# New low-slope roof has water-ponding problem



## sf4roof (Jun 4, 2009)

Dear all, we just installed a new roof (modified bitumen with Dibiten Poly/4 APP, one ply with aluminum coating). We are located in San Francisco. 

San Francisco recently start to rain and had a lot of fog (fog season now), and we noticed that the new roof has a water ponding area. See photo here: 

http://img32.yfrog.com/i/dsc0803i.jpg/ 
or 
http://yfrog.com/0odsc08081280x768j 

My questions: 

1. Does this type of water ponding OK? As the water seems to sit there for a while now, and the surface area with water start to turn rusty color (not sure why). If the water continue to sit there for a while, could that potentially create some bigger problem (in SF we have fog all year round, and sometimes sun does not come out very often)? 

2. Usually how would a professional roofer handle/address this type of problem? 

Thanks!


----------



## Ed the Roofer (Sep 15, 2008)

The 2 generally accepted definitions of Ponding Water, are if the puddle remains after either 48 or 72 hours since the last moisture event.

Since you state that you are in fog almost continually, which contains substantial moisture, there is rarely a End Of Moisture point to reflect upon for establishing the issue.

But, with that said, the very large sumped ares that goes across the entire roof does definitely have some issues that would have been better off tended to during the roofing application process.

The orange-ish rusty like color you see may be from the aurface coating deteriorating away or from the petroleums in the modified bitumen roof material starting to leech out from being under water.

Any petroleum based roofing product will lose it's life prematurely if continued under water saturation is left unchecked and not remedied. 

This are needs to be redone otherwise the material will wear out and possibly invade directly through one of the seams or the actual material itself.

Ed 


.http://www.rightwayroofingcompany.com/


----------



## Grumpy (Oct 29, 2008)

In the first phot the triangle you marked out on the upper left is nothing at all to worry about. 

In regards to the sump, that area was designed (for some reason) to be a gutter and is doing it's intended purpose of carrying water. However it does have some standing water, I wonder how deep it is. You may consider a tapered insulation system within the sump to reduce the standing water, but remember that is it's intended purpose to control water flow so you might always have some degree of standing water. 

Ed could be right about the orangish coloring. It could also be rust dripping off the near by mechanicals, or anything that we can't really tell for 100% sure from the photos. 

Something in the first photo that causes me alarm is the fasteners ontop of the coping. Generally I like to see the fasteners placed in the sides of the coping. 


2nd photo does not work for me. 


How would I handle it? Well I do consider myself to be a professional roofer but having said that I've never seen a low slope roof not have some degree of puddling. I have myself created very similiar sumps, once at a home owner's demand and once as a short term fix. 

However I am a roofer and my job is to cover up what is there. Sure if I see something I will bring it to the customer's attention, however not all puddles are visible until after the first rain. This is especially true when tearing off tar and gravel roofs and the old gravel did a good job of hiding the puddle.


----------



## sf4roof (Jun 4, 2009)

Hi Grumpy, thanks for your reply! I really appreciate that!

You mentioned that "Something in the first photo that causes me alarm is the fasteners ontop of the coping. Generally I like to see the fasteners placed in the sides of the coping." Just curious, why would it be better to have the fasteners place in the sides instead of on the top of the coping? Aren't they both exposed to rain and moisture anyway? Thanks!


----------



## c&b roofing (Aug 12, 2009)

You could also could use product called hydro stop barrier guard. You could use the slurry to build it up in those areas. then go over it with the hyro stop elaticmeric and fabric on roof or how every you spell that. that would be the easy fix


----------



## AaronB. (Nov 23, 2008)

I know I would not have placed the filed seam at the transition into the "gutter" like that. Should have been extendeddown to the flast of the "gutter" over a tapered insulation.


----------



## AaronB. (Nov 23, 2008)

c&b roofing said:


> You could also could use product called hydro stop barrier guard. You could use the slurry to build it up in those areas. then go over it with the hyro stop elaticmeric and fabric on roof or how every you spell that. that would be the easy fix


What type of product is the slurry? I only ask because you need complete drainage with elstomerics in order for the acrylic not to absorb water and wask away.


----------



## glasscockroofing (Oct 23, 2009)

i agree with grump and ed the roofer. it sound like they know what there talking about. if there are no drains in that area and the water just sits waiting for the for the sun. in my opinion it would cause problem in the furture. maybe one to two years but i have seen swimming pools on top builds that never leaked. unfortunatly i dont think there is something you can just slap on top to fix it. if there is i hope it is a well gaurded secret or we all will be out of a job.


----------



## AaronB. (Nov 23, 2008)

Well, polyurea would keep the water ou... it can withstand indefinite water soak. I hope to put all you guys out of a job LOL J/k


----------



## Grumpy (Oct 29, 2008)

Aaron, there is a tool for every job and one one size fits all solutions. Don't put all your eggs into one basket. It's great to be a specialist, but it's also good to have more than one bullet in your gun incase the first shot misses.


----------



## Marty1234 (Jan 18, 2012)

Ive used nothing but dibiten since it was introduced about 26 years ago. I do at "least" one per week and have never had problems with Ponding water which most roofs have to some degree..the tech from Italy who taught me mentioned a roof that was being monitored, I believe in canada, that not only had severe Ponding water but would freeze for months at a time. This roof had been on for years with no problem..every so often I'll check on the first dibiten roof I did, back then they were non granulated only and we'd coat them with silver paint. The roof is still fine..On occasion or in blind valleys I'll torch down a smooth layer first..the most critical aspects to torch down is the visable overflow on all seams "especially" the side laps and the sandwiching of all metal..


----------



## D'Angelo&Sons (Aug 21, 2015)

I can't really see your photos but from what you describe you could have a bigger problem on your hands if you don't address it quickly. If the pooling water remains longer than 72 hours, and since you've mentioned that SF gets fogy quite often this pooling can persist even beyond the 72 hour period, you might want to have a professional have a look at it.

Sorry I can't be more helpful without seeing the images.


----------

