help, can anyone advise me on a flat felt roof as we just had extention built 22ft by 13 ft the builders put on flat felt roof but it is holding puddles of rain ! these puddles do not dry up the builder says it will do no damage but i think he is talking builders b....... sureley after a while the rain will get moss, any advice please this is so frustrating please help
flat roof puddles
- Thread starter pamela
- Start date
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2scoops0406
Even flat roofs (rooves?) should have a slight fall to them, no they should not get puddles on them.
did not think my flat roof was suppose to form puddles but my builder seems to think its ok and will be no problem i think he is talking builders b.......... well i will get the local council buider inspector in to take a look as i have not paid for this extention as yet and at 36,grand i want it right, thanks for all advice given oh by the way the roof has only been on a week , oh and the guttering is holding water also . oh and another thing the down pipe from my house runs onto new roof so any water from back of house runs down drain pipe onto new roof i did ask if he could put bend on it and fix it to down pipe on new building but he said no need to it will be ok !!!!!! 
In my experience, this can happen if chipboard has been used under the felt. In the summer the sun heats the roof, the chipboard is softened, as it contains lots of resins/glues and gravity will do its bit and pull the chipboard downwards. After a few years it will puddle. Not a problem with ply or other modern materials.
I wouldn't expect it on a new roof.
I wouldn't expect it on a new roof.
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on the roof when it was built on top of wooden joist the angeled wood tappered from 3inches to nothing some peices were not quiet long enough i noticed ,but when i said to builder this he told me not to say anything as i did not know what i was talking about! well he was right there i dont know anything about building work but i do know my roof shoild not have puddles on it
no no chippings , i spoke to builder and he said it will not be a problem but i am not satisfied so i have the councils building inspector comming out on thursday the council are giving us a small grant towards this as the extention is for disabled use , the cost of extention is 36 thousand this includs bedroom 13x9 and bathroom oh and that leaks but thats another story and that will be fixed but its not the point i believe poor workman ship is to blame , we are paying 29 thousand towards this job and i want it right , thanks for all your help i will let you know how i get on thursday xx
Is the 13ft dimension the fall of the roof ? If so then a 3" fall is somwhere in the right area I am surprised this is puddling i would guess that one of three things is happening
1) where your firrings are not long enough the water is running to the ends of them, (and as the rafters are either at best flat or, judging from your description of your builder, quite possibly running slightly back) and then pooling on the last part of your roof.
2) the roof decking has got wet during the build and is now warped creating puddles
3) The layers of roofing felt have not adhered to the roof properly and have lifted in areas creating a pool.
It is not best practice, but most modern felts can now stand frost action from standing water and are able to stand direct sunlight without the need for reflective chippings.
1) where your firrings are not long enough the water is running to the ends of them, (and as the rafters are either at best flat or, judging from your description of your builder, quite possibly running slightly back) and then pooling on the last part of your roof.
2) the roof decking has got wet during the build and is now warped creating puddles
3) The layers of roofing felt have not adhered to the roof properly and have lifted in areas creating a pool.
It is not best practice, but most modern felts can now stand frost action from standing water and are able to stand direct sunlight without the need for reflective chippings.
Just to add on to chappers post, I've bought 24 3.9m firrings last year and sent them all back because they were all badly cut thus this will give you a flat roof bow which could be another reason for the puddle. I now make my own firring knowing it's dead straight, make a difference for a flat roof.
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2scoops0406
Great stuff I'm sure guys, however I think for a layman (assumption here) is that you shouldn't have puddles forming on a flat roof.
2
2scoops0406
looks like you've definitely got a lip at the front of the roof.
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