Door threshold hight on Roof Deck: Is this a code violation?

shw001September 3, 2013

There is a flat roof (about 300 square feet) on a one-story part of my house. There is a door out to it from one of the bedrooms. The door threshold is 3 inches above the roof deck. I am thinking of adding insulation to the roof and a new rubber/plastic roof membrane which would reduce the threshold height to only 1/2 inch above the deck. Does anyone see any practical issues or building code issues with such a small clearance?

We do not use this roof, except for occasional maintenance, like gutter cleaning.

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Water is going to sit and probably leak through a door with a sill of only that height, especially wind driven rain.

    Bookmark   September 3, 2013 at 3:06PM
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Replacing the door with a window would solve all your concerns.

    Bookmark   September 4, 2013 at 12:16AM
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There's a reason not to cross-post.

A door threshold is supposed to slope to the exterior to drain water off. However, in a cold climate you always want a much higher threshold to prevent problems with snow and snow melt on the threshold.

    Bookmark   September 4, 2013 at 7:42AM
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If the insulation is to retain heat, there will probably be snow that will sit against the door. If it is to keep heat out, you need a step to stop wind blown rain.

But 1/2" IMO is so small it will effectively be no step which is a very bad idea.

This post was edited by Renovator8 on Wed, Sep 4, 13 at 18:56

    Bookmark   September 4, 2013 at 6:50PM
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Thanks for all the good comments

IâÂÂve considered replacing the door with a window, but decided the door is a good convenience.

I am not sure how wind-blown rain would be more of a problem than with the 1/2 inch step than with the current 3-inch step? The threshold is concrete and does slope pretty well and extends out about 8 inches from the door. There is also a storm door that the threshold goes under and extends out about 2 inches past the storm door. So direct rain is not likely to be a problem.

Why would wind-driven rain be a problem? There is not likely to be puddling near the door because The slope of the roof is now 1/8 inch per foot, and after the new tapered insulation will be ü inch per foot.

Snow is an important point. We have never had a problem before. I suspect that enough heat is escaping from the building through the brick & block walls and door that it rapidly melts any accumulation within say 2 inches of the wall and door. However, anything can happen with ice and snow. I suppose a 2-3 inch high snow or ice pile can prevent drainage and a puddle can build up behind it. Is this what you meant? If so, any solutions??

Worthy, is there a rule about cross-posting? I just looked and couldnâÂÂt find it. If this is a problem, thanks for the warning. In the past, I have done this, if there was no interest in the post, or I realized it would be a better fit in another forum, but waited a longer time before posting in another forum.

    Bookmark   September 8, 2013 at 10:31PM
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I am not an expert, just an average person...this strikes me as a terrible idea. If we did 1/2" threshold height I would worry greatly about water and snow intrusion.

    Bookmark   September 9, 2013 at 1:59PM
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