# Pooling on PVC Roof



## techweb (Nov 6, 2020)

Hi,

Having recently had a defective flat roof replaced, I've noticed an issue with pooling water. In fairness the old roof suffered with it to some extent but less so as the outlet was made up of the membrane material. The new outlet is a single piece welded to the PVC and sits ever so slightly higher. Effectively there is a small step up to the outlet which is far from ideal. I mentioned it to the roofer and he explained that the membrane would be unaffected by this and in fact could take being soaked throughout it's life and not effect the guarantee. The details on IKO Polymeric's own site second the fact the membrane can withstand pooling. It was my understanding however that as a rule standing water should be gone within 48 hours of the last rain event...

We had some heavy rain overnight Tuesday and early into Wednesday. I've attached some pictures below with a timeline of the pooling.

This was the roof 5 hours after rain:









13 hours after rain: 










50 hours after rain: 










83 hours after rain:










I am ultimately sticking down a protective fleece, paving support pads and then promenade slabs on this deck so that may or may not help to a certain extent. Should I be concerned at this pooling? What I have researched suggests not, although ideally the water should run off freely.

I'm not really minded to ask folks to start pulling this apart now etc as that would mean disturbing the lead flashing and lowering the outlet in the wall.

Please let me know your thoughts...


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## techweb (Nov 6, 2020)

So... with all the recent rain, the roof hasn't dried out since I started this topic. With the downpours overnight, it's back to where it was. I'd estimate ~30 liters just standing.

Most people I speak to say they wouldn't worry about it... I think I'll have to accept and live with it. I just like things to be right.

Hopefully the protective fleece, support pads and slabs will help raise the level and shift this. 










I reached out directly to IKO Polymeric and they stated that their membrane can withstand even severe ponding without affecting it or the guarantee. However, they did state (as I knew) it is good practice and part of the BS standards to ensure water drains off as quickly as possible.

I think this will be yet another lesson for me in hindsight... I wish I had made a point about wanting to ensure water drains off the roof quickly and not stand.

Whilst the roofer recognizes the water remaining on the roof is not ideal, trying to resolve it now would involve extensive work that he believes in unnecessary.


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## Deerfly (Mar 14, 2021)

Did the completed roof come with a warranty? I would believe the TPO manufacturer would have a warranty with their roof system if it was paid for as part of the complete installation. As you stated ponding with most low sloped roof systems have a set amount of hours in which ponding needs to evaporate in. If a warranty was issued with the roof system, typically an inspector from the manufacturer comes out after completion and inspects to make sure the work and details meet the specs set by the manufacturer. This ponding would not pass.

Was insulation added when the roof was re- done? This issue would have been recognized right away before the membrane was adhered down. Looks as though a 1/2" cover board over the existing level of insulation would have taken care of the problem.


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## techweb (Nov 6, 2020)

Thanks for responding...

Yes it does, although I am yet to receive it. The guy that completed the works has a good name locally and does lots of work for builders etc.

IKO Polymeric make the membrane and they advised me that whilst the roof should have a fall and that water should not pond; the ponding will not affect the life or guarantee of the membrane.

The roof is built up of a vapour barrier, insulation and then ply on top. This roofer didn't touch the deck though, just replaced the membrane. I wish I'd made a point of asking for falls to be checked and to ensure ponding wasn't going to be an issue but a layman like me doesn't think like that until they learn 

There is a fall to the roof, the problem is the outlet. There is effectively a step up and that means that water ponds up to a certain level and then remains until it dries. I hope that once I get the protective fleece, pads and slabs down on it again, this will raise the water level and get the majority of it off the roof; perhaps that's wishing thinking.

I agree overlaying a piece of ply to raise the level and prevent the step up to the outlet would have worked or indeed cutting the outlet a little lower in the wall.


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## photoshop (Feb 20, 2014)

If this was an asphaltic roof system, the warranty will typically exclude coverage at areas that pond water. Ponding is defined as water that sits for more than 48 hours. This is obviously not an asphaltic roof system so the ponding issue as it relates to the warranty is a non issue. Having said this, you mentioned that you would be putting overburden in place. I would recommend having the installing contractor lower the scupper and reflash as required. If this is all it would take to remedy this problem you should do it before installing the overburden. Really though, the roofer should have either provided the correct thickness of insulation or lowered the scupper a bit to accommodate proper drainage. One other thing.... If you're going to cover the roof and scupper with overburden, it may make sense to install an overflow/emergency scupper about 2-4" off the roof surface and relatively close to the primary. not that the primary would ever become clogged but for piece of mind that if it ever did, your roof wouldn't cave in because of the weight of the water combined with the weight of the paver.


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