Installation over wet purlins

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Installation over wet purlins

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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.
Guest User
2017-11-06 19:02:50.000000
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.
Todd Miller
2016-12-09 05:12:21.000000
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!
Todd Miller
2017-11-06 19:22:06.000000
This is not at all an uncommon practice and I do not know of any problems resulting from it. Thanks for thinking of metal!
Todd Miller
2017-12-25 07:35:59.000000

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!

Todd Miller
2018-03-13 19:19:22.392957

In your exact case, I would recommend that he install a quality breathable underlayment on the roof after he removes the current material. A breathable will allow the decking to dry out but yet still protect it from further moisture. The product I am most familiar with is Cromar VENT3 but there are others as well.

Todd Miller
2018-11-25 10:55:24.693250
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
Dave Vallett
2016-12-08 21:10:48.000000
+1 They should have no problem drying out and congrats on the new roof. Post up some pictures when you think about it.
Eric Novotny
2017-11-07 06:01:58.000000
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
Terry Martorano
2017-12-24 13:16:31.000000
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
Terry Martorano
2017-12-26 14:01:34.000000

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.

Jon Sears
2018-03-13 19:16:52.757465

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

Jon Sears
2018-03-13 20:17:01.251323

My contractor has covered an asphalt shingle roof with 5/8” plywood over which he is installing 26ga standing seam. Looks great! I’m located in ‘rainland’ and the contractor was only able to complete maybe 1/5 of the metal installation. I insisted he cover the exposed plywood with waterproofing which he did but used a cheap product which did little good. The plywood is now wet and will get wetter. He said he will pull the protective material off (when back from vaca) and let the roof dry out and then put an impervious sheet of black plastic on it for the winter. He plans to work on installing the metal during our occasional dry spells. My concern is that the plywood will not really dry in the cold weather and we will have trapped moisture if he ends up installing metal over semi-wet ply.

I have read some of the others similar concerns above but would appreciate your response in any case. This is such an expensive endeavor for me and I am alone and slightly concerned I’m being taken advantage of.

Thank you very much for your reply!

Melissa Reglin
2018-11-25 03:01:33.335451