The offsite manufacture of houses is also known as kit-house construction and pre-fab construction. It’s been a mainstream form of house construction for decades in Germany and other European countries and is now a growing build system in the UK. Off-site manufacturing of self-build houses is essentially the manufacture of pre-insulated wall, floor and roof panels which are then transported to site for rapid assembly.
More and more services and features are being pre-installed at the factory as this improves both productivity and the final quality. So in addition to the door and window apertures being pre-cut, the doors and windows are also pre-installed. Wall and roof cladding can be pre-fixed, likewise internal plasterboard. As required, ducting can be included for plumbing and electrics, sometimes with the services also installed. Key considerations are:
Factory fabrication does not mean standardised design; it’s more likely that the design caters for your individual tase and your lifestyle. However, this requires that you think through all the details at an early stage, ahead of the manufacturing design process. Once the designs have been signed off and passed to the manufacturing unit, this is what will be produced.
2. Quality control
High energy performance needs airtightness that is only achievable through accurate panel fabrication and realisable in factory conditions. Ensuring that the house creates a healthy living environment means installing only the right materials and systems, requiring full control over the supply chain. This extends to specifying the type of insulation, surface finishes, paints, air filtering systems etc.
Minimising construction time required on site means that there is less chance of delays occuring, whether due to weather, late deliveries or the unavailability of personnel. This means a more predictable date for completion of the weathertight house, which allows for more reliable scheduling of the fit-out trades. The end result is a house that is completed more efficiently than traditional methods.
3. Simpler Build Route
As so much of the shell preparation work is done in the factory, the actual assembly on site is relatively straightforward with the services of an experienced assembly crew. With the house weathertight and the trades able to work in the dry for the majority of the time, the fit-out can largely follow your prepared schedule with the minimum of delay and stress.
It is not easy to compare the cost of factory-fabricated houses versus traditional build as there are so many fluctuating factors. Factory-fabricated houses make savings because they require less site-labour but the cost-per-panel is high as the manufacturer seeks to recover fixed costs relating to setting up the factory. Smaller manufacturing units are being set up by entrepreneurs, such as the flying factory (see article), which will produce more competitively-priced panels. However, material costs will undoubtedly rise and keep on rising due to the effect of Brexit on our mostly-imported timber.
What is certain, though, is that you will get terrific value for money. You will obtain a beautiful home designed around your lifestyle, built to last and with impressive energy-saving features.