Standing water on a flat roof for 12-36 hours after a rain storm can be normal, but according to the National Roofing Contractors Association, any water found ponding on flat roofs for longer than 2 full days should be examined by a professional commercial roofing contractor.
Should water sit on flat roof?
Roof systems are simply not designed to hold water. Even “flat” roofs contain a slight slope to maintain positive drainage. ... Collect dirt, which may cause the growth of vegetation or telegraph mud cracking to the roof below.Mar 9, 2017
How much ponding is acceptable on a flat roof UK?
According to BS 6229 & BS 8217, flat roofs should be designed with minimum falls of 1:40 to ensure a finished fall of 1:80 can be achieved, allowing for any inaccuracies in the construction. This applies to general roof areas along with any internal gutters.
Is it OK for water to sit on flat roof?
Roof systems are simply not designed to hold water. Even “flat” roofs contain a slight slope to maintain positive drainage. ... Collect dirt, which may cause the growth of vegetation or telegraph mud cracking to the roof below.Mar 9, 2017
Should there be ponding on a flat roof?
Although immediate leakage is not likely to occur, recurring ponding can cause damage to the roof. But the best thing to do is to keep your roof in tip-top shape to avoid major damages and to also keep it at optimum performance levels. That is also the best way to get the most out of your roof over the years.Aug 4, 2020
What is the minimum slope per foot on a flat roof?
1/4 inch per foot
How much pooling on flat roof is acceptable?
The acceptable amount is the amount that will drain off or dry within those 48 hours of conditions conducive to drying. There is no set amount as it will vary depending on how well the roof was designed and installed.Jun 4, 2018
Is ponding water acceptable on a flat roof?
So how much ponding is acceptable on a flat roof? Specifically, water must remain on the roof for 24-48 hours for the National Roofing Contractor's Association (NRCA) to consider it ponding. If you have this leftover water, you may notice it collects in dips in the roof or around drains.Mar 10, 2021