
There is some risk of water pooling behind the purlins and then getting in around nail holes. The old shingles should help seal things but, yes, there is risk here. I would recommend a quality synthetic underlayment over the old shingles beneath the purlins but even that will not eliminate the small risk.
Hello,
I’m about to start installing a metal roof over shingles and have to install my perlins. My concern is right now we are getting snow and rain mixes and I’m afraid of causing a water leak on exposed perlins waiting to be covered. Is this common for perlins to get rained/snowed on and do they normally leak if so. As of right now roof does not leak and I don’t want to be doing drywall repairs if I don’t have to.
Thanks,
Greg