I have a glass-roofed lean to conservatory with a shallow roof pitch. After heavy rain there is standing water at the lowest part of the roof where it enters the gutter. What would be the least acceptable pitch of the roof be to ensure complete runoff of the water?

  • 2
    If your roof was perfectly flat, then any pitch would cause "complete run off of the water". Your problem is that you have a dip, or low spot. Commented Oct 20, 2017 at 15:00
  • Well, disregarding that pesky surface tension thing, anyway.
    – isherwood
    Commented Oct 20, 2017 at 15:44

1 Answer 1


As Jimmy said, apparently the area in question effectively has no pitch. It's a low spot possibly due to poor workmanship on the drip edge. Some roofers install it incorrectly, creating a "ski jump" at the eave.

As you have a glass roof, I'm really not sure what your situation is. A photo would help us offer more specific advice.

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