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27 Feb
The recently updated British standard will come into full effect this coming Sunday (1st Mar), after the cross-over period from the change in the standard last August.
BS 5534:2014 “Slating and tiling for pitched roofs and vertical cladding. Code of practice” is a full revision of the standard, which is designed to improve the overall security of roofing structure. This includes a number of changes to fixings, battens, underlay and mortar specifications.
Over the past 6 months, there has been a grace period where either the new standard or the 2010 version can be used. As of the 18th February 2015, new roof contracts must be undertaken in accordance with the 2014 update for full compliance.
What is BS 5534?
BS 5534 gives guidance on the best practices for the installation of a slate or tiled roof across the construction industry. The standard contains a wide range of information across various specifications for fixing and providing a quality end product.
Whilst the British Standard is not enforced as a legal requirement, the standard is in place to protect both those in the construction industry and those purchasing the end product. It helps workers by ensuring that they are covered during any possible disputes and ensures that end customers get a quality installation.
Why the Revision?
The two main reasons for the update are:
– An increase in extreme weather, as gale force winds, rain and flooding events are on the rise in the UK.
– Increased similarity to European standards, so that tougher wind uplift calculations are adhered to.
Changes to Fixing
Fixings on roofing has increased, but in most cases of slates and plain tiles are not affected. The most significant change applies to roofing with single-lap tiles, which will now have to be attached with either a clip or nail.
The key points are:
– All single-lap tiles need to be mechanically fixed
– Elements of the roof on the perimeter will require two fixings
– Double tiles, tile-and-a-half or half tiles should be used to avoid the use of small pieces of cut tile
– Bonding or mechanical fixing is required where small tile cuts are found, such as valleys and hips
– Nails should be inserted with a minimum of 15mm penetration into battens
These new fixing specifications will ensure that roof construction is more robust, giving greater longevity and increased resistance to the elements. Due to the foreseen extra amounts of work with mechanical fixing, there was concern about increased installation time, but many fixing systems are available to help speed up this process.
Changes to Mortar Bedding
Previously, using mortar as the sole means of fixing roof tiles was sufficient, but this is no longer the case. Careful consideration should be given when roofing mortar is being mixed, and an additional mechanical fixing must also accompany the bedding.
When tiles are being installed which are not suitable for a mechanical fixing, then they will need to be drilled and fixed. This work is deemed as “out of scope”, meaning that the standard does not cover it, but work undertaken isn’t wrong or insufficient.
The standard includes guidelines on creating an appropriate mortar, stating that the mixture should be either:
– A mix of 1:3 cement to a suitable grade or blend of sand
– A proprietary dry mortar (bagged and specifically designed for roofing)
Mortar work should also be completed in one operation and within two hours for ridges, hips, valleys and verges, with deeper beds being allowed to be pointed up in a separate stage. This means that the method of bedding with one mix and pointing with another should be avoided. In addition to this, if coloured mortar is to be used, it should be coloured throughout rather than plain mortar with a veneer.
Changes to Underlays
With a range of lightweight underlays available and their usage commonplace, new guidelines have been put in place to ensure their correct usage. In contrast to traditional bitumen-coated underlays, lightweight underlays can “balloon” within the roof space if not secured properly, creating a load on the underside of the roof covering.
Underlays should meet the following requirements:
– Provide a continuous under-roof barrier
– Any penetrations should be sealed to stop water ingress in accordance with BS 8000-6
– Where necessary, laps should be covered by a batten and should be adjusted to coincide with the nearest slating or tiling batten.
– A minimum 10mm drape should be provided in between supports to allow for a drainage path for moisture and to prevent excessive deflection under wind load.
There are a range of options available for nail holes through underlays, including batten tapes.
Changes to Battens
The changes means that the grading of battens can no longer be done on site. All battens will have to be checked off site to ensure that they conform to the new standard, and there is no longer the option of a “part-graded” batten.
Batten suppliers will claim to be BS 5534 compliant, but they often lack a reputable third-party accreditation.
– One if the biggest issues is with the under-sizing of battens. The update includes a clear tolerance limit for the depth of battens, allowing for 3mm over, but not being less than 25mm deep.
– Marking must be present on all battens to identify the origin, size, suppliers and conformance with BS 5534.
– The appropriate accompanying paperwork must also be included to show the type and method of preservation treatment
You should ensure that you purchase battens from a reputable manufacturer – this should ideally be one with UKAS accreditation. Graded battens should also go through a series of checks, ensuring that knot-configurations and other issues meet the requirement of the standard. If issues arise, they should be reported to the supplier as soon as possible.
Equipped with this information, you can easily make sure that your roofing installation meets the updated British Standard. If you have any questions of queries, please get in touch with us, and our support team will be able to help you along the way.