A bespoke, and technically accurate, roof specification is essential for achieving the design intent of a roof. Roof specifications are also integral to the buildability, performance and longevity of a construction project.
Accurate roof specification is critical to the performance, lifespan and maintenance requirements of the whole building. Understanding the factors that can optimise roof specifications, aligned to the specific requirements and objectives of the project, can deliver cost and sustainability benefits.
A roof specification is much more than an off-the-shelf roofing system; it is a comprehensive guide outlining the materials, performance requirements, and installation methods needed for the project.
The detailed information provided by roof specifications ensures that the whole supply chain, including the manufacturer, architect, contractor and installer, are working together to deliver a roof that leverages the full functionality, durability and safety of the roofing system, and that it will achieve compliance with industry standards.
At CARLISLE®, we understand that each roofing project comes with its own set of challenges. That’s why our range of high-performance roofing materials have been developed to meet the needs of a huge array of construction projects and site environments; from warm roofs to green roofs.
In this roofing specification guide, we will:
Break down what a roof specification entails.
Outline considerations for selecting roofing materials for your project.
Explain why roofing specifications are so important.
Detail the technical support you can expect from CARLISLE® for roof specifications.
What Does a Roof Specification Entail?
Roof specifications are detailed instructions that define the technical requirements of a roof and detail the roofing system to be used, including all roofing materials and installation methods.
Acting as a guide for architects, contractors, building surveyors, and installers, roof specifications ensure that all roofing materials are chosen and installed to meet the highest standards of quality and performance.
By meticulously following the roof specification, construction delivery partners can ensure the roof build-up meets all mandatory building regulations, including the Building Safety Act 2023.
Installing the roofing system accurately to the roof specification also ensures that it will maintain its performance with local weather conditions, and provide a long service life, equal to or greater than the roofing system manufacturer’s warranty.
Key Components of Roof Specifications
There are several key components of a roof specification and all must be specifically tailored to the individual requirements of the individual roofing project. here are a few factors to consider:
Pitch: even flat roofs should be specified to a minimum fall of 1.80m.
Vertical surfaces: where there are vertical surfaces, such as upstands or parapet walls, the roof specification needs to consider the suitability of the chosen waterproofing materials.
Weather resistance: along with waterproofing performance, roof specifications should consider U/V resistance and resistance to wind uplift.
Detailing: some roofing systems include pre-formed roof details, while liquid waterproofing systems can be applied to the contours of any detail.
Compatibility: you must ensure that the roofing materials specified are compatible with the substrate or any existing roof covering and also with any additions such as green roof planting or rooftop plant.
Buildability: ease and speed of installation will affect the construction programme and the length of time it takes to make the building watertight.
Service life: a roofing system applied to manufacturer’s guidelines and roof specification will have a warrantied lifespan, and some systems have an anticipated lifespan in excess of the warranty.
Sustainability: the roof specification can contribute to the overall sustainability credentials of a project.
Choosing the right roofing materials is one of the most important aspects of roof specifications, because the materials selected must be suitable for the building type, weather conditions for the location, and the performance requirements for the built asset.
For example, the roof specification should include consideration of the weight of the building materials and whether the roof build-up will fall within the loading parameters for the structure. Popular roof specification options include:
EPDM membranes.
Single-ply roofing systems.
Cold-applied liquid waterproofing.
Bituminous roofing systems.
The roof specification should also address the need to enhance the building’s thermal performance with various types of insulation, and it should include all ancillary materials required for a successful roof build-up, such as vapour control layers (VCL), breather membranes, primers, and adhesives.
Here are some examples of roofing materials:
EPDM Roof Systems
CARLISLE®'s EPDM membrane, HERTALAN®, is a popular roof specification choice, as is the CARLISLE® RESITRIX® roofing system, which combines EPDM with a bituminous membrane in a unique single ply solution. Both of these roofing systems offer unparalleled durability, flexibility and ease of installation and waterproofing performance.
Every roof specification should carefully consider the suitability of all materials to ensure they meet the needs of the project from both a buildability and performance perspective.
The RESITRIX® hybrid EPDM and bituminous membrane is self-adhesive, which simplifies installation and ensures a secure, watertight bond. Meanwhile, HERTALAN® EASY COVER is an ideal roof specification choice for larger roofing projects, offering fewer seams and a robust waterproof barrier with excellent elasticity and an extended service life.
Request a free sample by clicking the button or explore the RESITRIX® and HERTALAN® ranges by clicking on the brands below.
Cold Applied Liquid Waterproofing Roofing Systems
Liquid waterproofing systems have become a popular roof specification choice and are particularly appropriate for roofs with complex detailing. They are also often used as an effective overlay for refurbishment projects, where the roof specification needs to ensure effective waterproofing of an existing roof without strip-out of the existing roofing material.
For instance, the ARBOFLEX® PU single component, cold-applied liquid waterproofing system from CARLISLE® provides superior protection against water ingress, while providing speed and ease of installation benefits. The cold-applied liquid waterproofing covers and cures rapidly, enabling the project team to make the building watertight quickly, while enabling complex details to be achieved with ease.
Thermal Insulation
Thermal insulation is a key part of roof specifications because it not only affects the energy efficiency, comfort, and environmental impact of the building, but is also a requirement for building regulations compliance.
A fabric first approach to constructing more sustainable buildings prioritises high performance insulation as part of the roof specification to help maintain a comfortable indoor temperature all year round. This reduces the operational costs and carbon emissions associated with heating and cooling, while also contributing to the overall sustainability of the building.
A roof specification usually describes the type of insulation needed. This includes details about the thickness of the insulation material, along with its R-value (thermal resistance) and K-value, which is also known as the Lambda value (thermal conductivity).
CARLISLE® supplies thermal insulation as part of roof specifications to enable a complete roof build-up with single source supply. The insulation provided by CARLISLE is compatible for use with all our roofing systems, including HERTALAN® EPDM, RESITRIX® and the ARBOFLEX® PU cold-applied liquid waterproofing system.
Roof specifications should be specific about the installation sequence for all roof materials, including breather membranes, VCLs, primers and adhesives, stipulating whether the insulation and waterproofing layers should be installed together as a warm roof or an inverted roof build-up.
Wind and Fire Resistance
Roof specifications must also address the roof’s ability to resist external forces, such as high winds and fire. The Building Safety Act 2023 requires that design, material selection, and installation practices used to build a roof prioritise fire safety and overall structural integrity.
Fire safety is a roof specification consideration for the completed building and also for the build phase of the project. RESITRIX® membranes are FM-approved, meaning they meet stringent industry standards for fire and wind resistance.
As none of CARLISLE®’s roofing systems require ‘hot works’ (i.e. the use of a flame to melt the membrane to fix it to the substrate, achieve laps, or secure terminations), this makes CARLISLE® systems safer to use and avoids the need for a ‘fire watch’ by the installation team following each day on site.
Wind resistance is also important, both during the build and after completion of the project. Wind uplift during the construction programme is a health and safety issue for those on site.
Following completion of the roofing project, the roofing system should resist damage or uplift from strong winds, and it is important that the roof specification considers maximum average wind speed and gust data for the height, position and location of the building, along with the installation method used.
For example, wind uplift can be a major concern in exposed areas, and specifying proper fastening methods or choosing mechanically fixed membranes can ensure the roofing system remains intact even in severe weather.
Installation Techniques
Correct installation is essential for a roof to perform effectively. Roof specifications should provide clear instructions on how to install the materials. They should consider factors such as roof pitch, techniques for forming laps, fastening methods, and terminations.
Correct installation according to the roof specification is critical to passing the roof’s final inspection and achieving the manufacturer’s warranty for the selected waterproofing system.
The roof specification should consider how the risk of installation defects or performance issues can be minimised with material selection. For example, HERTALAN® EASY COVER and RESITRIX® membranes are supplied in large sheets, which reduces the number of seams – the most vulnerable areas for water ingress - thereby lowering the risk of leaks.
Depending on the specific requirements of the project, these roofing systems can be fully adhered, mechanically fixed, or ballasted, with hot air-welded laps to seal the seams.
The Role of Roof Specifications in Sustainability
Sustainability is a critical measure of success for any construction project. Roof specifications play a key role in ensuring that roofing systems contribute to sustainable construction practices and built assets.
Circular sustainability is a positive roof specification goal, and recyclable materials such as EPDM can contribute to a circularity strategy. EPDM also has a low environmental impact during production.
Meanwhile, TPO roofing membranes, such as CARLISLE®’s SURE-WELD® waterproofing system, can be supplied in pale colours such as white and light grey, which reflect sunlight, countering the urban heat island effect and helping to reduce the building’s cooling needs and energy consumption.
Green roofs are another way in which roof specifications can contribute to the sustainability of a building. Green roofs are becoming more popular in urban areas, and require specific roof specifications to ensure that the waterproofing membrane is root-resistant and can withstand the weight of the growing medium.
CARLISLE® has a number of roof specification options for green roof specification, including the ARBOFLEX® PU cold-applied liquid waterproofing system, which is compatible with green roofs, providing a durable, root-resistant barrier that prevents water ingress while enabling plant growth.
Carefully choosing materials and methods that support energy efficiency and circularity results in a sustainable roof specification that not only meets performance standards, but also contributes to reducing the carbon footprint and environmental legacy of the building.
Why Roof Specifications Matter
Accurate roof specifications are vital for the success of any roofing project. They ensure that every element of the roofing system works together seamlessly to provide the best performance.
Detailed roof specifications ensure the completed project complies with all relevant building regulations, including the Building Safety Act 2023. This not only reduces the risk of expensive call backs or remediation, but underpins the safety, performance, sustainability and longevity of both your roof, and your building.
Whether you’re specifying a new build, refurbishment, or green roof project, having a clear roof specification tailored for your specific project is essential to achieving the best results from the roofing system.
More Information
Explore our service portal for helpful downloads, videos and installation instructions for our products or contact our expert team today on 01623 627 285.