Phoenix Commercial Flat Roof Ponding

I have been reading this forum on and off over the last several months; I searched “ponding” and made my way through 85 pages of posts before I ran out of gas and ended up in posts completed in 2007. All that being said, I believe that I am ready to tap into the collective knowledge base. I have a commercial building in Phoenix, re-roofed in 2006 with what is described as a fiberglass base sheet and two layers of fiberglass felt hot moped with a mineral cap sheet, seams sealed by three coursing. Bottom line, 3-year old roof failed (leaked) repetitively in subsequent years :frowning: (see Pictures to follow). One Pick is the ponding pre-total failure, another is clearly the failure, and the others are current ponding and leakage post-reconstruction. The original roofer had disappeared somewhere in the first two years never addressing the repetitive ponding/leaking. The new roofer during the reconstruction did build-up new crickets in the corner in an attempt to direct water to the scupper better. The reconstruction roofer wants to do SPF to address the slope/drainage issues for another 50 G’s!!!I beleive that the scuppers are the root problem, as I had stated during the reconstruction, they are inches ABOVE where the roof edge meets the external walls. I have not read any threads that addressed structural changes to scuppers; this is a poured in place concrete wall structure. I have read plenty of posts where total tear-off and tapered insulation is the preferred plan to address slope and drainage. It’s the desert and the irony is I have a water leak issue. It’s hot as hell, I have HVAC guys up there all the time, there are no tree issues, but I do have a pigeon problem, I need some viable solutions keeping this in mind. Any ideas would be greatly appreciated, thanks in advance.

Expensive yes, but I think your best option is to tear it all up, put down 1/4 taper iso, and 1/2 taper iso in your areas where you need crickets. I hate any roof with ponding water. Its no good.
You might consider adding drains too.

I’m sure that Cerb will respond, he will have good advice.

So basically you are asking if you can lower the scuppers in tilt-wall panels? Yes, you can saw cut the hole lower in the wall if needed. Of course, you could also add drains if required, or add tapered insulation.

( IMO )I would first look into strategically installing roof drains. I have seen tapered systems installed where the water still ponds because the plane of the original surface was not leveled out before the tapered was installed. So what you have is a resulting tapered system with a “belly” in it that still holds water. This is especially true if you only use a 1/4" or 1/2" slope.

Other wise if roof drains cannot be installed and you do install crickets to solve the problem make sure you create enough slope to indeed drain the water to the scuppers. And if the scuppers need lowered to make them function properly then definitely lower them. It’s not an easy task to cut through solid concrete tilt up walls but it can be done.

This is one of those projects where you will be best served to have this work done by a contractor who is willing to do what it takes to truly correct the problem. The guy who is willing to do what it takes to “solve” the problem is going to cost more than the guy who says “will lets try this” or " I think this will work"

I have bid on several projects similar to this over the years. Some I got some I did not get. The reason I did not get the jobs was because my bid was several thousand dollars above those I was bidding against because I was not going to bid on what “might “work to solve the problem.

Thus I have seen these kind of projects get “re-workedâ€Â


Although I love the foam idea (since I do foam), lowering the scuppers would prolly be the best bet at this time IF the location of said scuppers is the only issue causing the ponding.

If your roof structure is now bellied at all because of the time spent ponding, then you may have other issues. This can be checked with a line and line level.

Thanks for the response fellas! First of all, based upon what little you can see in the pix, do I have a mod bit roof, apart from a total tear-off, does my existing roof surface limit my options? Options: (1) tear-off and re-roof with iso, as mentioned by AaronB and roofrite there may be structural slope issue and it may not solve the ponding, merely shift it around, especially with my scupper height. (2) Foam, I have read conflicting posts on whether or not you can or “should” foam over existing roof surfaces, or would we be talking about a tear-off as well. Can foam really stand up the HVAC guy? (3) install what I am understanding are internal drains, how exactly does that work, I have a lot of protrusions for HVAC, electrical, water supply, etc., am I not creating yet another potential water entry point. (4) cut in some crickets that run down-slope to direct water into a channel towards the scupper. (5) lower the scuppers, I would assume that not just anyone is qualified to saw-cut in new scuppers, not a normal roofing task.

AaronB, you mentioned a line and line level, is this standard procedure that my original roofer obviously skipped or ignored?

Cerberus, do you have any consultant contacts in Phoenix? I would think that a roof system that holds up in Houston would be overkill in Phoenix, and I don’t mind a little overkill.

roofrite, I couldn’t agree more on the “right” contractor, I can’t afford to make another mistake!

I am not afraid to spend some money, I’m in this property for the long haul and want to make an infromed and correct decisions.

Roof drains are very easy to install and would be your quickest easiest fix,cant believe no ones suggested installing drains.I would assume they are trying to make as much as they can repairing it,as long as you can run pvc pipe below your drain whole its no big deal,cut the drain in flash it to the roof and run the pvc.Normally done in 3 or 4 hrs tops.

We install chopped fiberglass emulsion roof systems which are very common in California and we could install right over that granulated surface and give you a damn good roof,i dont know who installing in your area but im sure theres somebody doing it.The nice thing is the chopped fiberglass makes the roof completly seamless and can be top coated with aluminum emulsion,this is normally a much cheaper alternative to tearing off or foam.Roofs with granulated surfaces are my favorite to chopp as they really make one hell of a roof.Check it out on line,lots of video of it going down.

thanks for the response, chopped FG emulsion, I havn’t heard about that process as of yet, will check it out!


Well, the line and level is used basically to tell where the ponding will be. I don’t know if anyone else uses it, but it works well.

As far as the foam goes, a 3# density foam roof is one of the best you can get. We use this density specifically for roofing because it stands up so well to traffic and abuse.

It can be placed where you need it as you need it. Those that are anti-foam are only anti foam because they fear what they don’t know.

And RObert is correct…

As long as there is proper drainage, then chopped fiberglass and asphalt emulsion is a lot cheaper than foam. He neglects to mention, though, that you will never have to replace a properly installed foam roof, and that the chopped glass and asphalt roofing provides no R value.

I am thinking that a seamless insulating roofing system that never needs replacement in the middle of the desert would be a good thing. The savings on HVAC will pay for the roof in short order.

AaronB, thanks for the response. Can I SPF over existing roof material?

I believe that I have a mod bit roof (please see my pix) and I have to remove some of the existing roof material down to supports to inspect the degree of water damage.

Roofboss, you out there, you are the only AZ contributer out there that I can see.

RobertF, I checked out your chopped FG emulsion link. I am deathly afraid of covering over a ponding issue versus dealing with the underlying problem.

I already had one collapse, I can’t ignore the potential for another, given it’s documented history, I would be on the liability hook.

I suggested installing roof drains first and you do have a granulated modified bitumen in the pics.Is it possible to install drains on this roof?If your worried about the additional wieght of the chopped glass it shoudnt be an issue if you have proper drainage.The spf can be applied to slope,you just need to make sure you get a good spray man.

Actually, he means granule-surfaced modified bitumen, as granulated mod. bit. would look like little gummy, black, granules. For example, sugar is granulated, modified bitumen is not.

And sorry RobertF, this isn’t a knock on you as there are many people who mislabel the product. There are even some that call mod. bit. “rubber”. Anyway, it is just a pet peeve of mine when I hear “rubber” or “granulated mod. bit” as neither is correct.

Per Merriam-Webster:

Main Entry: gran·u·late
Pronunciation: \ˈgran-yÉ™-ËŒlÄÂ