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Flat Roof Waterproofing Solutions

A flat roof, by design, has a pitch of below 10° and therefore requires specialised roofing systems that differ from those typically used on pitched roofs.

At CARLISLE®, we provide comprehensive flat roof solutions for new builds and refurbishments. We offer a wide range of materials and services, for architects, designers, contractors and distributors. Discover all about making your flat roof watertight with a solution to suit your project sustainably.

For specific information click below or discover more on our service portal.

CARLISLE® Flat Roof Systems: Robust, Durable & Sustainable

CARLISLE® flat roof systems are the perfect solution for a robust, durable, sustainable, and ecologically safe roof. Our systems include a choice of waterproofing membranes, including EPDM, TPO, or Liquid Waterproofing, over thermal insulation and a vapour barrier layer for a complete solution with adhesives and primers compatible with each system.

We offer a wide range of materials and services for new builds and refurbishments of flat roofs.


  • Long-lasting waterproofing: Our membranes are designed to last for many years and can withstand extreme temperatures and are UV resistant. Our EPDM membranes have a service life of over 50 years. Our hybrid membrane RESITRIX® is 100 % bitumen compatible and thus is also ideal for the renovation of bitumen roofs. No additional separating layers are required.

  • Safe and easy installation: Our membranes RESITRIX®, HERTALAN®, and SURE-WELD®TPO waterproofing membranes are welded together using hot air, eliminating the need for naked flames. This significantly reduces the risk of fire, making it a much safer option for roofers and building owners. In addition to being safer, our membranes are also more durable and long-lasting than traditional roofing materials such as Felt, PVC, GRP, and Hot Melt. They are also resistant to a wide range of weather conditions, making them an ideal choice for roofs in all weather conditions.

  • Sustainable and ecologically safe: Our roofing membranes are made from sustainable materials and are permanently resistant to bird droppings, chemical emissions, and other environmental factors. They are also free of hazardous additives like heavy metals, halogens, and volatile softeners, making them an environmentally friendly choice. Our membranes don't release any harmful toxins in the environment.


  • Extended service life: Our EPDM membranes come with over 50 years of certified service life.

  • Safer installation: Our flame-free welding process eliminates the risk of fire. To mechanically fix the membrane we have an innovative CARLISLE® Induction Fixing method to achieve circularity in construction.

  • Durable and flexible: Our membranes are resistant to extreme weather conditions and do not lose shape for many years.

  • Sustainable and environmentally friendly: Our systems are made from sustainable materials and release no harmful chemicals or toxins into the environment.


  • Felt or bitumen overlay: We can overlay on existing felt or bitumen roofs with a new layer of waterproofing membrane to extend the roof's lifespan.

  • Waterproofing solution for any project: We offer a variety of roofing systems to choose from, including EPDM, TPO, and Liquid Waterproofing.

  • Green roof systems: We can install green roof systems, which provide several benefits, including insulation, water management, and increased biodiversity. Our EPDM membranes can be installed on numerous substrates and under all types of roof gardens and green roofs.

For any specific requirement or to get technical advice, contact our Technical Team.


Flat Roof Construction: Warm Roof, Cold Roof, and Inverted Roof

High-quality flat roof waterproofing is essential to permanently protect the building from water and moisture ingress. Our products are optimally suited to every flat roof. There are three kinds of flat roofs construction:


Warm roof construction

  • A ‘Warm Roof’ is where the insulation is on top of the roof deck, i.e. the roof becomes warm. This is a reliable and preferred method of construction and provides robust detail. It is easier to calculate and achieve the required thermal performance (known as U-Value) by installing the appropriate insulation thickness. Most flat roofs are today built as unventilated warm roofs. The waterproofing is installed as the top layer without an intermediate space directly over the insulation. An essential component of this build-up is a vapour control layer (VCL).

  • Warm roof constructions are more complex than cold roof constructions, but they offer a number of advantages. They are more energy efficient, they provide better insulation against noise, and they are less likely to suffer from condensation problems.

Cold roof construction

  • It's important to understand that cold roofs and uninsulated roofs are not the same thing. While uninsulated roofs lack any insulation, cold roofs actually have insulation underneath the roof deck between the joists. Typically, this insulation is made of a mineral wool material such as Rockwool. The waterproofing layer is then directly applied to the structural deck.

  • One thing to keep in mind with cold roof constructions is that they require proper ventilation of the void. However, they do offer the benefit of keeping the overall height of the building to a minimum. This can be particularly useful in situations where there are upstand height issues against an adjoining wall with window or door sills, or to comply with local planning restrictions.


Inverted roof construction

  • When it comes to roofing, inverted roofs are a smart choice for durability and strength. Unlike traditional warm roofs, inverted roofs feature a waterproofing layer applied directly to the roof deck, with insulation situated below. This construction style makes inverted roofs ideal for areas with high foot traffic, such as podium decks, terraces, and walkways. Additionally, inverted roofs are an excellent option for roofs that may face heavy snow loads. Choose an inverted roof for long-lasting protection and reliability.


Specify Your Flat Roof System Here

With the NBS Source, you can easily streamline your project specification process by directly adding products and generating 3D models through NBS Chorus and Autodesk Revit integrations. Additionally, you can conveniently download product information for future reference.

More about CARLISLE® Flat Roof Systems

To enhance your understanding of our flat roof systems and their potential benefits for your current roofing solution, we have compiled additional information below.

Flat Roof Membranes

  • One of the robust waterproofing membranes for Flat roofs is made from EPDM rubber, making them the ideal choice for protecting your flat roof.

  • They offer a seamless design as well as effectively deal with rainwater, high temperatures, flexing and protection against debris.

  • There is a range of EPDM rubber roof membranes to choose from, each with specific properties depending on the solution you need.

  • EPDM membrane installation on flat roofs can last for more than 50 years, requiring minimal maintenance during this time.

  • To ensure longevity and prevent issues like sagging, cracking, or blistering, we recommend using quality flat roof membranes from Resitrix or Hertalan as these products offer enhanced durability compared to lower-quality membranes.

Flat Roof Repairs

As mentioned above, flat roofs with EPDM rubber systems require very little maintenance and are extremely durable in comparison to other flat roof systems.

However, any roof is susceptible to damage from debris from nearby trees caused by high winds or even falling debris from nearby buildings. If you’re unfortunate enough to have damage to your EPDM flat roof, they are easy to repair using specific EPDM flat roof repair kits.

Whether you’re looking for a full roof replacement or just need to patch specific areas with fillers, coatings, or other flat roof repairs, our team of specialists can assist you with the best systems and kits for your project.


Get in touch with our sales team today to discuss the best options for you.

Felt Roofs

Felt roofs are an alternative to EPDM rubber flat roofs that were common with sheds and garages. However, waterproofing felt roofs is not as effective as using EPDM membranes as it will need replacing much sooner.


EPDM membranes can be calculated to offer exact measurements to your requirements, minimising wastage and saving you money in the long term.


Support for all stages of your project


Here at CARLISLE®, our commitment to good service means that we are always there to provide you with technical advice and assistance, from the initial consultation to on-site visits and inspections and even after the completion of your project, we are here for you.


Whether it's a new build or renovation, from roofing to building waterproofing our services are here to help you.

Our Services

  • Roof condition survey

  • Roof inspections

  • Detail drawing preparation

  • Preparation of renovation concepts (flat roof check)

  • Drainage calculation

  • Test Certificates

  • Wind upload calculations

  • U-value calculation

  • Product training courses & CPDs in our CARLISLE® ACADEMY

  • Installation instructions for installers

  • Delivery to the location of your choice, also direct to the site

  • Extended testing in our in-house test laboratory

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