Flat Roof Design Details
We’re having a new home designed which will have a “flat” roof. The house will be in Portland, OR, Zone 4C.
I’ve read numerous articles here about flat roof design guidelines and pitfalls, including the “ratio rule” for hybrid roof systems. I think the architects’ design (image below) checks all the boxes – R38 cellulose blown in between 12″ TJI joists, R20 min polyiso on top of deck, etc.
Also, they are specifying 1/4″ / 12″ slope, which I like because it creates a flatter roof – but would a slightly higher slope be prudent, since 1/4″ / 12″ is already the code minimum?
Any feedback would be appreciated.
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