As the market for drylining and lining systems has developed over recent years, more and more contractors have recognised the potential for movement from purely internal drywall works to the external cladding market. Steve Halcrow takes a look at codes affecting the outside of the building envelope.

Moving into the external cladding makes a lot of sense as there are many transferable skills and many of the principles of the systems are familiar to drywall contractors.

There are, however, also some methods, systems and codes of practice that are unique to the world of façades and insulated cladding. Drywall contractors, particularly those making early forays into that market, should be very careful to ensure they have researched the matter as thoroughly as possible.

An obvious first consideration is system selection and design. There is a wide variety of systems available on the market and many subtle differences between them, and it is vital to ensure all elements of the design have been properly covered e.g. thermal performance, airtightness, wind load capacity, etc. On the face of it this is no different from comparing drywall systems, but the differences can be subtle yet crucial.

Should you begin to delve into the waters of design of these systems it is vital to ensure you have adequate professional indemnity insurance cover (PI), and insurers will be very interested to know your credentials in terms of knowledge and experience in façade systems before covering what is, to them, a far greater risk than forinternal works. Of course most of the manufacturers supplying these systems will have some kind of design support offering, so you can, to some extent, fall back on this, but don’t assume you are covered without checking carefully or a nasty surprise may await you!

Most of the systems available will be tested to either CWCT (Centre for Window and Cladding Technology) standards, and/or have a BBA certificate, depending on the type of system in question. It is imperative to make sure the systems you use are accredited by the appropriate authority and that their use for a particular application has been carefully considered and approved by an appropriately qualified person or body.

If you are working on a scheme covered by NHBC you must be sure you comply with their particular standards – and indeed all NHBC schemes require systems to be covered by BBA certification. Particular documents with which you should become familiar very quickly are NHBC Standards Chapter 6, Curtain Walling and Cladding and Chapter 1.2, A Consistent Approach to Finishes, the latter of which deals with installed tolerances and expected standards of workmanship.

Check carefully that you understand Building Regulations requirements. Parts L and B are probably most pertinent (these cover thermal and fire performance respectively) and, in the case of fire, NHBC once again has some specific requirements with which you must comply.

An example of this is the regulation which requires buildings over 18 metres in height to possess certain fire resistance characteristics. There is a limited number of products and systems on the market that you can use and safely comply.

In addition, NHBC states that there must be vertical cavity closers at centres not exceeding six metres, and additional ones at no more than 1.5 metres from an external corner. This compartmentation is in addition to the Building Regulations requirements, to control the spread of smoke and fire. From my dealings with members’ technical issues I can see that this is an issue that has been overlooked or misunderstood with costly consequences, so make sure you know your standards!

As ever, the message is read your contract carefully. In there you will see that there are specific standards to be adhered to, that certain levels of design responsibility may be apportioned, and it is the place where all the risks lurk. It is up to you to find them and deal with them, or else what started life as a great business opportunity and a chance to diversify, could become a nightmare. If in doubt, ask; we are here to help and support you.

Useful links

British Board of Agrément
Centre for Window and Cladding Technology
National House Building Council