British Standards are a dry topic, not often the focus at dinner parties.  However, the key Codes of Practice are of great importance to an industry, and this particular one is the basic reference for all flat roofs. It may not be the law, but it is a practical summary of Good / Best Practice for our industry.

As the industry progresses and time marches on, new products and systems appear and are embraced by contractors and designers alike. Older, traditional methods continue, but even they may have innovative changes. At the last revision period in 2001-2003, liquid systems were a small sector, torch-ons were the rage, CDM was little known by many and PU (polyurethane) adhesives were still very new!

Today, many roofing contractors only use PU adhesives, never fire up a bitumen pot and more and more frequently advise their clients on the best-performing and most durable flat roof systems. 

Over the last 18 months or so, the British Standard Committee responsible for flat roofing standards, B/546, has been quietly working away at bringing our Code up to date.  After 12 years of elapsed time, this is not a mere exercise, but has evolved into a major re-write.

The old reference reaches 37 pages, and as BSI charge by the page it was quite expensive.  As a result, many of those who should have referred to it did not purchase and the principles were therefore not well-known or followed.

This time, the members of B/546 were clear that it should be a leaner and more user-friendly Code that would have the following major advantages:

  1. More readable and hence more useful to a wide spread of readers
  2. Simpler language where possible to improve a) above
  3. More compact – and hence more useful
  4. More compact – and hence less costly!

All of these factors are intended to get this new version more widely used, which will improve the quality of flat roofing and therefore its perceived value, leading to more business for all.

A key decision has been to focus the new Code on flexible membrane systems alone. This may sound strange, but the last issue and its predecessor both included guidance on all types of sheet metal roofing, which led to numerous areas of possible conflict in the text, e.g. the separation and ventilation beneath a lead or zinc roof needs to be included and adequate, whereas in a membrane roof, voids are to be avoided at all costs! We have asked British Standards to approach the various metal roofing associations to discuss a separate metal roofing Code of Practice.

BS 6229:2015 will therefore include the wide range of available membrane systems; Reinforced Bitumen Membranes (RBMs), single-ply membranes, mastic asphalt, liquid waterproofing systems, hot-melt bitumen systems, etc., but will not cover lead, zinc, copper, etc.

 Many areas have been covered in debate, including drainage falls, insulation advice, types of roof design, etc.  I can disclose that the Warm-decked Roof is now officially the preferred option, whether it is a pure Warm build-up or an Inverted Warm style.

This finally acknowledges that the Cold-decked roof has had a history of concerns and issues with condensation, which have worsened as insulation requirements have been ramped up in successive issues of Part L of the Building regulations, and that it should be very carefully considered and designed.    

Drainage has been a source of lengthy debate/ dispute, based on a disappointing number of roofs designed at zero falls, but which actually presented the roofing contractor with a series of RWOs with negative falls, i.e. a series of large ponds to waterproof effectively.  In many cases, the extruded polystyrene (XPS) insulation will spend its entire life underwater, which is not optimum.  The new Code will require the designer and main contractor to provide a suitable FLAT surface for our people to waterproof and insulate.

In case there is any uncertainty, the recommendation for membrane roofing is to design in a good deal of drainage fall, towards RWOs that are located (ideally) at mid-span where the maximum roof deflection is. All too often, the RWOs are bolted alongside the strongest location (a structural column), which very often becomes the highest point on the roof surface; hence the outlets cannot drain effectively.  To achieve the desired required finished fall, one should design to double that figure, i.e. for a finished 1:80, design at 1:40.

The new leaner Code will present the information in a new and more logical and rational sequence; the current draft includes:

  • Scope
  • Terms and Definitions
  • Design
  • Materials
  • Workmanship
  • Care and Maintenance

These are followed by the Normative references – British Standards referred to or applicable to the field – and then other publications with relevance to our industry, such as BRE Digests, Trade Association guidance, etc.  

Readers should be aware that this is not a Regulatory document; the Foreword states:

As a Code of Practice, this British Standard takes the form of guidance and recommendations.

It should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading.”    

Having been involved in the 2003 revision and now this one, I am certain that the 2015 Code of Practice will be a far more usable and useful reference, which ought to be very popular with Specifiers of all types, Roofing Contractors, Main Contractors and even Building Control Officers. 

Paul Franklin

Mr. Paul Franklin,
Technical Manager at RAM Consultancy (NFRC Supplier Member)