How to deal with ponding water on the roof?

The roof protects your home from the elements. It keeps out rain, snow, and sunlight. Although it is intended for this job certain factors can compromise its integrity and cause the roof to leak.

One of the most common causes that may lead to roof leaking is ponding water. It doesn’t only cause leaks but also all kinds of other problems like rot and mold.

The ponding water happens usually when the roof has a low-pitched slope and is unable to efficiently drain off rainwater.

However, every roof may have certain problems that may cause ponding water. Shingles can be curling making the “bowl effect” for water storage.

The roof pitch may be inadequate or deteriorated to let water drain away. These are some of the reasons that may cause ponding water on your roof.

water ponding on roof

Now let’s take a closer look at the problem of ponding water on your roof.

What are the factors that cause it?

What are the methods of removing ponding water? And how to repair or prevent it?

Why does the water pond on the roof?

Ponding water can happen on any type of roof, although it is most common on low-slope commercial roofs. This is usually caused by one of two things: poor drainage or pockets that form as the substrate settles over time.

But the question comes to mind of how long should water remain on the roof in order to call it ponding water.

It’s usual to have standing water on a flat roof for 12 to 36 hours following a rainstorm.

However, according to the National Roofing Contractors Association, any standing water found ponded on a flat roof for more than 2 days needs examination by one of their professional commercial contractors.

Because any water left on the roof after this period of time is considered as ponding water. Here are the most common reasons why ponding water can happen.

Inadequate roof drainage system

The main factor that causes ponding water on the roof is the poor drainage system.

If you’re dealing with a flat roof then the drainage system is usually made of a series of drains that are angled to lead the water away from the roof.

If they’re obstructed or poorly sloped then water can accumulate and cause ponding. Even small obstructions like debris, vegetation, pebbles, etc. can interrupt the flow of drained water on your roof.

Gutters and downspouts that are blocked with debris or leaves can cause ponding water on your roof.

Insufficient roof pitch

The slope is the factor that is most important for a roof to achieve proper drainage. Although there are many flat roofs without any water ponding problems, low-slope roofs are more susceptible to this kind of problem.

The proper pitch is essential for the drainage of rainwater. A roof with a pitch of more than 3 inches for every 12 inches is usually considered to have an adequate slope.

However, if it’s pitched less, then it may require additional design considerations to avoid ponding water.

Roof substrate settling

Another reason that may cause ponding water on the roof is the improper installation or settling of the roof substrate.

The installation of a low-pitch roof usually requires a thicker layer of lightweight tar and gravel substrate to move water away from the roof.

However, if the substrate were improperly laid or settled over time it may create a depression which is also a common cause of ponding water on the roof.

Break down of the roof membrane

The majority of roofing systems are polymer-based, with TPO, EPDM, modified bitumen, and PVC being common examples.

They all have various performance profiles, and they’re all susceptible to breaking down over time owing to the nature of what they face on a daily basis.

In normal conditions, most roof membranes degrade at a rate of 1 to 1.5 miles per year; however, ponding water conditions will damage the membranes significantly quicker.

That’s why it is essential that any ponding water on the roof be dealt with in a timely and proper manner.

Poor roof design

The design of a roof is another key consideration that can contribute to water ponding on the roof.

The main factor here is the edge condition. Roofs with parapets, scuppers, and raised curbs will usually drain properly.

However, if your roof doesn’t have any of these features then it may be susceptible to ponding water.

It’s vital for the best performance that all surfaces have the right pitch and be sloped away from your structure.

In some cases, you might need to cut a notch into a parapet wall or build an extension on top of an edge condition to accommodate drainage.

In fact, most commercial roofing companies usually consider proper design as a critical component of a roofing system.

Inadequate installation workmanship

Lack of proper installation workmanship can be a major factor in ponding water problems. Usually, these kinds of issues are related to the waterproof membrane itself or the gutters and downspouts installation.

These problems might lead to ponding water on the roof if your system wasn’t installed properly.

For instance, inadequate gutter protection will not prevent debris from entering them and eventually clogging up your gutters.

As a result, the gutters will be unable to drain properly and water may accumulate around them.

The age of the roof

As time passes, your roof will show signs of aging. As it matures over the years, minor cracks and openings might develop on the surface of your membrane.

Moreover, building settling or landscaping can cause problems as well.

All these factors may lead to ponding water issues if you don’t monitor their development closely.

If your roof is showing signs of aging or if there has been a significant change in the surrounding environment, then it’s essential to inspect the roof and do proper maintenance work.

Roof drains

All roofs need appropriate drains to control the rate of water flow. They work hand in hand with gutters, downspouts, and splash blocks to channel rainwater away from your structure.

The majority of roofing systems are designed to direct excess rainwater into the drains. However, if they’re clogged or improperly installed then ponding water problems may arise.

For the best performance, it’s vital to inspect your roof regularly and clear out any blockage you can find in your drains.

Moreover, make sure that every drain is properly connected to a downspout or other drainage system. If you see ponding water nearby them then it means something is wrong with the drainage system.

A properly installed and maintained roof will ensure that water drains away from your structure. In the majority of cases, it should never be a problem to control roof ponding.

However, you must do something if you discover a small amount of accumulated water.

If there’s no significant ponding water on your roof then you can monitor the situation and wait.

It is critical to adhere to building codes to prevent water from ponding on the property and generating a slew of issues.

There are a few elements that should be addressed for proper drainage, according to Martin J. Fradua of the University of Massachusetts:

  • Install at least one drain per 10,000 square feet area
  • Keep the max distance between drains 80 feet
  • Use parapet wall scuppers instead of an inboard drainage system. However, size them properly to make sure the flow is not blocked.

What are the potential problems caused by water ponding on the roof?

The main problem caused by water ponding on the roof is leaks. If your roof accumulates even a small amount of water then it’s likely that it will eventually leak into parts of your structure.


Leaks may damage your rooftop, insulation, and other components inside your building.

Furthermore, they can cause mold growth if you’re dealing with severe moisture issues.

Mold Growth

You should avoid delay and get your roof inspected if you notice the first signs of water pondering.

Also, take prompt actions to stop them from getting worse and provide a breeding ground for mold growth.

Ceiling Collapse

Ceiling collapse may also be a significant issue if your roof is not properly installed.

Water ponding can create significant pressure on your ceiling, which might force it to collapse.

Termite & carpenter ants infestation

Termite infestation or carpenter ant invasion may also be a result of water pondering.

If your roof is not properly taken care of then it can become a perfect place for these pests to thrive.

If you discover any sign of infestation, then you will need to take immediate measures to control them. It’s essential to get rid of all termites or carpenter ants before they do significant damage to your property.

Ice formations & membrane damage

Water ponding on the roof may lead to the formation of ice. When water freezes and thaws, it can tear apart the membrane and damage other rooftop components.

Icing formations may also cause slip hazards that may be dangerous for your property or others around you.

How to prevent & fix the water ponding on a roof?

Although roof ponding problems may happen, you can still prevent them before they occur. You can also take prompt actions to fix the problem if you discover any signs of water pondering.

Here are some ways to prevent and fix roof pondering:

Keep your drainage system in proper condition

Your roof drains are vital for taking care of excess water. If they’re clogged or improperly installed then it can cause ponding problems.

Regularly clean your roof drains and get rid of any blockage you can find. You should also check if they’re connected to a proper drainage system, such as the downspout.

If you notice pooling water nearby, then it means there is a problem with your drainage system. Therefore, hire a contractor and get them inspected to ensure that there are no issues.

There are two methods for cleaning gutters: the first one is quick and simple while the second is a little more time-consuming. If you want the quickest results, try this:

Use a garden hose with a pressure nozzle

Use any type of nozzle, such as one used for garden hoses that can shoot straight upwards into your gutter.

This will dislodge any blockage because the pressurized water can push it up and out of the gutter.

Use a gutter vacuum

You may also utilize gutter vacuums to easily clear leaves from the gutter by sucking them up via an entrance at the top of your house, eliminating the need to climb ladders or step out onto any rooftops.

Keep drains debris free

Keeping drains free has been shown to be an excellent technique for reducing severe problems with ponding water on roofs, as well as lesser issues like algae growth or other blockages that could obstruct drainage flow.

Check for roof damage

You should also inspect the roof and check if there are any damages or weak points in your structure.

Water ponding can represent an early sign of roof damage, so it’s necessary to have them inspected.

Sagging or uneven sections on your roof may be a sign of damage, as well as low spots that retain water. In this case, you should repair or replace the weakened parts.

Regular roof maintenance

Periodic inspections and routine maintenance will help you be prepared for potential ponding problems. It can also keep your home protected from other kinds of damage that may be caused by water leaks.

When your roof’s shingles wear out, it’s critical to replace them as soon as possible.

Water leaks inside your home can be costly and dangerous if your tiles are damaged or misplaced.

Install tar paper on your roof

Installing a layer of tar paper material on top of your roof’s waterproofing is one approach to extending its life.

This will help prevent water from seeping into seams and generating leaks, which could lead to more serious issues later on, such as mold or structural damage.

Apply an extra protective layer directly to its surface. This helps to defend against things like rainwater getting in via little holes you may not have noticed before.

Seal around vents and chimneys

Every responsible roofer understands the significance of putting sealant around vents and chimneys to prevent water ponding on the roof.

Apply a coat of caulk where two surfaces meet or use tar paper if there are gaps at connections in pipes that run up through your gutter system.

Use tapered insulation

Tapered polyisocyanurate insulation is a great way to shield your home from leaks by using foam insulation at the top corners of your roof.

Its tapered shape enables it to stop ponding water at the point of contact, which can prevent leaks and damage to your home.

The sloping shape prevents stagnant pools from forming and promotes flowing water to go towards drainage outlets for easy disposal, hence preventing ponding water.

GAF’s EnergyGuardTM Tapered Polyiso Foam Roof Insulation is one of the most popular insulation materials on the market.

This product is available in a range of slopes to accommodate practically any desired slope, with two popular options: 1% (18 inches per foot) and 2% (14% inch per foot).

Roofs can be altered to better deflect water away from the house by utilizing this form of insulation. This means fewer leaks and more structural safety for your home.

Use crickets to keep water from pooling

Crickets are raised in places near a roof or other water-diversion protrusion. Chimney crickets, which are utilized on roofing projects where one part of the building’s slope directly leads to the chimney, are certainly familiar to you.

In these circumstances, small wooden structures placed against the backside of your house can help channel rainfall away from the backside of your house and completely off its surface.

Crickets are quite good at keeping water away from chimneys, HVAC systems, and other difficult-to-drain locations on rooftops.

Achieve positive drainage on a flat roof

If a property owner has a roof where water pools for more than 2 days, their warranty may be voided.

As a result, it is always advisable to implement positive drainage to avoid this problem from the start.

Positive drainage entails creating graded regions on the roof that allow water to flow away from low-lying areas.

This can be done by installing a series of downspouts or gutters that direct rainwater into larger drains for easier removal from your land.

Consider a low slope roof to be the ideal drainage method. The region at the top is taller, allowing gravity to force water into rain gutters and prevent ponding in troubled areas.

When utilized on a big rubber roof, these technologies efficiently convert sections of it into sloped areas for drainage reasons while maintaining the integrity and safety standards of the roof.

Replace The Membrane

The roof membrane is a protective covering that keeps moisture out of the structure.

If the membrane becomes broken, it may be worth replacing the entire device rather than risking structural damage that will cost you considerably more in repairs in the future.

Modern roofing membranes are built to tolerate ponding water, so if you have a flat or low-slope roof, it may be worthwhile to replace the membrane to safeguard your home.

You should also watch the video below because it is a great example of what you could do.


The roof should be designed in such a way that the water flows away from it without much resting on it. This will ensure that the roof lasts longer and is not damaged from water ponding.

A lot of the damage caused by water building up on roofs is preventable. A good design, proper maintenance, and a few simple modifications can help you avoid the headaches and costs associated with ponding water.

Even if you may need to spend a bit more on materials and labor at the outset, it is well worth the cost to prevent many problems down the road.