Roof of front porch (portico) has horizontal "ridges". Water ponds within the areas defined by these ridges. Should I be concerned?

The roof of our portico (front porch with columns and a roof) seems to have these horizontal “ridges” (not sure if that is the correct term). I’m not sure if these ridges are normal or a deficiency in the roof. Water seems to pond for a few hours within the areas defined by these ridges. The water does drain when there is enough of it but once the water level gets sufficiently low it stops draining and just gets absorbed into the roof material over the course of a few hours.

I took the below photo outside of the window of the adjacent bedroom. Note that the water in the photo is from a test using a bucket.

Typically when it rains the water doesn’t pond this much because the roof of our home blocks most of it from landing on the roof of the portico.


  1. Should I be concerned or is this level of “ponding” normal? Note that after some hours the water seems to absorb into the roof material.

  2. What are these “ridges”? Are they a feature of the roof - meant to channel the water or something? Or is it a deficiency in the roof?

Basically I want to know if this is something that the builder should fix (it’s new construction) or that I should fix if they’re not going to do it.

Thanks in advance.

Here is another photo, closer up:

Thanks for any responses.

If it dries up in a few hours, its great.
Its a flat roof.
I think it even takes a little longer than that.
The sun must have a good path to get to it.

Ponding is bad.
But this doesnt meet the definition of ponding.


I think that the material itself absorbs much of the water.

I’ve since heard that the “ridges” on the top layer are actually the seams of the base layer. Is that right? Are they normal?

Thanks for the response.

They are the overlaps of the mod bit. And no, the material does not absorb water. It is diffused somewhat by the granular surfacing. For warranty purposes, “ponding” is defined as water that remains on a roof 48 hours after a rain. There is nothing wrong with your roof.

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Thanks for the information. I was wondering how the water that’s trapped in the areas defined by the seams / ridges (as per the photos) clears out without evaporating and without draining in the normal way. Absorption was the only thing I could think of. Does the granular surfacing somehow allow the water to (eventually) exit from these areas? How does that work? Shouldn’t gravity just keep the water in place until it evaporates? The water in the aforementioned areas does stop draining once the water level gets sufficiently low (at least it stops draining in the normal way) and just seems to sit there. But then after some hours pass, it’s nearly gone. Even when it’s cold and the sun isn’t out.

From what I see, the roofer did and awesome detail job on your roof. With all the corners and tight quarters to work in, that was not easy. If he put that much effort into the job you can rightly assume the rest of it is to specs or better. I see a lot of crappy and borderline work, this is pretty.