Water Puddling or Standing On Flat Roof

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Published: August 13, 2014 Last Updated: May 2, 2021

Many so-called “flat roofs” have some ponding. Flat roofs really shouldn’t be flat. They normally will have at least a ¼ inch to a foot slope, and many roofers prefer more. The more the roof slopes, the less ponding that will occur.

Overtime and with age, a roof may sag a little or develop some low spots. Sometimes they were even built that way.


On many flat roofs the ponding is very shallow and the water evaporates in a few hours or a few days. Yes, no ponding is desirable, but in real life there is often some ponding.

Maintenance or repair

There are products that help eliminate or reduce ponding. These products help fill in the low spots, but they can be a little messy to use and because of this, it is easier to have a roofer do the work. While doing this, you may also want check to see if any of the roof sheeting needs support or repair.

Is the roof leaking ?

Are there any stains on the underside of the roof? Sometimes you can see the roof sheeting, i.e. in a garage area. If you see stains, then the roof may be leaking, however, don’t jump conclusions. If you’re a buyer and see a stain, you may wish to ask the seller if the roof has a leak or if it did leak, did he have it patched or repaired. If so, when and by whom.

Stains on drywall ceilings or even on a wall may be an indication of possible leaking.

Who to consult? Roofing contractor.

Generally ponding or puddling is a maintenance item for a roof and roofers do the maintenance on these roofs. In some circumstances a home owner may do limited maintenance items.

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The roof of my house has water ponding and I want to fill it with cement. Will the new cement bin with the existing

Hello, one of the main causes for standing rainwater on a flat roof is that the roof drain is sitting higher than the roof. Up until now, the solution was to build a wood box to lower it. This is extremely labor and material intensive process. You can use a prefabricated sump pan to get the job done FAST and EASY by DIYer!!

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