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Specifier Review
safety on flat roofs

Making rooftops safe and secure

With falls from height still a substantial contributor to construction deaths, it is imperative that equipment on roofs is as safe as possible. Poorly secured cables on flat roofs are a major trip hazard as well as reducing the lifespan and function of the cabling. Sam Birch, Technical Manager at Big Foot Systems, looks at the latest methods for securing cabling on flat roofs.

Are you safe and secure on rooftops? Poorly installed cabling on flat roofs can be a major hazard – for both rooftop workers and for the cabling itself. Trailing cables or badly made and installed cable trays can result in serious trip injuries or falls if near the edge of a roof. According to the Health and Safety Executive (HSE), falls from height are the biggest workplace killer, accounting for 40% of deaths in 2018/19. And in the same time period, 8% of non-fatal injuries were caused by falls from height and 29% were caused by slips, trips or falls on the same level.

Cable tray systems are often used for cable management in commercial projects to support insulated electric cables on flat roofs. Traditionally, cable trays were often supported on concrete paving slabs or attached to trimmed down struts as a simple, speedy, cheap, support solution. But the old ways are not always the best. Concrete slabs and cut down struts are not the most neat and tidy or safe and secure option. In fact, concrete slabs barely raise the cable trays from the flat roof so run the risk of cables sitting in pooled water and they can also be a major trip hazard.

Many contractors will be aware that it is best practice not to lay cable trays directly onto a flat roof of an installation. BEAMA’s ‘Best Practice Guide to Cable Ladder and Cable Tray Systems’ states that cable ladders and trays should be mounted far enough off the roof to allow the cables to exit through the bottom of the cable ladder or tray. However, although this is best practice, on site this is not always followed and traditional methods can still be found on some roofs.

In addition to safety concerns, there is also the issue of single ply membrane roofs which call into question these makeshift cable trays. Traditional cable tray support solutions can cause expensive long-term problems when used on delicate modern flat roofs made from single ply membrane which can be easily damaged. Placing concrete paving slabs or cut down struts directly on a flat roof with a single ply membrane can tear through the membrane, which can lead to destructive roof leaks and costly damage. Using these traditional support methods may also compromise roof integrity causing thermal bridging or potentially affecting roof warranty requirements. Paving slabs can also prevent drainage of water from the roof, causing ponding and issues elsewhere.

As a result, contractors are now looking for alternative methods to secure cables on flat roofs and opting for non-penetrative support systems which offer a neat, tidy and secure solution with greater protection for cabling, improved safety for roof-top workers, and avoid the risk of damage to lightweight modern roofs.

There are many advantages to using modern cable trays with specialist supports. These high quality non-penetrative, freestanding products, such as Big Foot’s Ancillaries support range, offer a flexible, adaptable and robust multi-purpose solution for ancillaries support including duct, pipe and cable tray. Designed to protect lightweight modern roofs, these offer a range of benefits including cost and time-effective installation and improved system aesthetics without penetrating the rooftop. In contrast, cut down struts, if not treated correctly, can corrode very quickly when installed on flat roofs.

Non-penetrative cable tray supports are designed to protect lightweight modern roofs and offer a range of benefits. The cables are kept safe, secure and above roof level so are protected from water pooling, avoiding trip risks as well as preventing cabling being damaged from any footfall on the roof.

Another key issue is to ensure cable trays and their supports are strong enough. BEAMA best practice guidance states that cable ladders, cable trays and their supports should be strong enough to meet both the current and future load requirements of the cable management system as well as any other additional loads applied to the system. In order to select and design the most appropriate cable ladder or cable tray system for an installation, BEAMA stresses the importance of considering the necessary loads needing support and the distance between the supports.

Nowadays there is a wide selection of non-penetrative supports for cable trays so contractors can ensure they select the right support for an individual project. For smaller cable tray installations, support solutions are available, such as Big Foot’s Fix-it Foot, which offer a tidy roof-top support solution. Available in seven sizes, the feet have an aluminium corrosion resistant channel recessed into the top face to allow for easy fixing of services. Made from UV stabilised, durable, recycled rubber, the Fix-it Foot adds stability and is also suitable for pipework and duct. If extra clearance is required the High Bloc fits underneath the Fix-it Foot, allowing the user to increase the clearance height by an additional 120mm.

For heavier cable tray loads there are multi-purpose support solutions for duct, pipework and cable trays in isolation or in combination, such as Big Foot’s Multi Foot. This type of support solution can take more weight that the Fix it Foot so is ideal for larger cable tray installations and is an extremely versatile and cost-effective one-piece support which accepts 41mm strut and is available in two sizes. The foot is made from black UV stabilised, injection moulded, glass filled nylon. The support allows struts to be fixed into the top and can also take threaded rod, allowing flexibility on larger cable tray installations. The Fix it Foot also has a new integrated mat configuration for optimum roof protection.

safety on flat roofs

Meanwhile for large cable tray installations there are non-penetrative support solutions available to suit heavier loads, such as Big Foot’s H Frame, which are a quick, versatile and economical solution for supporting cable trays, pipework, duct, or any combination of these. Offering a versatile application, installers provide their own strut, keeping the duct and pipe installations low-cost and totally flexible by fabricating the strut frameworks on site. Featuring an innovative design, the H Frame Set 305mm is interchangeable with three strut sizes, with one foot fitting all. It is supplied with integrated adhered rubber mats, with foot fleeces recommended for use on PVC membrane roof surfaces to prevent polymer migration and protect single ply membrane roofs. Additionally, angled mats are available for sloped roof applications.

With efforts to improve rooftop safety and the fact that single ply membrane roofs are becoming more common place due to their high thermal performance, non-penetrative supports offer contractors an option to securely manage cables on flat roofs, avoiding trip risks and damage to the roof’s surface. With this trend for modern methods of construction set to continue, single ply membranes will become ever more common with non-penetrative supports becoming a useful and safe solution for contractors.

For further information on all products and services offered by Big Foot Systems email: enquiry@bigfootsupport.com or telephone 01323 844355.

http://www.bigfootsupport.com/