Installation over wet purlins

Dave Vallett
12/8/2016
I will be installing 29 ga. metal over 2x4 purlins. The application is a maple sugarhouse so it's unheated and uninhabited space. But the purlins had ice and wet snow on them which I've scraped off, though a thin layer remains. I think installing directly on the purlins like this is not a good idea. So I'm thinking of using a moisture barrier: either stapling down building paper strips over the purlins, or, sheathing them with rigid foam. I can't see a problem with the building paper. As for the foam, is there a concern that when I screw the metal down it will compress the foam and result in a poor seal at the screw head? Any other ideas? (Yes, I could just wait until the purlins dry out but it'll likely be quite awhile). thx Dave
Todd Miller
Isaiah Industries, Inc.
12/9/2016
Provided there is some sort of metallic corrosion resistant coating on the back of the panels, and there should be, I am not overly worried about this. If you do use foam or an underlayment, I would suggest that the foam or underlayment be taped at the seams so that moisture does not migrate up into it and then be "trapped" against the back of the metal panels. If this building was inhabited or heated, I would have entirely different advice, by the way.
Guest User
11/6/2017
I'm getting a metal roof installed on my home. It has rained a lot over the last few days. The roofers have some purlin strips installed on the existing roof during this time exposing them to get wet. They have now installed the metal sheeting on them. Should I be concerned of the wet purlins for molding? Will they eventually dry out? I live in PA and its November.
Todd Miller
Isaiah Industries, Inc.
11/6/2017
I would not worry about it. I do not expect this to cause a short nor a long term issue. Thanks for choosing a metal roof!
Eric Novotny
An informed customer is the Best Customer!
11/7/2017
+1 They should have no problem drying out and congrats on the new roof. Post up some pictures when you think about it.
Terry Martorano
12/24/2017
I am having a Metal roof installed on my house in Northern Wisconsin. I have about 12 inches of Snow on the roof now and the roof has two layers of Shingles on it. My installer is going to frame out the roof then put the metal roof on. I asked him what about the snow and he said they shovel it all off. My question is what about all that moisture on the roof from the Snow won't this be a problem? My Guy says they do this all the time and have no problems. Side note my roof is in good condition and does not leak. Please advise so I can either stop him till spring or let it go. Thank you Terry
Todd Miller
Isaiah Industries, Inc.
12/25/2017
This is not at all an uncommon practice and I do not know of any problems resulting from it. Thanks for thinking of metal!
Terry Martorano
12/26/2017
Thank you Todd. I'm going forward with the project after hearing from you. Thank you again for answering my concerns. This really puts my mind at ease. Terry
Jon Sears
3/13/2018

I am having a metal roof installed on my house in Los Angeles. The roofer tore off existing shingles down to the plywood, then installed a layer of new plywood, followed by a 1.5" layer of polyiso rigid insulation (because of my open beam ceilings), then another layer of plywood and then a layer of underlayment. He started installing Berridge Cee-Lock 1-1/2" high standing seam metal roofing over the underlayment yesterday. Looks beautiful. Last night it started raining when only about 1/4 of the roof was covered with metal. This morning when they arrived to continue the job the underlayment and stored metal panels were wet from the rain last night. It is raining and expected to rain off and on throughout the week, so I do not expect there to be much chance for things to thoroughly dry out over the next few days but they want to continue to work as much as possible this week. Is there any problem with the roofer continuing to install metal panels over wet underlayment? Should I have them wait until next week when the rain is over? My concern is that moisture will be trapped causing potential problems (mold, rust etc.) or decreasing the life of the roof. Do you believe it is ok for my roofer to proceed with the installation in the rain and, if so, why? Is there ventilation that will permit that moisture to be eliminated before it could become a problem? Thanks very much for your help and explanation.

Todd Miller
Isaiah Industries, Inc.
3/13/2018

Jon, this is done on a regular basis and, in 35 years, I have yet to see anything bad come of it. Thanks for thinking metallically, by the way!

Jon Sears
3/13/2018

Thanks Todd. Glad to hear that. I appreciate your prompt response and assistance.

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