Ponding on Firestone EPDM Flat Roof After Replacement
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Ponding on Firestone EPDM Flat Roof After Replacement

Post by OldDIYer » Thu Oct 30, 2014 6:58 pm

Although there were no leaks or ponding on our garage 36 year old felt flat roof my wife and I decided to have it replaced with Firestone EPDM to prepare our home for security and less hassle in old age. Originally I was going to give the job to a recommended roofer who I believed I could trust but friends and family doubted the value of a 20 year guarantee because he was a “One man band”. I therefore decided to pay more and used a big company that is registered with the Confederation of Roofing Contractors, Trustmark, Construction Line and CHAS.

Their website and adverts state:

1. “All our employees are qualified tradesmen, and each pride themselves on quality workmanship. As a company, this only adds to our reputation of being the very best in the area.”

2. “All our fitters are fully trained and firestone registered, we have 15 years’ experience in the installation of this fabulous product making xxxx flat roofing easily the most established EPDM installers in the xxxx area.”

Unfortunately, after many weeks of not stop summer sunshine they came on the first day of rain with very heavy rain being forecast in a couple of hours. I asked if they should delay until a better day but was told that 5 workers would get the OSB boards fixed on fast and as long as they had the EPDM on top it would act as a tarpaulin and there would be no problem. As fully trained qualified tradesmen I had to trust them. They did get the roof covered before the storm came and completed the rest of the work between showers.

I did not realise until a couple of days after I paid the bill in full that there are two areas of bad ponding totalling about 8 square metres and measured 10 mm deep and not completely clearing after a week of continuous hot dry sunny days. This is a lot of standing water waiting to drain through any small hole that may occur in the surface. The last area of OSB boarding, next to the gutter, is only 550 mm wide and the outer edge is over 10mm higher than the middle. I believe that no consideration was given to any fall at the edge next to the gutter because of rushing the job to beat the rain. When it rains the two areas of water combine into one huge pond before eventually moving like a river to tip over into the gutter along its length.

The roof can be seen from the main road and friends are asking “Why have you got a pool on your roof?” My neighbour higher up the street said “Having a river on your roof does not seem right to me”. The roofing manager insists that this is not a problem and because there is a continuous layer of EPDM and no joins it is perfectly acceptable and it will never leak. He further suggests that they could ballast the roof (If I pay for the stones) so that the ponding would not be seen.

Are there any roofers out there that could give their opinions on this job? I think the edge should be redone but this is not going to be cheap and the roofer is obviously rejecting this.

For the sake of clarity I have omitted mentioning other faults which have since been rectified by the roofer.
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Re: Ponding on Firestone EPDM Flat Roof After Replacement

Post by RubberRoofer » Wed Jan 07, 2015 4:26 pm

Difficult one.

When you were quoted / invoiced for the works was their any mention of "Eliminate ponding"?

The guys will have laid OSB3 to the structural joists. Unless there was specific mention of fitting firrings to eliminate ponding then they have only followed the original profile of the roof.

It is very likely that some ponding was pre-existing, and you couldn't see it because of chippings??

I can't really help you in terms of what should have been done or not, if there was little fall (below 1:60) then they should have asked if there was ponding. If there were chippings on top they should have advised you that these would be hiding any ponding, and perhaps measured the fall of the roof.

However, in some ways they are right - EPDM will support standing water perfectly well. So unless it leaks, it shouldn't give any problems at all for you.

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