Questions about refoofing with metal.


Old 04-08-14, 04:57 PM
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Questions about refoofing with metal.

I planning to install a metal roof (26 Gauge, 5 rib) over a single layer of degraded shingles this summer and have a few questions I'm hoping to get advice on.

1. How much screw penetration into the rafters is necessary for proper installation of the purlins over the shingles?

2. I'm planning on slightly less than the 24" purlin spacing the manufacturer recommends. In the real world will that be sufficient for a roof with an 8/12 pitch?

3. The manufacturer recommends synthetic underlayment over the shingles and under the purlins. It seems unecessary and I've gotten a lot of conflicting advice on this so far. What's the experience on this in the field?

Thanks in advance...
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Old 04-09-14, 05:15 AM
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Welcome to the forums!

I'm not a roofer but I have installed a few metal roofs.

#1 - probably an inch or so, hopefully one of the others will chime in that know for sure
#2 - IMO that's too far apart, I'd go 12"-16"
#3 - I wouldn't think it's needed since you are installing the metal above shingles, it is needed if you are installing the metal directly over plywood.

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