Getting the numbers to stack up when you adopt an off-site solution is a tricky task. Colin Mitchell of Osborne proposes a few routes to success.

Lauded as the future of housebuilding and the means to address the UK’s homes shortage, off-site manufacture has a lot to live up to. There is no doubt in my mind that under the right circumstances, it is the best way to build quality, affordable homes to the fastest possible timescale.

The problem is that off-site manufacture is a “volume” solution, and its viability is dependent upon large-scale adoption. Getting the numbers to stack up when approvals, cost, time and the Code for Sustainable Homes are all against you is currently a tricky task at best. As with all new approaches or any new innovation, the problem is not necessarily the innovation itself, but finding the best way for it to fit with the existing regime, while ensuring its benefits are fully exploited.

When using a volumetric solution – by which I mean a unit that is factory-completed and transported to site – the issue of approvals is the single biggest problem to overcome. Getting designs through Building Regulations and approved for construction by the Council of Mortgage Lenders takes time. It is also particularly difficult to get units approved when they

are designed to achieve either Code for Sustainable Homes level five or six and have that additional capability built in. Approvals exist, after all, to guarantee durability, not sustainability. Energy efficiency is not assessed at this stage, rather, it is rated on the basis of the finished product.

To be able to meet these approvals and come up with designs that are energy efficient, a large investment in research and development is required. At Osborne we have set up a panellised system, which is developed through our own manufacturer, Innovare. By doing this, we have also managed to integrate our supply chain and can accurately monitor a product’s carbon footprint.

Keeping costs under control is fundamental when using a volumetric system. Volumetrics are prone to incurring “profit on profit” because they comprise several components packaged together, each with its own profit built in.

There are two ways to recoup these costs: go into the manufacturing business yourself and “unpick” the package, as we have done with Innovare; or offset the costs through time savings. Speed of construction is, after all, off-site’s biggest advantage. For example, by using a closed panel system we can build a watertight unit within a day and a half, with all the obvious advantages for the rest of the build programme that this brings.

However, all too often, in the following 16 weeks, time savings are simply thrown away as the build progresses. The head start goes to waste because follow-on trades are not programmed in sufficiently early. With the biggest advantage of the volumetric system squandered, there is no chance of recovering the additional costs.

Volumetric systems do not work in isolation. They require complementary programming systems, R&D, a well-controlled supply chain and approvals system

To avoid this, a whole new way of working needs to be implemented with a focus on “lean programming”. This can be achieved by using a critical-path programming method that provides the certainty required to ensure everyone knows when individual tasks will start and finish.

The system used at Osborne works on a traffic light basis, so you can see at a glance what’s going on. As long as you are some distance away from your buffer zone, you will only see green and amber, but if you are eating into your buffer time, your reports will show a red light. Using this type of programming method means that site managers don’t have to carry everything in their heads. Supervision and communication also become clearer and easier, and mistakes can be eliminated.

Osborne used this programming method on its Squirrel Close social housing project in Crawley, West Sussex. The system enabled eight weeks of a 46-week programme to be recouped. For workers on site, it meant everyone had a clear picture of what was happening and when.

On other, more complex projects, we used a “white board” system. This shows the tasks that are to be started on each floor and in each area in any given week. Each task is colour coded to indicate how critical it is, and the system provides the entire site with information that previously may only have percolated as far down the chain as a general foreman. For the client, it not only ensures a speedy build but, crucially, gives it certainty on the handover date and clarity of progress in the weeks before the handover.

Despite the complications, the potential for off-site construction remains enormous.

Not only because it is fast, but also because it can be designed to be very sustainable. However, volumetric systems do not work in isolation. They require complementary programming systems, continuing R&D, a well-controlled supply chain and an approvals system that can accommodate and encourage, rather than hamper, the innovation that we all hope to see continue.