01274 317 091 
Flat roofing systems are a common choice for many residential, commercial and industrial properties across the UK. For that reason, flat roof leak repair jobs can also be quite common too. On one hand, flat roofs offer clean lines, simple installation and a cost-effective roofing solution. This makes them particularly popular for garages, extensions, and larger buildings.
On the other hand, as with any roofing type, flat roofs are not immune to wear and tear. Over time, even the most expertly fitted flat roof may begin to show signs of water ingress. And those that are not expertly fitted are certainly more prone to flat roof leaking.
So at some point your garage, extension or commercial building may need a flat roof leak repair. If you already know what you are doing, you can find supplies for your flat roof in our shop. For more information on what you will need and what to expect, continue reading for our guide on how to fix a flat roof leak. This guide outlines what causes flat roofs to fail, how to spot the early signs, and how to approach repair work effectively using EPDM rubber roofing materials.
Early indicators of a leaking flat roof
Water damage on a flat roof can develop slowly but result in rapid deterioration once it takes hold. Spotting issues early is key to reducing long term costs.
Common early signs include:
- Discolouration or damp patches on ceilings or walls
- Warped or sagging roof decking, especially on older garages or extensions
- Persistent pooling of water in certain areas of the roof
- Mould or mildew growth inside the property
- Visible cracks, blisters or punctures in the roofing membrane
Being proactive can help avoid costly structural repairs. If any of the above signs of your flat roof leaking appear, it’s best to investigate without delay.
Leading causes of why flat roofs leak
Many factors can contribute to a flat roof leaking and it’s often a combination of issues, rather than a single cause.
Aged roofing systems
Over time, all roofing materials begin to degrade. UV exposure, temperature fluctuations and general weathering will eventually compromise even well maintained flat roofs. If your flat roof is over 20 years old, replacement may be more cost effective than ongoing repairs.
Inadequate drainage
Flat roofs should have a slight fall to ensure water drains properly. Where this pitch is missing, or the structure has shifted over time, ponding water becomes a concern. If this is left unresolved, standing water will compromise the integrity of the roof covering. For more information on flat roof waterproofing, check out our blog!
Faulty installation
Poor workmanship is a major reason why many flat roof leaks occur. A lack of attention to joins, seams and detailing around any roof penetrations can create weak points where water easily enters.
Thermal movement and material failure
Older materials like oxidised bitumen lack flexibility. As temperatures rise and fall, these rigid surfaces crack or blister. Modern alternatives like EPDM rubber offer far greater movement tolerance, making them ideal for our variable UK climate.
Flashing defects
Roof flashings seal the perimeter of a roof and prevent moisture ingress where the roof meets walls or edges. Metal flashings, such as lead, expand and contract with heat. Over time, this may cause gaps to form, providing an entrance for water.
Overlapping seams and delamination
Seams and overlaps in traditional flat roofing membranes often fail over time. Delamination is another common problem, especially in older multi layered systems. EPDM membranes, often installed in a single seamless sheet, avoid these issues entirely.
The Alvadac approach to flat roof leak repairs
Step 1: Diagnose the source
Carry out a thorough roof inspection. Focus on weak spots such as drainage points, joins, upstands and areas around vents or skylights. A garden hose can help simulate rainfall to track down where water enters.
In cases where the cause is unclear or damage appears extensive, it’s advisable to consult a qualified flat roofing specialist. This is especially true if structural issues are suspected.
Step 2: Prepare the surface
The surface must be cleaned and dried before any repair work begins. Use a stiff brush or pressure washer to remove dirt, moss and debris. If you’re working with EPDM membranes, we recommend using an EPDM specific membrane cleaner to remove oils and contaminants and ensure strong adhesion of repair products.
Step 3: Repair with EPDM rubber roofing systems
At Alvadac, we supply a full range of EPDM membranes and accessories designed specifically for durable, long lasting flat roof leak repairs. EPDM rubber is the preferred material for its flexibility, weather resistance and ease of installation.
Key benefits include:
- Seamless application
- Resistant to UV and thermal movement
- Long lifespan (often over 30 years)
- Low maintenance requirements
For small repairs, our EPDM patch kits and adhesives can seal cracks or minor tears. For larger jobs, full re-roofing with a single-piece EPDM sheet ensures no joins or overlaps. This dramatically reduces future leak risks and further flat roof leak repairs.
How to maintain your flat roof
A properly maintained flat roof should serve you well for decades. Follow these best practices to keep yours in top condition.
- Conduct regular inspections (spring and autumn are ideal)
- Clear debris regularly to prevent blocked outlets
- Check flashings and seals after storms or high winds
- Reseal any exposed joints as needed
- Replace damaged insulation or roof boards promptly
An EPDM membrane system, when installed professionally and checked periodically, is one of the most effective ways to prevent recurring flat roof leaks.
All your flat roof leak repair needs catered for by Alvadac
At Alvadac, we supply and install premium EPDM rubber flat roofing systems for homeowners, developers and businesses across Yorkshire. We offer both the products and the expertise to repair, replace, or upgrade your flat roofing system with confidence.
- Browse our EPDM supplies for DIY repairs or full installations
- We offer flat roof installation to ensure long lasting professional results
- Contact us with enquiries or advice on flat roof leak repairs
If you found this blog helpful you should also have a read of our other post – Your Go-To Flat Roof Waterproofing Guide.