poly sheeting under metal roof??

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poly sheeting under metal roof??

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Thanks. Let's see if anyone else has input but overall I think this will work.

Todd Miller
2021-02-25 13:04:23.640815

Working on metal roof over and existing agg metal roof! Roof is pretty old and leaky, has good rafters and 1x purlins, agg panels nailed above.

Roof is steep, almost 9:12

Here my plan:

(1) New Pressure Treated rafter sleepers - 2x4 vertically screwed through old roof into old rafters
(2) 6 Mil black poly over sleepers conforming to "valley between sleepers - to keep any water away from old metal roof
(3) New Pressure Treated purlins atop poly screwed into rafter sleepers, possibly w EPDM tape or water & ice shield strips between purlin / rafter intersection, over poly, to seal where screws puncture poly
(4) Agg panel roofing atop purlins
(5) Bottom edges screened (vented)
(6) ridge vent

Poly isn't good for walking! Purlins screwed to sleepers allow roof to be traversed "safely" . Well, that plus safety harness!

Black poly seems to be very durable; even exposed to sunlight , which is main source of degradation, and this won't see sunlight!

THanks!

Will this work? I like the agg panels but they tend to leak. This design leaves existing metal roof as decking, poly to make it waterproof

Bruce kahn
2021-02-24 18:03:05.075300