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Ponding in rubber roof

I have a ground floor extension approx 4m x4m flat roof on the back of my property.
The felt roof was at least 25 years old so I requested quotes for a rubber roof. I chose a roofer through reviews and reputation after checking their website too.
Originally the roof sloped to a gutter to the right of the extension.
When the roof was removed they said they didn’t need to re insulate as the insulation was to standards required.
I phoned the surveyor to say and get advice. He said it was to British standard and it would be fine They gave me £100 off. I was out for the rest of the day.
Roofers removed all the substantial plywood boarding (no damage or wear on it) and put required/quoted but thinner 16mm OSB boarding in place. It was covered with a full rubber sheet EDPM and finished with fascias.
I wasn’t happy with the finish of the flashing and asked the manager to come and look. I previously sent photographs and emailed him.
He agreed the flashing was poorly fitted. However there had been a lot of rainfall and there was a lot of ponding on the roof. The water does not drain away. It stated on the roof for three days.
The manager said when he was at my property that there was nothing they could do and it would be okay. The job had been done as it should! He said they could have put firrings in but were willing to offer discount! I asked if they checked the slope but he said no they don’t do that just fit to the joists! He says the joists must be bowed!
We agreed that I would think about it and I would get back to him.
However, the roofers came back two days later and fitted an alternative flashing when I wasn’t at home. I had no idea they were on my property whilst I was at work!
When I arrived home and saw they had completed the flashing I phoned and spoke to the surveyor. He was extremely rude and stated there was nothing wrong with the roof and they were doing me a favour? I said it didn’t slope and that it wasn’t draining He said it didn’t before!
I then phoned the manager and complained about the surveyors attitude. He apologised for the roofers being at my property and said he thought I was in, I had told them I work full time!
He offered a few hundred pounds discount ‘as a gesture of good will’ and said the ponding wasn’t a problem! I have been sweeping the rain water off the roof!
I have not signed or paid anything as yet! I expected the job do be excellent from the feedback I read. I have a quote and I have requested the photos of my roof and the stages as the work was carried out. The surveyor told me I would receive these.
I need to be sure that the roof is as it should be.
Update: I have added the board size 16mm OSB. . Also I obviously. had to remove my light as it’s a chandelier, when the roof was initially fitted. As I wasn’t aware they were coming back (re flashing) I didn’t remove it so pieces dropped and broke , due to the roofers being on the roof!
Please advise.

5 Answers from MyBuilder Roofers

Best Answer

It’s really depends how much water the roof is holding. Some flat roofs can hold a small puddle of water here and there,especially big roofs but if done to a good standard and the EPDM up to scratch small puddles won’t cause a problem. If it’s holding a lot of water this is not good amd firings should have been installed. You want a flat roof,not a fish pond!


Answered 1st Sep 2019

A small bit of ponding is expected with no furrings been installed.
However, the volume of water you are describing is quite concerning, especially with you stating thinner boards were installed. I hope they didn’t use 11mm boards because this is not adequate, 18mm boards are the very least in thickness terms you are able to use.
If you can apply pressure to your flat roof safely and it feels soft and has movement in the boards they are inadequate and need changing.


Answered 1st Sep 2019

There seems to have been a few issues with your EDPM flat roof installation, and not being able to see the roof first hand I feel I cannot answer all of the issues you have raised but, alarm bells ring on 2 points you mentioned.
Firstly they shouldn’t have used a thinner ply to board your roof but, should be boarding with an 18mm OSB board with a 2mm gaffer taped expansion gap.
Also the roof should be a warm lay insulation, insulated with celotex or similar product to joist depth. This should also be gaffer taped at the seams to give a near as possible air tight seal to ensure the best insulation properties.


Answered 1st Sep 2019

These problems sound like lack of cumunication lots of flat roofs bow over time and we cover plenty bowed roofs always ask if they want it sorting or not, this is asked before work starts to avoid these situations, if it bowed before and held water then the question really should have been asked. Some people don't mind others do.


Answered 3rd Sep 2019

Hi there when quoting for work in this case a flat roof. All checks should be made before quoting so a client and tradesmen are on the same page. I would measure ,check falls ,discuss all materials that would be used , give a time scale, then if all is excepted we should have a happy customer. I have not had a in happy one so far.
Regards swift home improvements


Answered 3rd Sep 2019

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