Roofshield & BS5534
In 2015, the latest version of the BS5534 Code of Practice for Slating and Tiling will be one of the hottest topics in the construction industry. After several years of discussion, this new document introduces significant changes to the design, specification and installation of roofcoverings and underlays. The A. Proctor Group contributed to the development of this standard and as such have fully compliant specifications available immediately.
Based on fully independent 3rd party testing, Roofshield can continue to be used across the UK. This, in addition to no requirement for high level ventilation or the use of a vapour control layer, ensures Roofshield remains the simplest and most cost effective method of achieving regulation compliance.
By continually improving our product ranges to reflect the changing criteria and scope of these standards, the A. Proctor Group aim to make these transitions as painless as possible for our customers.
Our Technical Department are available to handle any BS5534 questions you might have, call us on 01250 872 261.
Roofshield BS5534 Zone Guide
Why does Roofshield perform so much better than the competition? Roofshield is an air permeable breather membrane, and also has the highest vapour permeability of any roofing breather membrane. The NHBC have officially recognised this categorical difference between breathable roofing membranes by allowing Roofshield to be used without any low or high level ventilation on NHBC compliant projects. To find out more about the difference between air permeable & airtight breather membranes, read our full article.
BS5534 - Changes and The Implications To The Industry
Twenty years ago the UKs top performing vapour permeable underlay, Roofshield, was not even launched. In those days we were working under the Code of Practice BS 5534 1990 Part 1(25 pages - now 173 pages) and if you were looking for a roofing underlay you had the choice of traditional bitumen felt, single layer non-woven polypropylene membranes, Flash spunbond or reinforced polyethylene’s with micro perforations.
The only vapour permeability requirements were in fully supported applications like boarding and required to have a vapour permeability of 36g/m2/day in accordance with BS3177. For underlays not fully supported the recommendations were to use BS747 bitumen felt and if using a polyethylene film of 0.13mm the batten gauge should not exceed 100mm.
Fast forward to 2015 and vapour permeable membranes are now used on most projects in the UK. Over this time, vapour permeable underlays (now typically with MVTRs greater than 1000g/m2/day) have allowed ventilation requirements for roofs to be reduced to ridge-only, or in the case of a high performance air permeable membrane such as Roofshield, eliminated altogether.
Alongside this evolution in the roofing technology, the climatic factors affecting roof design have also changed, with extreme weather conditions occurring more frequently than in the past. The increasing likelihood of violent storms conditions across the UK has demanded a more rigorous approach to roof design, amid a growing recognition that the old principles are no longer fit for purpose.
The recently published BS5534 effective from the end of February 2015 reflects this new reality with far reaching and more rigorous design standards for both the fixing of roof coverings and the robustness of underlays of all types.
Under the new standard, traditional methods such as mortar bedding of ridges and hips can no longer be relied upon to resist wind loadings, therefore designers and roofers will need to familiarise themselves with the new requirements, and seek updated fixing schedules from tile and slate suppliers.
Wind zones 1 and 2 comprise the majority of England and Wales, wind zone 3 the Border areas and major population centres in Scotland and Northern Ireland, with the Highlands and Islands making up wind zones 4 and 5. Underlay manufacturers must now clearly state in which zones their underlays are suitable, and if any special installation conditions apply in a given zone. These specifics may include, for example, taping of lap joints, variations in batten gauge or reduced batten spacing in higher wind load zones.
The new changes to BS 5534 should be embraced by the industry and recognised as a raising of standards and producing less problems on roofs due to wind damage.
Based on fully independent 3rd party testing, Roofshield will continue to demonstrate its performance by being compliant throughout the whole of the UK.
For zones 1-3, no special measures are required for open rafter and fully supported applications, beyond ensuring laps are extended (if necessary) to coincide with slate or tile battens. For zones 4 and 5, designers and roofers should consult the A Proctor Group to review the specific application, however for the majority of fully supported applications (such as onto timber sarking, commonplace in these geographic areas) no special measures will be required. If special measures are required, a detailed specification will be issued giving the options for compliant installation.
While significant changes to the long established standard are a source of some upheaval and understandable concern to the construction industry, embracing these changes can only lead to the raising of standards, reducing the likelihood of subsequent problems and expensive remediation.
By continually improving our product ranges to reflect the changing criteria and scope of these standards, the A. Proctor Group aim to make the transition as painless as possible for our customers.
Roofshield & BS5534 FAQs