Exposed Fasteners: Leaking or Condensation?
I am not a huge fan of exposed fasteners for roofs on residential applications. Probably 80% of the questions I receive about problems with metal roofs pertain to these types of panels. That said, I am happy to help when I can.
I recently received the following question from Jane:
Q. I noticed my inside ceiling insulation was wet in a strip on both sides of the ceiling where it appears that the screws were put in in the metal roofing. Though I am 80, I still know nothing about roofing. I started to put silver tar on the roof, but only put it on half of the roof because someone told me that I needed to calk around each screw because you could see where some of the screws were crooked. What kind of calk is the best to use? Have I ruined the metal roof with the tar I put on? Thank you for your help.
Here is my response:
A. Thanks. There is a chance what you see in the attic is due to condensation forming on the screws. The condensation would be the result of moisture inside the home reaching the attic and not being properly vented out. The condensation forms on the screw tips because they are transmitting cold from the outside. One thing you might do is wait for rain on a warmer day and, while it’s still warm outside, check and see if the screws seem to be leaking. If not, then I am guessing this is actually condensation. If it is condensation, try to increase the attic ventilation.
If you decide to seal the screws (keeping in mind that one option is to replace the exposed fasteners with new, larger diameter screws), I would suggest some quality butyl or co-ether sealant. You should still be able to seal over the screws you have coated.
Good luck, and be careful!
Todd Miller has spent his entire career in the metal building products manufacturing industry. He is president of Isaiah Industries, an organization recognized as one of the world’s leading metal roofing manufacturers. Todd is currently Vice President of the MRA (Metal Roofing Association) and a Past Chair of MCA (Metal Construction Association). Through his website, he strives to raise the bar on standards and practices to provide property owners with the best possible products for successful roofing projects.
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