In my attic today I noted that where two different roof lines meet and overlap there is a large visible gap where light was coming in.

It looks like they shingled the lower roof and then built the higher roof above since you can see shingles inside the attic. I am guessing this gap is reducing heating/cooling efficiency, moisture, and could let critters in so I want to fill it properly.

I was thinking some orange canned spray foam, but not sure if I need to do something special here in this case.

photo of gap

  • 3
    It's not doing anything harmful with regard to efficiency. Your attic should be well ventilated. The only concerns are water intrusion and pests. Photos from the outside would be more useful, as that's where this type of thing is normally addressed.
    – isherwood
    Jan 8 '20 at 21:50
  • 2
    I had a cabin in the mountains many years back it had a cedar shake roof and on a sunny day you could see light in hundreds of locations , never a drip even when covered with snow. I would not start throwing $ or spray foam at something , do you realize there are vents on the roof for a reason and vents at soffits, I agree with Isherwood we need to see it from the outside.
    – Ed Beal
    Jan 8 '20 at 22:02
  • i amokay i'll try to get up there and get the angle. I think I am more concerned with pests getting in.
    – HelpEric
    Jan 9 '20 at 1:14
  • The inside corner of a pitched roof; a flashing nightmare, +1
    – Mazura
    Jan 9 '20 at 1:40

If your only concerned about critters, depending on the actual size of the gap (mouse sized to raccoon sized) a "combination of chicken wire-like mesh and rolled fiberglass insulation pressed gently into gap should work. I wouldn't spray foam alone, critters of all kinds could still chew and peck through it.

This is a sure sign that the roof line/rooms are not original to the house and proper integration of it was not incorporated into existing structure properly. I would look closely for other issues. The attic ventilation is important, so the gap is acceptable for that, however there should already be adequate ventilation. The concern remains to be wildlife intrusion, structural integrity and severe weather. Water could be forced up into the gap more readily then soffit ventilation due to the sloping roof line beneath it. And shingles need to rest upon a structural surface underneath them. Here in Florida during hurricane season winds would rip those shingles off and several more with it increasing the amount of rain that could soak the space and anything below.

  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know the details of contributing here. Mar 21 '20 at 21:59

It is not doing any harm as far as heating or cooling your house but to stop possible critters and water damage you will need to block with flashing if it is on the roof side or sofit / fahcia should have gone further. Looks like poor craftman ship.

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