up to your loft and ensure that, before you do anything. The metal roofing is nice and lightweight, get a good underlay, and just lay the sheets over that. Make sure it's lined up right and screw it in.
Apply an approved underlayment right over the old shingle roof. The best part of doing it this way is that it is the fastest way to install a new metal roof over a shingle roof. This is the minimum that needs to be done. Some people think that they can just install the metal roofing right over the old shingles roof without any barrier in between, but this is not recommended at all. Cos when the metal heats up and expands or cools down and contracts, it moves on the roof. What ends up happening is that the shingles act much like sandpaper to the back of the metal roofing, gradually scraping away the back and exposing the bare steel.
I would actually remove the old shingles before installing the new metal roof. That way is that you can see if there is any rotten plywood that needs to be replaced before installing the new roof. You can walk around the roof and feel for “soft” spots, and that's where it might be rotten or deteriorating plywood. You will have a much stronger metal roof if it is being installed into good wood as opposed to rotten wood.
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