[SML] : roof question

[Duncan Mahoney]

Dan Sheehan asks:

"our theatre building needs a new roof"

<snip>

I don't think I've seen a shingle roof on a commercial building that big, but then the last time I was in Massachusetts I was not looking at roofs

I think if the plywood, foam, and all the other roof structure stay, and there is a reasonable air seal between the foam sheets, you should be OK with a metal roof over it.

I have worked in a theater with a metal roof that had a 1/2" layer of homasote and a layer of hot mopped roll roofing over it, and nothing below it but framing.  Granted the rain did not hit directly on the metal, but there was less between us and the outside world.  It was never so loud that we had to halt a show when it rained.  On the other hand, my grandparents barn which had a metal roof and nothing below it but "skip sheathing" was quite loud inside when it rained

I would be worried about a metal roof for other reasons.  Your building is big, and the panels will be long (or have seams), which means lots of seasonal expansion and contraction.  The roof will need to be well designed for the movement, or the panels will warp, and/or leak at the seams and fasteners, and there may be some noise as the building heats and cools.  Snow slides well off a metal roof, which may be a blessing or a curse depending on where the "avalanche" lands.

What about hot mopped asphalt or a rubber membrane roof?


Duncan Mahoney
Director of Technical Direction
Associate Professor of Theatre Practice
University of Southern California School of Dramatic Arts