Leaky Roof? Find the Source With These 6 Tips

Kristi Pahr
Written by Kristi Pahr
Updated December 22, 2021
Modern geometric house with patio
Photo: dglimages / Adobe Stock

Flat-out irritated over a leaky roof? Keep the elements outside where they belong

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No one likes to slosh through puddles, especially when inside their own home. Finding a leak in a flat roof can be a little tricky, but with some persistence, you can stop the drip and keep the outdoors where they belong.

How to Check a Flat Roof for Leaks

Roof leaks can be tricky to find. Just because you see water on your ceiling doesn’t mean the leak is directly above it, even in flat-roofed structures. In a sloped roof, water only runs one way—down. But since water always follows the path of least resistance, any deviation in a flat roof causes water to run. That might be low spots or trusses or even electrical or ventilation equipment. Water can run in any direction in a flat-roofed structure, making it a little more difficult to find the source of your leak. To suss out where your flat roof is leaking, follow these six steps and you’ll be high and dry in no time.

Follow these six steps, and you’ll be high and dry in no time.

1. Clear Your Roof of Debris

Clear your roof of all leaves, sticks, and other debris with a leaf blower or push broom. Debris could be covering problem spots on the roof, and ensuring a clear surface will make your leak hunt easier.

2. Check Your Flashing

Cement chimney on a flat roof
Photo: ArieStudio / Adobe Stock

Roof flashing is a material made of metal strips that cover gaps between the roof and chimneys, skylights, or other elements that require cutting a hole in the roof. Flashing is generally in two layers — an inner layer covers the wooden sub-roof material and an outer layer that serves as secondary protection. Over time flashing can become damaged or separated due to expansion and constriction of roof materials and allow water to seep through the cracks.

3. Check Seams and Plumbing Exhaust Collars

Any place where two sections of roofing come together will have a seam. Sometimes these seams spread apart, leaving space for water to enter the structure. Likewise, the collars surrounding plumbing exhaust pipes that exit the roof can become dislodged or damaged and leave open spaces between the pipe and the roof.

4. Check Old Patches

If the roof has leaked in the past, the patching material used to repair the leak might have degraded, allowing the source of an old leak to open back up to the elements.

5. Check for Low Spots

Rain water puddle on a flat roof
Photo: Luise123 / Adobe Stock

Low spots in the roof allow water to sit in puddles. If water stands on a roof for more than 48 hours, the roofing material can begin to degrade. If this happens repeatedly, the roofing material can degrade to the point that a leak forms.

6. Spray The Roof

With a water hose, wet down any questionable areas of the roof and check to see if the area of water damage inside is showing activity. If you’re still unable to find the source of the leak, systematically wet sections of the roof one at a time and check for evidence of water inside. This step could take up to several hours depending on the size of the roof.

What To Do About a Leak in a Flat Roof

Once you’ve located the source of your leak, you should call the roofing professionals who installed it. If it’s been less than 20 years since they installed it, your warranty could cover the repair. But if you attempt the repair yourself, your warranty might be void. 

Roofing repairs are fairly specialized, and the materials used in many flat roofs require special tools to fix. Check your roofing company or a different company if your warranty is no longer valid to see your options for repair. Restore any water damage quickly to avoid developing mold, mildew, or rot.

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