Flat roofs have long been a popular choice for domestic and commercial buildings in the UK, particularly when it comes to extensions and garages.
While once considered a less durable option than a traditional pitched roof, modern materials and installation techniques have made flat roofs more reliable and longer lasting than ever before.
In this article, we’ll draw upon the expertise of flat roofing specialists ARK Roofing, as we explore the benefits and drawbacks of flat roofs, how they can be made watertight, and the best ways to maintain and repair them when needed.
Why Choose a Flat Roof?
Flat roofs are an appealing choice for many homeowners and builders, especially when working on single-storey extensions, garden rooms or garages. Here are some of the key advantages:
1. Cost-Effective Construction
A flat roof is generally cheaper to install than a pitched roof. The materials are typically less expensive, and the simpler structure requires less labour and time to construct. This makes it an ideal choice for projects where budget is a major consideration, such as home extensions or detached garages.
2. Ease of Installation and Servicing
Because of their design, flat roofs are relatively straightforward to install. The process involves fewer components than a pitched roof, and maintenance tasks such as gutter cleaning or checking seals can usually be carried out safely with minimal equipment.
This accessibility also makes repairs simpler and more affordable.
3. Space Efficiency and Design Flexibility
A flat roof allows for a clean, modern aesthetic that can complement a range of architectural styles. It also provides practical benefits — for instance, it can serve as a base for a roof terrace, solar panels, or even a green roof.
4. Doesn’t Block Light
One major advantage of a flat roof, particularly on extensions, is that it doesn’t obstruct light from reaching upper windows of the main property or neighbouring buildings. This can make it easier to secure planning permission and helps maintain natural light within the home.
The Drawbacks of Flat Roofs
While flat roofs have many benefits, they also come with certain challenges that need to be managed.
1. Waterproofing Challenges
Unlike pitched roofs, flat roofs do not naturally shed rainwater. Without proper drainage, standing water can lead to leaks and damage over time.
Historically, this was one of the biggest drawbacks of flat roofing, but modern materials and techniques have made significant improvements in this area.
2. Maintenance Requirements
Flat roofs require regular maintenance to ensure they remain watertight. Leaves, debris and moss can block drainage outlets, leading to pooling water.
Regular inspections are necessary, especially after periods of heavy rain or snow.
3. Shorter Lifespan
Although modern flat roofs can last for several decades, they generally have a shorter lifespan compared to pitched roofs. The average flat roof might last between 20 and 40 years, depending on materials and upkeep.
However, with proper maintenance and high-quality installation, this can be extended significantly.
Modern Waterproofing Materials and Techniques
The reputation of flat roofs has improved dramatically thanks to advances in waterproofing technology. Here are some of the most popular modern materials and methods used today:
EPDM Rubber Roofing
EPDM (Ethylene Propylene Diene Monomer) is a highly durable synthetic rubber membrane. It’s resistant to UV radiation, temperature fluctuations, and general wear and tear. EPDM roofs are often supplied in large sheets, reducing the number of joins (and therefore potential leak points).
GRP Fibreglass Roofing
Glass Reinforced Plastic (GRP) roofs are seamless and strong, providing an excellent waterproof barrier. They’re particularly suitable for garages and small extensions and can be finished with a non-slip topcoat if access is required.
Modified Bitumen (Torch-On Felt)
Traditional felt roofing has evolved into modern torch-on systems using layers of modified bitumen. These layers are heat-bonded to create a strong, flexible and waterproof finish. It remains one of the most cost-effective flat roofing materials available.
Liquid Roofing Systems
Liquid-applied membranes, such as polyurethane or acrylic coatings, are another modern innovation. These are painted or sprayed on to create a continuous waterproof seal, ideal for complex shapes or refurbishment projects.
Improved Drainage and Insulation
Today’s flat roofs are designed with a subtle slope (known as a fall) to encourage water runoff, along with integrated drainage outlets. Paired with high-performance insulation, this makes them far more efficient and weather-resistant than older systems.
Repairing a Flat Roof
Even with modern materials, a flat roof may eventually require repair. Common issues include small cracks, punctures, or damage to the waterproof membrane.
- Patching: Small areas of damage can often be patched using compatible materials such as EPDM repair tape, liquid sealant, or GRP resin.
- Resealing Joints: Over time, flashing or joints may degrade and allow water ingress. Reapplying sealant or replacing flashing can resolve the problem.
- Overlaying: In some cases, a new membrane can be applied directly over the existing roof, saving time and cost compared to a full replacement.
- Full Replacement: If the roof structure has deteriorated or widespread leaks occur, it may be more cost-effective to replace the roof entirely with a modern system.
Conclusion
Flat roofs have come a long way from their early reputation for leaks and short lifespans. With today’s advanced materials like EPDM, GRP and liquid membranes, they can provide a durable, cost-effective, and visually appealing solution — particularly for extensions and garages. While they do require regular maintenance to stay in top condition, the ease of access and simplicity of design make them a practical choice for many homeowners.
Whether you’re adding space to your home, building a new garage, or refurbishing an older roof, a well-designed and properly installed flat roof can offer excellent long-term value and performance.
