What Are the Best Flat Roofing Systems?

Various flat roofing systems are available, from single-ply membranes to traditional felt roofing and eco-friendly green roofs, each with its own benefits and considerations.

Flat roofs, with their nearly level surface and slight slope for drainage, are typically seen on commercial and industrial buildings. Due to their inexpensive construction and easy installation, they’re becoming increasingly common across residential properties in the UK. But what are the best systems for your flat roof?

Why have flat roofs grown in popularity in the UK? 

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Flat roofs have grown in popularity in the UK for various reasons. Their modern aesthetic appeal fits well with contemporary architectural styles. Flat roofs offer more usable outdoor space, such as rooftop gardens or terraces, which can be especially valuable in urban areas with limited space.

Flat roofs can be more cost-effective than pitched roofs, requiring fewer materials and less labour. They also provide easier access for maintenance and installation of solar panels or other eco-friendly features.

How common are flat roofs? 

Flat roofs are common in the UK, with 7 in 10 UK properties having a partial flat roof, particularly in urban areas and on properties with modern architectural designs. While pitched roofs are still prevalent in traditional housing styles, flat roofs have gained popularity in multi-story and commercial buildings, apartment complexes, and contemporary residential properties. 

When were flat roofs first used?

Flat Roofing Systems

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​​Flat roofs can be traced back to some of the earliest civilisations, usually in warmer climates. Widespread use in Europe started in the 19th century when waterproofing became more practical. Flat roofs became more common during the 20th century, especially in commercial and industrial buildings. 

The mid-20th century saw a surge in their use in residential construction, thanks to the modernist architectural movement. Over time, there have been improvements in materials, construction techniques, and regulations to address issues like drainage and insulation, keeping flat roofs relevant in contemporary UK architecture.

What are the top 5 flat roofing systems?

The cost to replace a flat roof varies depending on size and use, but new residential flat roofs tend to cost between £1,000 and £8,000. So, choosing the best type of flat roofing system is crucial to ensure it is waterproof, safe and protected from the elements to avoid a costly replacement.

1. Single-ply membrane roofing: 

Flat Roofing Systems

source: roofixservices

Single-ply membranes are durable, flexible, and resistant to UV radiation and weathering. They can be obtained from single-ply membrane manufacturers like Alwitra. Simple and safe to install, with no naked flames, the synthetic rubber is glued to clean roof decking. 

A single layer of synthetic polymer material, such as thermoplastic polyolefin (TPO), polyvinyl chloride (PVC), or ethylene propylene diene monomer (EPDM), is applied to the roof substrate. Single-ply membranes provide long-lasting protection and cost-effective waterproofing to flat roofs.

What are the key features?

  • Durability: Strong and elastic, ideal for roofs subject to expansion/contraction.
  • Lifespan: Up to 50 years.
  • Installation: Easy installation; no open flames required.
  • Versatility: Available in various colours for aesthetic customisation.

2. Modified Bitumen:

Flat Roofing Systems

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Modified bitumen is a flat roofing material incorporating added polymers, such as styrene-butadiene styrene (SBS), to improve its performance characteristics. The bitumen is applied to the felt in a molten state, and then a gas torch is used to heat it and fuse it to the roof deck. It is more expensive than a single-ply but is quick and easy to repair.

What are the key features?

  • Durable: Modified bitumen roofing is a durable material that lasts up to 30 years.
  • Waterproof: Modified bitumen roofing is a waterproof material that will protect your roof from the elements. If one layer fails, the additional layers ensure the roof is protected from water damage.
  • Flexible: Modified bitumen roofing is flexible and can accommodate the movement of the roof deck.
  • Installation: Whilst it takes longer to install than single-ply, modified bitumen roofing is relatively easy to repair.

3. Traditional flat roof felt:

Flat Roofing Systems

source: alpharoofingservices

Traditional flat roof felt is a cost-effective waterproofing solution. It’s made from a bitumen-based material reinforced with a layer of polyester or fibreglass. The felt is applied to the roof in layers, with each layer being overlapped and sealed.

What are the key features?

  • Cost-effective: Traditional flat roof felt is one of the most affordable flat roofing materials.
  • Durable: Traditional flat roof felt is durable and lasts up to 25 years.
  • Waterproof: Traditional flat roof felt is a waterproof material that will protect your roof from the elements.
  • Easy to install and repair: Traditional flat roof felt is relatively easy to install and repair.

4. Green flat roof:

Flat Roofing Systems

source: toplineroofing

Green roof systems are growing in popularity, with building owners looking to be environmentally friendly and architects providing an attractive look to commercial and residential projects. A green flat roof is a living roof consisting of a layer of vegetation placed on a rooftop. It offers several benefits, including:

  • Improved air quality: Green roofs help enhance air quality by absorbing pollutants and releasing oxygen.
  • Reduced energy costs: Green roofs can help to reduce energy costs by insulating the roof and reducing the urban heat island effect.
  • Increased biodiversity: Green roofs provide habitat for various plants and animals, which can help increase biodiversity in urban areas.
  • Improved stormwater management: Green roofs can help to manage stormwater runoff by absorbing rainwater and releasing it slowly, which can help to reduce flooding

5. Flat Roof Decks:

Flat Roofing Systems

source: mydecorative

Flat roof decks are made from various materials and installed on accessible flat roofs, typically accessed by a staircase or another floor. They provide additional usable space and can increase a property’s value by creating a functional outdoor area. In London, estate agents estimate a flat roof deck terrace can add 10% to 25% to a property’s value.

What are the key features?

  • Usable space: This creates an additional outdoor living area on the roof.
  • Durability: Can be made from durable materials like aluminium or composite decking for heavier use.
  • Installation: Proper structural assessment and preparation are required before installation.

What are the benefits of having a flat roof? 

Here are the top 3 benefits of having a flat roof…

  • Space utilisation: One significant advantage of flat roofs is their ability to provide additional usable space. This space can be utilised for various purposes, such as creating rooftop gardens, outdoor lounges, or installing solar panels – although this will require additional mounting equipment. Flat roofs offer valuable opportunities for expanding living or recreational areas in densely populated urban areas with scarce land.
  • Cost-effectiveness: Flat roofs typically require fewer materials and less labour than pitched roofs. The simplicity of their design and construction process can lead to cost savings for both residential and commercial building projects.
  • Easy access and maintenance: Flat roofs offer convenient access for maintenance on commercial buildings and homes. This accessibility translates to easier upkeep, potentially preventing costly repairs in the future.

What are the issues with having a flat roof? 

Flat Roofing Systems

source: buildingtalk

Flat roofs can have their share of issues that owners or prospective buyers should know. Leaks can be a common headache, especially since water doesn’t naturally drain away like on sloped roofs—a key reason why choosing the best flat roofing system is crucial. 

  • Flat roofs can also become breeding grounds for mould and fungus, leaving unsightly marks and potentially harmful conditions. 
  • Water pooling, whether from rain or snow, can lead to further damage, including cracks that compromise the roof’s integrity. 
  • Even the angle of the roof and the flashing around its edges can cause trouble as the materials expand and contract with temperature changes.

So, to enjoy the benefits of a flat roof, you must ensure it’s protected.

Final thoughts 

There’s a diverse range of flat roofing system options, each with benefits and considerations. From the durability and protection of single-ply waterproofing to the eco-friendliness of green roofs, there’s a solution to fit every need, preference and budget. Despite their challenges, such as drainage issues and the potential for leaks, flat roofs continue to grow in popularity in the UK due to their modern aesthetic appeal, space utilisation potential, and cost-effectiveness.

Moreover, advancements in materials and construction techniques continually improve the performance and longevity of flat roofing systems. For instance, the single-ply membrane detail provides enhanced durability and waterproofing capabilities. Additionally, innovations like flat roof decks offer opportunities to maximise usable outdoor space while adding value to properties.