We have recently had a couple of queries about materials blacklists, which we had thought were a thing of the past. Clearly this is not the case, so John Gelder, Content development manager, revisits the issue.
Global bans
In general, global bans and mandates (e.g. "Do not use PVC" and "Use FSC certified timber throughout") should be avoided on principle. They are typically located up-front, e.g. in the Preliminaries, or as an attachment to the contract. This approach may satisfy the client, but has some serious disadvantages, including the following:
- They may be contradicted by detailed text in the project specification (in which products containing some PVC, or timber species not covered by FSC schemes, are specified).
- They could be overlooked if not located with, in this case, all text dealing directly with plastics or timber products, which will be scattered all through the specification. Indeed, putting them into the Preliminaries almost guarantees that subcontractors and suppliers won't see them.
- They are too simplistic. For example, many products (e.g. white goods and electrical items) contain PVC components, and second-hand timber isn't FSC certified so couldn't be used.
- They are unfair – materials and components should be judged on their merits and so a given material such as PVC or a non-certified timber may be specified in one work section where it is the best (in terms of cost, function, availability, health, environmental impact etc.) alternative, but not in another work section where there are better alternatives.
- Such lists are unnecessarily restrictive for designers, and may unduly limit choice and hence limit competitive responses by tenderers.
- They can lead to undue expense if strictly enforced, e.g. PVC-free electrical cables are available, but are much more expensive than PVC cables and so rarely used for ordinary cabling.
- They undermine the rationale behind the specification, which is about giving specific requirements, product-by- product, in the appropriate place – hence the dictum "Say it once
and in the right place". - They are very difficult to enforce, by either the contractor or the contract administrator.
This list demonstrates some of the particular problems such lists create. Currency is one – the aggregate BSs cited were not current when this list was published. BS 882 was superseded by BS EN 12620:2002, and BS 8110-1:1985 (not BS 8110) by BS 8110-1:1997. Interestingly, this is a problem in the BCO/BPF publication too!
Redundancy is another – asbestos is barred by legislation (Asbestos (Prohibitions) Regulations 1992), as is lead for potable water supplies (e.g. Model Water Supply Byelaws 1986), and use of UFF is controlled (E&W Building Regulations Approved Document D).
The list is incomplete – there are many other problematic materials in use in the construction industry. Some of them pose health risks somewhere in the product life-cycle (e.g. high-VOC paints, high-gloss floor tiles, cement, chrome plate, sandstone, lead in paint, heavy concrete blocks, fragile roofs). Some pose environmental risks (e.g. SF6 in HV switchgear, certain mahoganies and ramin, CFCs, CCA preservative treatment, organochlorine pesticides, peat). Some can lead to problems if not properly designed and installed (e.g. acrylic membranes in showers, high-level window glass). Indeed, "all materials have the potential to create risks", as noted in the BCO/BPF publication.
Of course many of these materials are covered by legislation (e.g. EU Directive 2004/42/CE on VOCs in paint, Montreal Protocol, CITES), which perhaps explains why they are not in the list, but this only raises the further objection that such lists are inconsistent – why mention some controlled materials but not others? In some cases the general legislative ban might not apply, e.g. lead-based paints can be used in certain conservation projects.
For most of the products listed, their inclusion in such a list was not and is not technically justified. A perusal of the BCO/BPF publication will make this clear. Indeed the matter has gone to court a couple of times, e.g. on calcium silicate bricks in UK courts (e.g. Kirkforthar Brick v West Lothian District Council), and on Iberian slates in the European courts.
What to do if you receive a blacklist
If a list of prohibited materials is provided and insisted upon, then architects and others have some choices to make. Generally, review the list, query any inappropriate exclusions, and convert remaining valid exclusions into positive requirements stated at the appropriate point in the specification.
For example, instead of stating "Permanent formwork: Do not use wood wool slabs", state "Permanent formwork: Wood wool slabs to BS EN 13168" (not BS 3809 as in the BCO/BPF publication, but residual content may be an issue).
If the list is a post-contract requirement, e.g. from potential tenant or purchaser, valid exclusions should be converted to positive requirements via architect's (or CA) instructions – any conflict with the contract specification will be easier to spot than if the list itself is passed on.
Conclusion
Outright bans and mandates never made sense. Instead, advice to specifiers on any circumstances in which materials should and shouldn't be used, and on how to use them so that no risk is posed, would have made more sense – hence the BCO/BPF publication. However, calling up this publication in the contract (as in JCT MPF 05) for contractor-design probably isn't sensible:
- Its scope is too limited (what about materials not mentioned therein – anything legal goes?).
- It isn't current (and so may conflict with the specification).
- It is non-enforceable, being written as advice rather than as specification.
Cook (1997) suggested that "... a general clause prohibiting the use of materials not conforming with British Standards and other codes of practice could be included in contracts". This doesn't make much sense, for all the reasons already mentioned, and because there are many new (e.g. straw bales) and not-so-new (e.g. thatch) materials for which there are no British Standards. Plus it stifles innovation (products new to market won't have BSs in place yet) and will lead to conflict, e.g. where German or American proprietary items are used.
The conclusion – rely on a well-written project specification, and ban the ban!
