A flat roof is an aesthetically pleasing and functional system – until it starts to leak. A leaking flat roof is more than just an inconvenience, it’s a disaster waiting to happen. Even a tiny roof leak can lead to structural deterioration, mold and mildew growth, and expensive repairs. Property owners or managers who notice water stains on their ceilings, peeling paint, or unexplained moisture should act fast to prevent further deterioration.
But the good thing is that most roof leaks start small and sealing them early can prevent major issues, ensure long-term protection, and extend the life of the roof.
In this guide, we’ll walk you through effective methods to seal leaks in flat roofs so your home or building remains protected and dry.
Why A Flat Roof Is More Vulnerable To Leaking
Flat roofs are designed with a slight pitch to facilitate water drainage. However, time, wear and tear, weather conditions, and other factors can lead to leaks. Common causes include:
- Ponding Water: Water that remains on the roof for extended periods can degrade roofing materials.
- Membrane Damage: Cracks, blisters, or punctures in the roofing membrane can allow water infiltration.
- Flashing Failures: Improperly sealed or deteriorated flashing around roof edges, vents, or skylights can be entry points for water.
The small slope of flat roofs leads to slower drainage compared to steeper roofs, making regular inspections for damage and ponding water crucial.
Steps to Seal a Flat Roof Leak
Here is a quick action guide on how to locate and seal a leaking flat roof:
Safety First
Though working on a flat roof is much less risky than working on a pitched roof, basic precautions are still important. Before starting to repair your roof, think about your safety. For example, use appropriate footwear to prevent slips and avoid working on the roof during adverse weather conditions. However, this not only means being careful, you also need to have the right tools before you start. Depending on the type of flat roof you have, you might need a patch, sealant, gloves, a utility knife, and a safety harness.
Inspect the Flat Roof for Leaks
Finding the exact location of a leak can be tricky. Water often travels before dripping down into your building, making it seem like the issue originates from an entirely different spot. The best way to inspect a flat roof is on a dry day. Walk carefully across the surface, looking for cracks, punctures, blistering, or standing water. Pay close attention to areas around vents, chimneys, and seams where different roofing materials meet. If there’s an apparent crack or hole, that’s often the culprit. If not, the leak might be underneath the roofing membrane.
If you still cannot find the exact source, calling a professional contractor for help is important.
Once the leak is found, the next step is selecting the best sealing method. There are different approaches depending on the extent of the damage and the type of roofing material in place.
Choose the Appropriate Repair Method
The best repair method depends on the severity and type of damage:
Use Roof Sealant for Small Leaks
For minor leaks, roof sealant is a quick and effective solution. A good quality sealant forms a waterproof barrier over cracks and small holes, preventing further damage due to water intrusion. Before applying sealant, clean the affected area thoroughly. Dirt, debris, and moisture can prevent proper adhesion. A soft brush and a mild detergent solution work well for removing grime.
Here is what you need to do after drying the surface:
- Apply the sealant generously over the damaged area using a putty knife or a trowel.
- Silicone or polyurethane-based sealants are ideal for their flexibility and durability. They expand and contract with temperature changes, ensuring a long-lasting fix.
- Once applied, allow sufficient drying time before exposing the roof to rain or moisture.
Aren’t sure which sealant is the best for your flat roof? Read our guide: 6 Top-Rated Flat Roof Sealants of 2024
For Larger or More Extensive Roof Leaks
For larger leaks or areas with visible damage, a more robust repair method is needed. Roofing fabric combined with an elastomeric coating provides superior protection against moisture intrusion. This method is particularly effective for flat roofs with modified bitumen, EPDM, or TPO.
To begin, clean the area around the leak thoroughly. Apply a generous layer of roof coating over the damaged section, then embed a piece of roofing fabric into the coating. Using a roller, press the fabric down to eliminate air bubbles and ensure full adhesion. Once the first layer sets, apply an additional coat over the top for maximum durability. This method creates a reinforced, watertight barrier that extends the lifespan of the roof.
Note: This method requires a thorough knowledge of roofing materials. If you do not have experience patching a flat roof, it’s best to wait for professional help.
How To Address Seam and Flashing Leaks
Seams and flashing are common weak points on a flat roof. Over time, the sealant used around these areas can deteriorate, allowing water to seep in. To fix leaks along seams or flashing, use specialized roofing tape or liquid flashing sealant.
Roofing tape, made from butyl rubber or similar materials, provides a fast and effective seal. Clean the surface around the leak, peel off the backing, and adhere the tape to the leak. For added protection, apply a layer of sealant over the tape to create a seamless bond.
Liquid flashing is another excellent option, especially for complex areas where traditional patches may not adhere well. Apply a thick layer over the problem area and smooth it out with a brush. Once cured, it forms a flexible, waterproof seal that withstands extreme weather conditions.
How To Prevent Future Leaks In Flat Roofs
A flat roof needs more than just fixing leaks when they happen – it needs regular care to prevent future problems. Here are the key ways to keep your flat roof leak-free for years to come:
Regular Inspections & Cleaning
Don’t wait for leaks to show up inside your building. Make roof inspections a habit, especially after storms. Clear off any debris like leaves, branches, or dirt that could trap moisture and damage your roof over time. Standing water is your roof’s enemy – check that drains are clear and water isn’t pooling anywhere. A clean, well-maintained roof can last years longer than a neglected one.
Protective Coating Systems
Think of roof coatings as your first line of defense. Elastomeric coatings create a waterproof shield across your entire roof, sealing up small cracks and moving with your roof as it expands and contracts. Plus, reflective roof coatings keep water out while bouncing back the sun’s heat, which can lower your cooling bills and protect your roof from UV damage. A roof coating is an investment that pays off in both protection and energy savings.
When to Call a Professional
As we said, the earlier you identify the leak, the easier it is to fix. While you can seal minor leaks with DIY methods, it’s always recommended to call a professional roofing contractor. If the damage is extensive, the roof is aging, or previous repairs have failed, a full assessment from a roofing expert is the best course of action.
At A. Fricker Roofing and Waterproofing, we specialize in flat roof repairs and replacements. Our team is dedicated to providing expert solutions tailored to each building’s needs. If you suspect a leak in your flat roof, don’t wait until it worsens. Contact us today at (918) 402-7167 for a comprehensive inspection and reliable repair service.
