Changes to BS 5534: What specifiers need to know
As a code of practice, British Standard (BS) 5534 provides recommendations on the slating and tiling of new and repaired pitched roofs, and vertical cladding.
Prior to 2015, specifiers might not have given much thought to the application of its guidance. For many projects, the roofing contractor would be responsible for the installation and fixing of the selected roof covering.
A system approach to pitched roofs
Significant revisions to BS 5534 in early 2015 started to change that. For a roof to meet the standards of practice required, mortar could no longer be relied upon as the only means of securing the roof covering.
Single lap roof tiles, and hip and ridge tiles, all had to be mechanically fixed regardless of the use of mortar; tiles to the perimeter of a roof had to be fixed twice. The new version of the standard assumed higher wind loads, requiring more fixings generally.
This drove up demand for ‘dry fix’ systems - products from roof tile manufacturers requiring no mortar, and which are mechanically fixed only. Dry fix systems already existed - Marley have been manufacturing them for 30 years - but the emphasis on them spurred product development and brought new manufacturers to the market.
The role of the specifier increased as a result, needing a more holistic approach to pitched roofs. BS 5534’s new requirements meant selecting products and systems that not only achieved the right aesthetics, but also the quality of installation and the required level of ventilation - all with the appeal of a potentially maintenance-free roof.
Standards in 2018: BS 5534 and BS 8216
A second amendment to the ‘new’ BS 5534, introduced in early 2018, takes things a step further to improve the quality of dry fix system design and installation.
It refers to BS 8216, an entirely new standard and the first of its kind, covering the specification of dry-fixed ridge, hip and verge systems for slating and tiling. It has been some three years in preparation, and aims to ensure that roofs achieve the security, durability and weather tightness expected of them.
It gives minimum performance standards for manufacturers to meet with their products, such as making sure the materials they are made from meet certain expectations. Given the range of dry fix systems that have become available in recent years, for specifiers that means selecting products and systems that have been tested to meet the criteria of the new standard.
It also means making sure pitched roof specification clauses are up to date in project documentation. Even more so than in the last three years, specifiers have a leadership role to play in setting out expectations for product and installation quality, and making sure that level of quality is maintained right through to installation and the finished building.
Conservation and heritage pitched roofs
Specifiers working on conservation and heritage projects, where product selection can be much more involved and detailed, will be used to finding that fixing methods for traditional roofing materials often conflict with BS 5534.
The new amendment clarifies the standard’s scope in relation to heritage roofs, aware that its recommendations may not be appropriate. Consultation with local planning authorities and/or conservation experts is advised, so a suitable approach can be agreed.
BS 5534 and BS 8216 in summary
It’s not just product testing and quality covered by the new and revised standards. The system approach to pitched roofs is further emphasised with advice on the testing and installation (including drape) of breathable membranes and underlays, and on the communication of ventilation requirements for roofs.
BS 8216 has been written to support better implementation of BS 5534. The two are closely linked, and should result in specifications that are easier to achieve in practice. Roof tile manufacturers, like Marley, are already adapting to the new requirements and introducing new products that support the aims of both documents.
There is a transitional period, and external testing bodies are not ready to undertake the full range of product assessment. For now many declarations - particularly dimensional requirements - will come from manufacturers themselves. It’s therefore important to be confident working with an experienced roof tile manufacturer who can explain how and why their products meet the new criteria, and help you generate a system specification.