I have installed b-vent flashing on my roof which is at at 9/12 slope. I sank nails along the left, right, and top edges that are under the shingles. However, I'm debating if I want to attach the bottom edge. Whether I use gasket screws or nails, I feel it's just making a few additional holes that could potentially leak and that aren't very necessary. The flashing seems sturdily affixed without them and I don't really think water is going to back upwards. I've seen both attached and unattached b-vent flashing. Could I have suggestions as to which is better and why?

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1 Answer 1


I am a firm believer of not nailing the exposed parts of flashing.

I do add roofing tar or other sealant under the flashing.

Normally if the roof slope is 3/12 or greater there is little chance of rain getting under the flashing. Wind driven rain could be an issue, but if sealed properly it is normally minimal or nil.

  • If I seal the exposed edge, do you think it's possible errant water and moisture could build up behind it because there would be no place for it to drain out? Aug 30, 2023 at 14:22
  • if everything is done properly, ( the flashing the shingles) there will be no water behind or under the flashing.
    – RMDman
    Aug 30, 2023 at 14:56

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