Overview of changes to BS 5534
Not only will pitched roof specifications now quote BS 5534:2014 + A2:2018, they will also refer to a brand new standard. BS 8216:2018 covers the specification of dry fix products and 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, and better pitched roofing for the UK’s building stock.
Why have new standards been created?
The widespread adoption of dry fix pitched roof systems was driven by the heavily revised BS 5534 that became compulsory in 2015. The choice of products expanded as roof tile manufacturers looked to capitalise on the shift away from traditional mortar bedding to mechanical fixing, and contractors enjoyed the promise of ‘faster and easier installation’.
Two main issues have arisen from this expansion of the dry fix market:
- An increased range of products are available, of variable quality, with no defined way to compare them.
- Site work problems, such as confusion over the installation of breathable membranes and underlays over rafters and the appropriate drape.
These issues, combined with learning lessons from the overhaul of BS 5534 in 2015, have led to problems with finished roofs. The most common include verge systems not providing sufficient mechanical restraint, and failing to shed water from the roof verge without staining the gable wall.
The amended BS 5534, including BS 8216, is intended to combat current poor installation of dry fix pitched roof products, and increase confidence that building owners are being provided with durable, weathertight roofs, both new and refurbished.
What are the changes to BS 5534?
The scope has been updated to include “normal re-roofing work, including repairs".
There is also clarification on the scope in relation to heritage roofs, aware that its recommendations may not be appropriate. Fixing methods for traditional roofing materials often conflict with BS 5534, and consultation with local planning authorities and/or conservation experts is advised, so a suitable approach can be agreed.
As well as referring to the new BS 8216 - covering the specification of dry-fixed ridge, hip and verge systems for slating and tiling - there is support for BS 8000-6:2013, covering workmanship of slating and tiling on site.
Further guidance is provided about roof underlays, including the classification of their wind uplift resistance by prescribed test methods; changes to the definitions of low water resistance (LR) and air permeable underlays; and a maximum drape of 15mm.
Also in relation to underlays, BS 5534 now includes a revised clause about temporary weather protection, before the installation of the primary roof covering, aimed at protecting them from exposure to UV light.
The interpretation of test results determining the wind uplift resistance of roof tile clips has been improved, and there are new definitions relating to the continuity of ceilings.
Ventilation of pitched roofsAnother aim of BS 8216, and therefore BS 5534, is for dry fix roofing to achieve the required level of ventilation while being securely fixed.
Generally speaking, the specification of ‘breathable’ underlays and pitched roof ventilation in combination is not what it could be. The extent to which the ceiling below is made airtight, and therefore how much moisture can reach the roof space, should also influence the choice of underlay and the provision of ventilation.
Marley have manufactured dry fix pitched roofing products for 30 years. They offer a range of roofing systems, products and accessories backed by a full 15-year system guarantee. For answers to any questions about the implications of the new standards, contact our technical team on 01283 722588, or find your local Marley specialist here.