How to Remove Standing Water on Flat Roof

Standing water on a flat roof is one of the most severe problems you can have. It will cause rot, mold, and mildew growth to occur under the shingle membrane. This type of moisture intrusion can lead to premature failure of your entire roof system.

How to Remove Standing Water on Flat Roof

When it rains or snows too much, and there is standing water on your flat roof, you need to take action immediately! There are several ways you can remove standing water from a flat roof, including using a squeegee, using an air compressor with a pressure washer nozzle attachment, or simply waiting for it to dry up by itself.

You should never use any chemical product such as bleach to try and get rid of this problem because that could do more damage than good. Instead, this article will teach you how to remove standing water on flat roof with a few simple steps. 

Steps to Follow on How to Remove Standing Water on Flat Roof

Step One: Stop Water from Entering the Roof

Turn off any nearby running water to avoid making the situation worse. If you didn’t find standing water on your roof before, don’t assume it’s okay to leave all of your fixtures running as usual – turn them off so that no new rain will come in. Likewise, if a sump pump is currently draining your roof, make sure that it is turned off.

If the water is from a leak in your home, find and fix it as soon as possible to avoid further leaks. If the water is from rainfall, you can leave it to dry on its own – be sure to fix the source of the leak so that you don’t have a repeat problem.

Stop Water Leakage From Concrete Roof From Home

Step Two: Use a Sponge or Rag to Suck up Water

Cover your sponge or rag with clean water and place it into an airtight container. Then, slowly bring the water-bearing sponge or rag to your roof. Do this methodically and systematically, as a leak that you don’t see could be causing a drip right over where you’re standing.

Use a bucket underneath where you’ll stand so that any drips will land in the container instead of on your body. Take care not to slip off or harm your roof with the sponge or rag. If you’re working on a pitched roof, do not bring the water-bearing sponge or rag to your roof at all. Doing so could cause you to slip and fall or harm your roof with dripping water.

Step Three: Let the Water Settle and Drain

Let your bucket sit for several minutes, keeping an eye on it to ensure that water droplets aren’t forming. If they do appear, further steps will be necessary to remove them (see below). With some luck or good timing, the collected water will no longer be in a liquid state and will be able to drip off the side of your roof slowly. 

Keep an eye on the water level in your bucket and check it every few minutes. When you see that the water is no longer collecting in your bucket, take the hose off of the side of the roof to stop drawing water up from underneath your shingles. If your bucket could not catch all of the standing water on your roof, you can lay a tarp or some plastic sheet over the top of your flat roof.

Step Four: Drain Standing Water Puddles

If you do not drain the standing water puddles, they will freeze in cold weather. This could cause damage to your roof when it thaws out come springtime. Excess water on a flat roof can be dangerous, so it needs to be removed as soon as possible. If the standing water is from ice dams or snow, use a metal scraper to remove what you can and top up with hot water if necessary.

If the puddles are from rain or melted snow, the best way to remove the standing water is to place a submersible pump into the puddle and allow it to pump out. You can find these pumps at any hardware store or home improvement warehouse. Keep in mind that if you have a serious drainage issue, this procedure will likely take several hours, so it’s best to tackle this job on a sunny day when you have the time to let it run.

Is It Ok to Have Standing Water on a Flat Roof?

Although a flat roof is typically designed to provide waterproof protection, a certain amount of moisture can accumulate beneath the surface. This is referred to as “perched water” or “intermittent water,” and it can be the result of poor drainage conditions around the perimeter of your home.

When perched water occurs on a flat roof, it is best to get rid of it. It may also be beneficial to investigate why it is occurring to prevent future problems. In order to remove the standing water from your flat roof, you will need a garden hose or firehose with a spray nozzle that is capable of producing a strong jet of water.

How Long Can Water Sit on a Flat Roof?

Once the water has been allowed to stand on a flat roof, the longer it remains there, the more significant opportunity for damage to occur. Whenever water stands on a roof – even if no damage occurs – temperatures can fluctuate and lead to condensation.

This will then cause rusting of any metal components present and can even encourage the growth of mold. The result is that any damage will be worsened because it was compounded by allowing water to remain on a flat roof for an extended time.

A Leak Causes Internal Damage

Frequently Asked Question

Is It Ok to Have Standing Water on a Flat Roof?

In general, it is not recommended to have standing water on a flat roof. It can cause damage to the roofing materials and lead to leaks which will require costly repairs or replacement of the entire roof.

In addition, standing water may also encourage the growth of mold and mildew, which are harmful to your health as well as your home’s indoor air quality.

How Long Can Water Stay on Flat Roof?

“Not very long.” The water will start evaporating and losing moisture in the air quickly.

An example of this would be a flat roof that has been flooded with rainwater. After the storm, the water will start evaporating because it is not supported by any structure on the roof. This process may take a few hours or days, depending on how much rain falls from the sky.

How Much Ponding Is Acceptable on a Flat Roof?

It is important to know the limits of ponding on a flat roof before deciding how much water you can have on your property.

A standard rule of thumb for ponding is that there should be no more than 3 inches of water on the surface of the roof at any given time.

However, if you have a flat roof and it has been raining heavily, then this number may need to be increased up to 4 inches or even 5 inches, depending on how high your ponding height is.


The problem of standing water on a flat roof is prevalent. If left untreated, the moisture can lead to mold and mildew growth which may cause health problems for those living in the home or business. In addition, standing water causes significant damage over time, so you must take steps now to avoid future consequences.

One way to resolve this issue is by installing an EPDM rubber membrane between your existing shingles. This will prevent any leaking from getting into your house and help keep the ground around your property dry as well! The infomercial style of this article has shared information on how to remove standing water on flat roof.

Check it out also – How to Jack Up a Roof .

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