A roof access walkway is a complex and technically demanding specification which involves a range of important considerations relating to performance, safety, installation and its compatibility with the roofing structure. Here are 10 tips which cover the key factors which determine a suitable design and installation…
1 Choose lightweight material
The weight of an access walkway is an important factor as roof structures can be fragile substrates with a limited loadbearing capacity in comparison to other floors of a building. Therefore the material used for an access walkway must be relatively lightweight, but sufficiently robust to bear the load of light pedestrian traffic. With a high strength-to-weight-ratio, aluminium is an excellent material in this respect: it is one third of the weight of steel yet strong in construction.
2 Check the loadbearing capacity
A roof walkway system should meet the load bearing requirements contained in BS EN 516:2006 Prefabricated accessories for roofing-Installations for roof access-walkways, treads and steps. This states that the walkway should be tested with a load of 1.5Kn over an area 100mm sq and deflection kept within 15mm or 1/100 of the span whichever is the lesser. The load is then to be increased to 2.6Kn and held for a minute. For other specifications consult requirements contained in BS EN 1991-1:2002.
3 Make sure the walkway provides a safe surface
To maximise safety is vital that a walkway surface is designed with anti-slip qualities. There are a number of ways to achieve this, such as a ribbed surface, serrated surface or a combination of both. Timber is an unsuitable material as surface water makes it slippery underfoot.
4 Make sure the walkway is free-draining
Pooling of water is potentially hazardous on any pedestrian area and especially so on a roof structure which is exposed to the elements. A walkway must have sufficient built-in drainage to prevent pooling – this can be achieved with a combination of cross-bars and longitudinal bearers which provides a suitable foot contact area without compromising drainage capability.
5 Incorporate a suitable guardrail/handrail where required
If the roofing structure is a fragile substrate, care must be taken to provide adequate protection, especially near a valley or parapet. Walkways can be used in conjunction with a suitable mansafe system or handrail that can be incorporated as part of the walkway to provide additional safety. For guidance consult BS EN 1991-1-1:2002 as the loading is dependent upon the protection required from the min 0.22 Kn/m for walkways not more than 600mm wide.
6 Check the installation requirements
Another worthwhile consideration for a walkway system is the speed and ease of installation it provides. If the fixing method is complex and requires multiple tasks, this can create unnecessary time and cost spent on site. Avoid any systems which require hot works (e.g. welding) for the assembly of the components or their installation to the roofing. A walkway should provide a fixing system that can be easily installed by a roofing or maintenance contractor. Some manufacturers provide their own team of installers.
7 Check that the fixing system avoids damage to the roof membrane
Care must be taken to ensure that a walkway can be fitted to a roof structure without compromising its waterproof membrane. Ideally a walkway should enable clamping to the roof profile without piercing the sheeting, but if not the fixing system should be designed to provide secure fixing with minimal penetration. This applies to both the walkway and any associated handrails – some systems provide handrails attached as an integral element of the walkway, thereby avoiding penetration of the roof sheet.
8 Check the system’s suitability in relation to the roof pitch
On pitched roofing structures it is important to check the suitability of the walkway for the specific gradient of the installation. Some systems will be unsuitable for pitched installation whereas some high-performance systems have the ability to be placed on gradients of up to 10 degrees. Consult the manufacturer to ensure that the system has been properly tested to meet the pitch capabilities of your particular installation.
9 Ensure the walkway requires minimal maintenance
When providing an access walkway for roof maintenance, it makes sense to ensure that the walkway itself will not require much maintenance. To minimise ongoing maintenance, the materials used should be corrosion resistant and non-combustible. Aluminium provides both of these qualities – it forms a protective oxide coating which is corrosion resistant and can be further enhanced with surface treatments such as anodizing. A system should be assembled from modular components which are easy to remove and replace individually without dismantling other parts of the structure.
10 Make sure the supplier has specific expertise
Designing a roof access walkway requires specialist knowledge regarding the particular technical demands. Make sure your manufacturer and supplier has the necessary expertise in this area to provide reliable advice and technical support, design consultation through to final installation.