Technical Focus

HOW TO BUILD A RESILIENT ROOF

Carl Bailey, Regional Technical Manager for Elevate, part of the Holcim Group, discusses the urgent need to create resilient roofs, including the critical roofing components and the benefits of an EPDM membrane.

The need for resilient roofing has never been more important. As the impact of climate change takes hold, it is crucial that a roof protects against increasingly severe weather, including extreme temperature change, rain, hail and wind.

For the owners of public sector buildings and their local communities, roof resilience means less disruption to daily life. The risk of any roof damage is minimised, reducing potential costs and downtime, and enabling essential services provided by hospitals and schools to continue.

Another important driver for a resilient roof is futureproofing. If a building needs to extend or adapt, then it may have to accommodate new plant, service penetrations and equipment such as solar panels. A robust roofcovering should enable these types of works to be delivered efficiently, with minimal disruption and assured weatherproofing for many years after the installation.

Weathering the storm

A resilient roof relies on durable components and a robust design. Combined, these factors must create a system that is resistant to all types of extreme weather, moderate movement cycles, and any impact on the roof from a falling object. The system should also allow any future maintenance or repair work to be carried out quickly and effectively.

The waterproofing membrane is a crucial component in the system and must provide the attributes needed to ensure resilience. Specifying an EPDM single-ply membrane is a highly-effective solution that will meet these requirements and can be used for flat and low-slope roofs on all types of building.

Made from a synthetic rubber compound, EPDM membranes are highly flexible and can be elongated by more than 300% without any detriment. This allows them to return to their original shape and performance after severe weather and remain stable for decades.

A chemically-inert material, EPDM has a low environmental impact and does not contain any plasticiser. It is also resistant to factors that can accelerate wear and tear over time such as UV, heat, hail and building movements.

If there was a situation that did result in the need for a repair, an EPDM can be easily restored by a contractor using simple procedures and tools. Even after many years of use, the durability of the membrane will avoid the need for a costly strip out and refurbishment. This durability also means the membrane can accommodate rooftop additions, such as solar panels, minimising the potential for any damage during the install.

If solar panels do need to be retrofitted, an EPDM membrane offers a further benefit as it will be resistant to the extra heat that is generated.

Installing a resilient roof

The specified membrane must be installed to the right standards to ensure a resilient roof that performs as expected. All roofs are different so many factors will need to be considered prior to selecting the membrane attachment system.

For an EPDM membrane, a mechanicallyattached system can provide a fast and cost-effective method, especially for steel or wooden decks. It is most suited to large, open roof areas with few penetration details, such as warehouses.

The RubberGard EPDM system, for example, is mechanically attached using a non-penetrating system. QuickSeam Reinforced Mechanical Attachment (RMA) strips are secured to the structural deck. Large panels of the RubberGard EPDM waterproofing membrane will then be bonded to the framework of self-adhesive strips, meaning no fasteners are required to penetrate the waterproofing membrane. The positions of the mechanical attachment strips will be calculated based on the building’s location and height, exposure level, deck type and fastening system to resist wind load.

Another option, depending on the load-bearing capacity of the roof deck and structure, is to loosely lay the EPDM membrane over the substrate and securely hold it in place using approved ballast such as stones or pavers. This will require extra equipment to move the ballast but, overall, can provide another quick installation that can be carried out in all weather conditions. The ballast covering also provides additional mechanical protection of the waterproofing membrane.

The most versatile attachment system is the fully-adhered system, which is suitable for smaller roof areas, unusual roof shapes and more complex penetrations. The EPDM membrane is bonded to the substrate using

TOTAL ROOF SYSTEM

a specially-formulated adhesive. This solution is highly resistant to wind uplift and lightweight, making it suitable for roofs with limited load bearing capacity.

Robust support

The substrate onto which the EPDM membrane is installed must be sufficiently durable for the roof’s life and anticipated functions. If the EPDM membrane is installed over insulation, an insulation material with a high compressive strength should be used to prevent deformation from foot traffic.

The use of rigid PIR (polyisocyanurate) foam insulation is recommended for roofs where maintenance access will be required throughout the roof’s service life. Greater resistance can be achieved using a high-density cover board on top of the insulation package.

High-density cover boards are ideal for a fully-adhered attachment system where the insulation layer is not compatible with the adhesives. Noncombustible gypsum boards provide a highly-durable option and are often required to achieve the higher ratings required on FM-Global projects.

Controlling condensation within the roof system is another important consideration. A suitable air and vapour control layer (AVCL) should be selected based on the temperature and relative humidity within the building, the deck type and attachment method for the insulation and waterproofing layers. Installing a high-performance AVCL between the structural deck and insulation will prevent condensation forming and possible deterioration over time.

Technical advice

When planning a roof project, it is recommended to take a ‘system approach.’ The system should be decided in conjunction with technical advice from the EPDM membrane manufacturer and applied in accordance with their guidelines. Once the system is approved by the technical services team, and executed by the trained licensed contractor, a long-term warranty can be provided for peace of mind.

Benefits for all

Climate change poses many risks for businesses, and public sector organisations are no exception. As the prospect of more unpredictable and severe weather continues, it is essential that buildings are strong enough to cope. As the first line of defence, the roof has a crucial role to play. A robust design and the right roofing system will ensure a resilient structure that delivers benefits for building owners, occupiers and visitors.

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