Can you "roof over" an asphalt roof with a metal roof on a manufactured home?

Hey everyone, I’ve read somewhere that you can only have one layer of roof on a mobile home, but I’ve seen a ton of material about how you can roof over a mobile home roof (provided its not flat) by adding a metal roof. The roof I inspected today had a layer of shingles underneath a metal roof. Is this allowable?

Thanks!

Someone “can” do whatever they want, whether or not its proper is another story. Regardless of the structure type, adding a second layer of roofing is generally viewed as a poor practice. The preferred practice is to replace a roof rather than just cover it up.

If it had shingles, it could have easily been torn off and re-shingled.

Around here, 90% of most “aged” manufactured homes have a “roof-over”, some sort of metal roof (pan, 5V, standing seam, etc.) installed over the existing metal roof. Periodically, a shingle roof is installed in place of an aged metal roof on one of these M/H’s.

Most metal roofing manufacturers have specific requirements for how to install their product, including placing them over another material, so researching the install specs can help.

Because metal roofs expand and contract at a rate greater than that of asphalt shingles, the shingle granules will abrade the underside of the metal over time. Makes no difference what type of building it’s on.

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Very true Kenton, and that is why a slip sheet is required on top of the shingles before the metal gets installed. For cheaper corrugated metal roof, it is best to install over furring strips attached on top of the shingles. That is if your local codes allow.

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Thanks everyone for the feedback. It’s a 28 year old home (1992) and my biggest concern was with the weight. I had read somewhere that it was bad to have two roof coverings due to the weight, but I can’t find that info anywhere. So, my suspicion is that it’s ok, if it’s done properly. Thanks for the input!

Yes, it is bad, but building codes will allow 2 roof coverings, and it is always best to check with your local jurisdiction on what they allow.

Problem being is building codes don’t apply to manufacture homes. building codes would require an 18 to 24-in center and the trusses and approximately half an inch on the sheathing. Manufacture homes are 3/8 on the sheathing and up to 36 in on the trusses. Manufactured homes are not allowed a second layer, only exception is a sealer coat. I’m trying to find the actual hub letter that calls that out, if anybody knows of it I could use a copy. Lost my hard drive and some of my data and trying to rebuild my library. Thank you

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