Metal Roof on Top of Shingled Roof

Answered by Jeffrey ~ April 14, 2010 ~ Comments

We need to replace our roof and are considering a metal roof as an option. I have had several different options recommended. 1) Old shingles removed first, 2) Metal roof right over top of existing roof, 3) Metal roof attached to 2 by 4 frame placed over top of existing shingles. Whats the best way to proceed in a climate such as Canaan Valley, WV? Any other suggestions? Have you heard of solar shingles and would they be worth considering?

Andrew B ~ Herndon, Virginia

Jeffrey Anderson

Hi Andrew, I built many homes in Herndon, Virginia about 25 years ago, it's hard to believe it's been that long. Regarding installing a metal roof in Canaan Valley, West Virginia, I personally don't like the thought of installing a metal roof over shingles, even if wood nailers are installed first. I have installed many metal roofs, I have one on my own home, and I think the metal should be supported directly by the roof sheathing. I know that in the old days metal roofs were installed without sheathing, and farm buildings still are, but I like knowing that I have evenly distributed support under the metal. Installing over shingles, or onto wood nailers would be a less expensive installation, so you might want to check with the manufacturer of the metal roofing product you are considering. If they have no problem with it, and it doesn't void the warranty, then you may want to try it.

One of my concerns would be the possibility of the metal rippling under a snow load. Canaan Valley receives a lot of snow most winters, and a metal roof without consistent support below it, could possibly ripple in places from the weight. If your wood nailers are close enough together, it might not be a problem, and heavy gauge metal might be better if you decide to go ahead and install over the shingles.

Solar shingles seem to be a good product, and there are also metal roofs which are now Energy Star Rated due to their reflective ability. There are metal roof manufacturers which now offer solar collector panels with their roof systems, and I think that might be a great idea for a metal roof in Canaan Valley. I know it can get very cold over there in January and February.

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