woman holding umbrella in her home on phone with roofing company for leak
June 23, 2021
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Flat Roof Leaks vs Sloped Roof Leaks

The differences between sloped and flat roofs necessitate a different approach to finding leaks because the water flows uniquely with each roof. Sloped roofs have the advantage that the water will run downward, and you can easily follow the water trail back to the source of the roofing leak. With a flat roof, the water will flow less predictably, and it can pool or flow in any direction, so locating the leak is less of an exact science. Thus, it may take some special attention or an experienced roofing professional. As you look for leaks, you should always remember that the leak won’t necessarily flow where you think it should go, so you’ll have to be patient as you try to locate it.

Finding a leak is often a challenge when dealing with a flat roof. Flat roofs tend to develop leaks more easily because the water sits on the roof longer than it does on a pitched roof, which means the water can more easily go in places that it shouldn’t. This problem is especially profound in poorly installed flat roofs. However, flat roofs can last for many years when installed well and maintained by owners, which is why it’s vital that you know how to take care of your roof and address any leaks before they get worse. With these simple steps, you can find your flat roof leak without too much worry.

How The Inside Helps You Find The Leak

The leaks in your flat roof can be up to twenty feet from where you see the leak’s evidence, and the water can then travel through each of the roof layers. There may not necessarily be external damage, but the water can still be within those inner layers causing damage and leaking. Thus, the leaks in flat roofs can be incredibly covert.

The first thing you want to do when finding a leak on a flat roof is to go inside the building and look for evidence of water damage on the ceiling or in the attic. If water is dripping in your house, a leak is likely. While water dripping in your home is a blatant sign of a roof leak, there are many other signs that you can look out for before any leaking like that occurs. Water staining is one of the most significant indicators that you have a roof leak. Ceiling discoloring on your building’s highest floor often means that you have an issue with your roof. Thus, even small stains can indicate a problem with your roof, and you should always pay careful attention to where you find discoloration.

While water stains are the most obvious, but they are far from the only sign of leak you might experience. Because mold needs water to grow, if you notice that you have mold growing on the top floor of your building and don’t have a different cause for the growth, mold is a red flag and should always cause you to investigate your roof further, but we are not experts on mold, so you’ll have to seek professionals in that area to handle the mold itself. When you have leaks, you may also see bubbles in your walls or ceiling. Water can gather behind the paint and push the paint out to form bubbles. This collection of water is a strong sign that something is wrong, and it can often suggest a problem with your roof.

Identifying Signs Of Damage From The Ground

You’ll also have to look for exterior signs of water damage because there are many signs you may spot on the outside of your roof. When you check, do so on a dry day, or else it will be hard to identify leaking versus normal wetness. Just as you may see mold inside your building, you may also spot mold outside your building. Gutter and drainage issues are another sign that you may have problems with your roof. When you have rusty, bent, or otherwise broken gutters, your roof may struggle to drain excess water, which can then cause leakage. Thus, ensuring your gutters are in good shape is a vital part of keeping your roof healthy.

Looking at the various parts of the roof is also advisable. For example, the roof’s flashings— the parts of the roof that connect the roof membrane to other elements such as chimneys or plumbing stacks—can have broken or overlapping areas that indicate a problem. Finally, look for low spots on your roof. You can find these spots by spotting puddling water after rain, or when your roof is dry, rings of dirt often indicate low spots. These low spots can cause damage as water collects over time and weakens the roof. Remember that you won’t always see outward signs of roof damage, but being aware of problem areas will keep you more vigilant about the well-being of your roof.

Once you have found evidence of a leak, you should follow water stains to the leak’s loosely estimated source. Under the roof deck, trace the path of the stain to find the source. Doing so should provide you a rough estimate of where to head next. With flat roofs, the leak can be several feet away from where you measure the stain, which means this is a fair starting point for identifying the leak. While this step is pretty straightforward, it is critical because it channels your focus and makes finding a leak less overwhelming.

Remember that while water paths are less predictable in flat roofs, no roof is completely flat, and they all have at least a bit of a slope. The direction of that slope is also helpful to observe as you go through these early steps because it can give you more information about where the water will go.

Inspecting The Leak From On Top Of The Roof

Following the water stain, you can measure the distance between the two walls to the stain. These measurements will show you where the leak could be on your roof. This method is less precise in flat roofs, but it gives you a place to look when otherwise you might feel completely lost. Then, using the distance between the two walls as a guide, you can measure out the same spot on the roof. This spot shows you where to begin the next part of your investigation work.

In the next step, you will need to try to find the leak based on your measurements. Go to the spot on the roof that you measured out and see if you can find any issues in that area of the roof. As you’ve learned, the leak isn’t be where you measured it precisely. With that in mind, you should check the seams and penetrations in the areas that you measured. You can poke at the seams with your fingers to ensure their seal is tight. Look at the radius around the point you measured and test that space before straying to other roof areas. When you have tried that first area out, you can go back to the drawing board and look for other problem areas to see if you can find more conclusive evidence.

You’ll also have to look for other leaks. While it would be nice if a roof could have just one leak at a time, you may have multiple leaks, making it even harder to interpret the data you’ve collected. Because there can be several leaks at once while you’re on your roof, you should evaluate other areas and give them a look over to scout out other potential leaks. If you see any exterior damage, assess it further. By keeping an open mind to the possibility of multiple leaks will save you time and energy. You might as well be thorough when you’re already on the roof!

What To Do If You Can’t Find The Leak

While high-power moisture meters can also show you where water is pooling and help you verify leaks, many people must rely on thorough inspections and checking every detail to find leaks. Once you have found where you think your leaks are, you’ll have to verify those leaks. The source of the leak is often a loose seam in the rubber, a roofing vent pipe leak, a puncture, or poorly installed flashing, so keep those areas in mind as you verify the leaks. Looking for abnormalities can help you see where the roof’s vulnerable points are and help confirm suspicions you have about where the leaks are.

You can use the hose test to test a leak on your roof, but only as a last resort. When you use this test, you’ll want to go on your roof with your hose. Carefully direct water to the area you suspect contains the leak and have a second person tell you the results. This method can help you determine a more precise location of your leak that requires less guessing. Complete this task backward from the drains or gutters. When you use this method, you should be patient because it can take several minutes before the water becomes evident indoors. If the leak isn’t where you thought it would be, this test can help you guess and check several other locations until you find the right one. Of course, this method is only advised if you have exhausted all other DIY options because spraying a leak with more water can easily cause more damage in the process. Patience is the key to this method, and if you don’t have patience, it won’t be much help.

At RoofPRO, our team of skilled contractors is trained to identify the source of leaks and provide effective solutions to fix them, ensuring the longevity and integrity of your roof. When DIY efforts fall short, RoofPRO is the trusted roofing contractor to call in the greater Maryland area. Our contractors work within a 60-mile radius of our office location in Severn, MD, so we can help businesses throughout the state, including:


Safety And Finding Roof Leaks

Don’t be discouraged if it takes several attempts to find the leak’s location. You can continue to search for any irregularities and see if they are causes of leaks. Looking for leaks can feel like being a detective, so don’t give up after just one miss. If all else fails, you can always seek the guidance of professional roof inspection to find even the trickiest of leaks.

When trying to find a roof leak, you must also remember to maintain proper safety precautions. It’s especially critical that you are mindful of your safety on a flat roof because more people fall off flat roofs than sloped roofs because they feel safer on flat roofs and are less cautious. Always know where you’re walking. You should never walk backward on a roof for one, and when it is winter, you should still watch out for black ice. By being more aware of yourself and the conditions of the roof, you will be safer.

Finding a leak on a flat roof can be an immense challenge, especially for people doing it for the first time. Flat roofs, for all their benefits, are a challenge to navigate. Yet, flat roof leaks are not impossible to find. It becomes easier to find these leaks when you put the methods listed here into practice. Knowing how to check your roof for leaks is a skill that prevents roof damage from worsening. It’s also vital that you maintain your roof and catch leaks before they get worse to have fewer repairs in the future. Looking for leaks can be time-consuming and frustrating, but it can save you a lot of stress in the long run.


Article Updated on June 13, 2023.