If you have a flat roof, you’re likely well aware of the frustration that leaks can cause. Flat roofs are more susceptible to leaks than sloped ones, often needing extra care and maintenance to stay in good shape. In this article, we’ll look at the common reasons flat roofs leak, ways to prevent them, and how to fix any damage before it worsens.
Table of Contents
- Reasons for a Flat Roof Leak
- Age
- Temperature Changes and Solar Gain
- Movement in the Structure
- Blisters
- Delamination
- Poor Design and Detailing
- Poor Workmanship
- Why Flat Roofs Leak: In Summary
- How to Prevent Flat Roof Leaks
- Planned, Proactive Maintenance
- Good Design
- Appropriate Repair and Replacement
- Vulnerable Areas of Flat Roofs
- Damaged Roofing Membranes
- Open or Damaged Flashing
- Blisters or “Bridging” in the Roof Membrane
- Skylights
- Debris
- Ponding
- Conclusion
- FAQs about Leak Investigations
- About Integritest
Reasons for a Flat Roof Leak
There are many reasons for a flat roof leak; here, we have listed 7 of the most common:
1. Age
Over time, all roofs age, and flat roofs are no exception. As your roof gets older, the materials that make up the membrane start to break down. For example, many roofs built in the 1960s used bitumen-based membranes that had a lifespan of just 20 years. By now, these roofs are well past their expected life, therefore cracks, splits, and leaks are almost inevitable.
Modern roofing materials, like elastomeric membranes, last much longer—around 30 years or more—but even these eventually reach the end of their life. If your flat roof is nearing or has surpassed its expected lifespan, it’s time to start thinking about repairs or replacement.
2. Temperature Changes and Solar Gain
Another reason flat roofs can develop leaks is due to temperature fluctuations. The roofing membrane is exposed to the sun’s heat, which causes it to expand during the day and contract at night. Older materials, such as bitumen, can’t cope with these temperature changes and often crack or split under the stress.
Solar gain, where the roof gets overheated due to the sun, can also exacerbate this issue. If your roof membrane is made from traditional materials, it’s especially vulnerable to these temperature fluctuations. The solution is to consider upgrading to modern materials designed to handle such stresses more effectively.
3. Movement in the Structure
Buildings naturally expand and contract as the temperature changes. If your flat roof isn’t designed with enough movement allowances or expansion joints, the roof membrane can be stretched, causing splits and cracks. This is especially common in older flat roof designs.
Today’s roofing systems take these movements into account, but if your flat roof wasn’t built with this in mind, it may need extra reinforcement or a new design to prevent leaks caused by structural shifts.
4. Blisters
Blistering is another frequent cause of leaks in flat roofs. These blisters or bubbles occur when moisture trapped beneath the roof membrane turns into vapour, creating pressure. The membrane tries to expand to release this pressure, but over time, it may tear or rupture, letting water seep through. Blisters can develop for several reasons, such as improper installation, insufficient drying during installation, or condensation between layers. Once a blister appears, it’s important to address it promptly to prevent further damage.
5. Delamination
Delamination occurs when the layers of the roofing membrane start to separate. This usually happens when moisture gets between the layers or when the membrane isn’t properly installed. As the layers separate, the roof loses its integrity, and water can begin to infiltrate, leading to leaks.
If you notice a roof membrane starting to peel or lift, it’s essential to address it quickly to prevent further deterioration and water damage.
6. Poor Design and Detailing
Sometimes, the reason for a flat roof leak isn’t due to the roof material itself but the way it was designed. Poor design or detailing, such as inadequate roof slopes, poorly sealed flashings around penetrations, or poorly constructed up-stands, can lead to water pooling or seeping into vulnerable areas.
Flat roofs should always be designed with sufficient slopes to allow water to drain away. If your roof has poor drainage or ineffective detailing, leaks can occur in places you wouldn’t expect.
7. Poor Workmanship
No matter how high the quality of the material, poor installation can still lead to leaks. If the roofing system wasn’t installed properly, seams may not be sealed correctly, flashings may be poorly fixed, or the materials may not have been applied properly. It’s essential to choose a reputable, experienced contractor for any roof work to ensure the job is done right the first time.
Why Flat Roofs Leak: In Summary
In summary, flat roofs leak for several common reasons: age, temperature fluctuations, movement in the building structure, blisters, delamination, poor design, and poor workmanship. If you own a flat roof, it’s important to stay vigilant and catch any signs of damage early before they lead to expensive water damage inside your building.
How to Prevent Flat Roof Leaks
While some causes of roof leaks are inevitable, there are several steps you can take to reduce the risk of leaks and keep your roof in good condition:
1. Planned, Proactive Maintenance
The key to preventing leaks is regular roof maintenance. Inspections should be carried out at least twice a year, ideally before and after the winter months. This helps you catch any damage early and prevent small issues from becoming bigger problems. A good maintenance plan can also help you keep your roof warranty intact if it’s still covered.
2. Good Design
If you’re building or replacing a flat roof, ensure it’s designed with adequate slopes and drainage. A well-designed roof will prevent water from pooling and reduce the risk of leaks. Avoid cutting corners on design, as this can lead to problems down the line.
3. Appropriate Repair or Replacement
No roof lasts indefinitely, but with proper upkeep, it can last for many years. If your roof is nearing the end of its lifespan or has suffered considerable damage, it may be time to think about repairs or replacements. Be sure to select top-quality materials that match your roof’s specific needs and have the work done by a skilled professional. Our article on which flat roof material is best gives you useful information on some popular flat roof materials that will help you choose the correct material for your needs.
Vulnerable Areas of Flat Roofs
If you’ve noticed signs of a leak in your flat roof, don’t wait for the problem to worsen. Here are some of the most vulnerable areas on a low-sloped roof that should be checked regularly:
1. Damaged Roofing Membranes
Regularly inspect your roofing membrane for cracks, splits, and wear. Over time, even the best materials can degrade, so keeping an eye on their condition is essential.
2. Open or Damaged Flashing
Flashings around pipes, vents, and other roof penetrations can break down or become loose, causing leaks. Inspect flashing at least twice a year and repair if needed.
3. Blisters or “Bridging” in the Roof Membrane
Look for blisters or wrinkles in the membrane, especially in older EPDM roofs. These issues signal that your roof is near the end of its life and needs attention.
4. Skylights
Skylights are prone to leaks, especially as seals wear down. Regularly check the seals and lenses; replace them if they’re damaged or worn.
5. Debris
Debris, like branches or gravel, can puncture your roof membrane. Keep your roof clean and inspect for any damage caused by fallen items.
6. Ponding
Ponding happens when water stays on the roof for more than 48 hours after rainfall. Over time, this can damage the membrane and lead to leaks. It’s important to regularly check areas that are prone to ponding.
Conclusion
Flat roof leaks are common, but with the right maintenance, inspections, and repairs, you can keep your roof in top shape for years to come. Don’t wait for the leaks to get worse—act now and protect your property.
FAQs about Leak Investigations
How Do I Tell if My Flat Roof is Leaking?
Check for water stains on the ceiling, peeling paint, or signs of mould. Detecting issues early is crucial to avoiding serious damage. Routine inspections are the most effective way to identify leaks early on.
How Often Should I Inspect My Roof?
You should inspect your roof at least twice a year, especially before and after winter. Consider more frequent inspections if your roof is older or you’ve experienced severe weather.
Can I Fix a Leak Myself?
While homeowners can sometimes repair small leaks, a professional roofing contractor should always handle larger issues or structural damage. Always assess the damage carefully before attempting repairs. For more information visit our article on how to deal with flat roof leaks.
About Integritest
IntegriTest has a reputation for being professional, collaborative, precise and thorough in our inspections and testing. We are trusted by manufacturers, latent defect insurers, principal contractors, waterproofing contractors and estate management companies across the UK to perform our varied services.
Article written by Ben Flood
