How Fast Can You Build a House?

I have seen many changes and innovations in the 30 years I have worked in construction, and the majority of these involve some element of time saving. On-site glass fitting has been replaced by factory glazing; skilled screeders by pumps; copper plumbing by plastic; hand-built roofs by trussed rafters; and hammers with nail guns. All of these are designed to ‘save time’ and yet the typical length of time it takes to build a complete house hasn’t changed much at all. Even major shifts towards timber frame and other off-site methods doesn’t seem to have had a great effect on overall build times. Most houses still take eight months to complete, and many take a lot longer — especially where there is a high DIY content.

Now why should that be? Partly it may be because the houses we are building have become more complex, and that we are fitting them out with more features, such as ventilation systems, structured cabling and lighting schemes. But this doesn’t really get to the route of the problem, because complex houses can be built quickly. To see how, we need to look at how other countries build, and a good place to start is Germany, which has developed a house - building industry very different to ours. In Germany, self-build is king and around half of all new homes are commissioned by individuals for their own occupation — in the UK the figure is more like 12%. In order to deliver all these bespoke homes, the Germans have a sophisticated manufacturing industry consisting of hundreds of small- to medium-sized firms capable of building new homes within three months.

Now, obviously, the factory build element is a very important part of this process. Move most of the building trades inside a warm, well-lit environment with computeraided design and computer-controlled cutting equipment, and you can significantly reduce the number of hours required to create a house. But there is another aspect of this process which is just as important, and arguably has more to teach us in Britain.

When you place an order with a German factory housebuilder, you are required to decide on all the finishes – the door handles, the light switches, the tiling – before they will even sign a contract with you. It’s referred to as a ‘design freeze’ and, once in place, there can be no going back, no changes of mind. It’s a key element of any manufacturing process: having achieved a final design, all the information is logged into the computers and the build begins. This enables the Germans to compress the length of the project into just a few weeks. The superstructure often takes just 48 hours to erect; the finishing tasks will take around eight weeks to complete from this point.

In Britain, we tend to take a much more leisurely approach to housebuilding. The design process is often seen as a troublesome overhead to be negotiated as quickly and cheaply as possible. Whilst design packages are fairly detailed for the superstructure, the finishes are often left out completely at the initial stages and are covered by contractual niceties such as ‘prime cost sums’ and provisional figures. Kitchens, bathrooms, electrical fittings, floor and wall finishes are usually left to the client to buy in their own time, as and when it suits them. There is nothing wrong with building this way, but it goes a long way towards explaining why it takes so long for us to build a house in Britain.

Interestingly, the number of hours taken to build a house in the German manner is not vastly different to our more loosely organized sites. Factory builds do reduce man-hours, but the main difference in the build duration is down to the number of people working on a project at any one time. In Britain, we average around three people on site during an eight-month build (totalling around 4,000 hours for a typical detached house). In contrast, the Germans will have much larger teams working both in the factory and on site after the superstructure is erected. This is only possible because of the design freeze. Materials are all purchased and in place at the appropriate time, everybody knows what to do and when to do it. The manufacturing process, which demands a design freeze, actually finishes once the superstructure is up, but the German school still carries out the finishing tasks in the same manner, and it is this process as much as anything which shortens the overall build time.

There is a useful lesson here for all would be project managers: every hour spent on planning the job saves four hours sorting out the mess at the end. Even if you are unable to implement your own design freeze at the outset, you should at least develop a route map through the job. It’s not enough just to know what joinery you will be using, you need to know where it’s sourced from, how long it takes to get hold of, and where it will be stored on site. It’s all very well buying 14,000 facing bricks at a great price, but how will they be unloaded and where will they sit on site? Have a plan not only of the house, but also of how it will be built.

FURTHER READING:

• Kit Homes 
• Alternative Construction Methods
• Timber Frame or Blockwork?