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All things being equal, it makes a lot more sense to make a building in a factory than it does on site. Unfortunately, buildings are not especially portable, so it also makes sense to make elements on a production line and assemble them on site later. The problem here is one of flexibility: manufacturers usually create products for a specific building, rather than for buildings in general, so whoever is designing the thing has relatively little choice in what they specify. If it were different, architects would have a vast world of choice, and everyone else would be all the collateral benefits of standardisation, such as improved competition, availability and quality.

To create this world, the Construction Products Association (CPA) and Build Offsite, a group that promotes off-site manufacture, have decided to create a list of generic specifications for a suite of floor cassettes. Clients would be able to choose from floors built to the standards in several sizes, weights, tolerances and materials, such as timber, concrete, steel and composites. Most importantly, the cassettes would all have common fittings so they could be attached to other parts of the prefabricated building. The standard could also cover integrated services, coverings, finishes, dimensional accuracy, spans, dimensions, lifespan, tolerances and loading capacity.

The team of clients, designers and suppliers that will compile the standard will be assembled over the next month and the list of specifications, which will accredited by risk management organisation Lloyd鈥檚 Register, should be ready in the autumn.

Why start here?

The reason for beginning a general standardisation drive with floor cassettes was that several Build Offsite members, such as airport operator BAA and property firm Great Portland Estates, had already begun developing their own floor systems. Build Offsite thought it made sense to develop this work into a standard and approached the CPA to get suppliers involved.

Standardising the floor cassettes could have a range of advantages. John Tebbit, deputy chief executive of the CPA, says:

鈥淏AA could see it increasing the number of people who could supply the floors. And standardisation of design tends to bring costs down eventually because it stops people from having to do things all over again every time.鈥� He thinks standardisation will also increase the market for floor cassettes as well as client confidence and interest in the product. Demand for the components involved in making the floors would also grow, which could create economies of scale.

Having walked through miles of BAA corridors you can see why it would help them to standardise

Chris Gaze, BRE

A simplified, standardised system should also reduce design time and time on site: designers will not have to start from scratch and construction teams will not have to learn how to assemble yet another new system. What is more, the floors will be quicker to lay, and require fewer tradespeople. And as time on site would be cut, safety ought to improve. 鈥淚t all leads to cost saving and improved quality,鈥� says Martyn Wilson, programme leader for Build Offsite.

Peter Caplehorn, technical director of architect Scott Brownrigg, applauds the idea of standardisation. But he also warns that the construction industry is 鈥渋nherently conservative鈥� and clients, insurers and regulators will need to be won over to the standards. He thinks there could be problems with standardising one element at a time: the benefit of prefabricating wall fixings are lost unless wall panels are also standardised, and the performance of a building is defined by how components work together. 鈥淚t would be good to see the standard spread out as soon as possible to look at it from a whole building point of view,鈥� he says.

Chris Gaze, associate director of productivity and innovation at BRE, says the system could make life easier for contractors because they would be able to bid without having to put in extra costs for unknown risks. That said, he thinks designing a good specification will be difficult.

Both he and Chris Payle, director of engineering WSP, which has worked on a number of projects for BAA, say the scheme could be especially useful for elements that need to be repeated and are unobtrusive. 鈥淗aving walked through miles of BAA corridors you can see why it would help them to standardise,鈥� says Gaze. 鈥淵ou wouldn鈥檛 use it for the Olympic aquatics centre but in most buildings there are certain bits that are utilitarian; it doesn鈥檛 mean the overall building is drab but if you can make those sort of corridors standard you can do something clever with the design elsewhere.鈥�

Payle adds that BAA had originally asked him to work on standardising the piers that house its departure lounges. The use of off-the-shelf elements should speed up construction, which is especially useful if the site has operational constraints or security problems. But Payle thinks that oddly shaped sites or those combining a range of uses on different storeys 鈥� for example retail on the ground floor and residential above 鈥� may need more bespoke systems.

Stewart Dalgarno, director of product development at timber-frame specialist Stuart Milne, says companies will want to be sure the product will sell before spending money on changing their manufacturing process to meet the standard. 鈥淓verybody has set up their factories to a construction process that suits them,鈥� he says. 鈥淚t might not be a deal breaker, but further debate will be needed as well as certainty of volumes.鈥�

If the generic floor specification goes to plan, then Build Offsite may move on to other elements of off-site manufactured buildings. 鈥淭he bigger picture behind this is an integrated building,鈥� says Build Offsite鈥檚 Wilson. The group may look at walls, foundations and roofs and standardise the way they connect together and possibly start work on that next year. He laughs: 鈥淚t will be nice and simple 鈥� like Lego.鈥� If the system is half as successful as that factory-produced system, it will have done very well indeed.