GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

I recently had a metal roof installed on my house

Linda DuBois | Posted in General Questions on

I recently had a metal roof installed on my house and am wondering if it was installed properly. The roof was installed over two layers of shingles. The roof is over 20 years old with damaged and raised shingles. The contractor applied the metal directly [to the shingles].

I am also concerned about the exposed metal fasteners. There is about a quarter in. gap between the metal panels and the metal fasteners.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Malcolm Taylor | | #1

    The first place to check is the metal roofing manufacturer's website where you will find their installation guide. Most manufacturers specify that new roofing can go over existing shingles if you apply strapping, but some do allow a direct application as long as the old shingles are flat and a slip sheet of underlayment is placed between the two materials to stop abrasion.

    In your case it doesn't seem like either condition was met, so yes it sounds like it was installed improperly. The gaps at the fasteners is particularly worrying. Hope you are able to get it sorted out. Good luck!

  2. Linda DuBois | | #2

    Thank you for your opinion. I did check with the manufacturer over the phone and they recommended using 30 # felt paper and/or ice and water shield as an underlayment.I am noticing raised horizontal lines in the panels already. The contractor cut corners on the job and now I just have to figure out what to do about it.

  3. John Clark | | #3

    Metal roofs will transmit underlying imperfections. That's a disadvantage of over-roofing with them and that's why tearing off the existing shingles is the best thing to do and then insure that the decking is flat. Shingles to some degree hide imperfections in the underlying roof decking.

  4. Douglas Harrison | | #4

    Regarding your comment on the fastening screws, and the gap viewed...Exposed screws generally have a neoprene "O" ring, or similar, so that when they're screwed down, there will be a "moderately" compressed seal between the lower portion of the screw head, and the top surface of the metal roof. It's important that the screws not be torqued down too far, so as to completely squash that "O" ring. Typically speaking, that neoprene seal should "bulge out" just slightly, when viewed directly from above the attached screw head.

  5. Linda DuBois | | #5

    Thank you for providing this information to me. Besides the gap between the metal panels and the ring, some of the screws were applied at an angle. The contractor came over and appeared to be tightening the screws down, but did nothing about the ones set at an angle. This concerns me.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |