Another option available to Dutch housebuilders is to have concrete walls precast in the factory, cast the brick outer leaf into the concrete, sandwich the insulation between, and fit the doors and windows as part of the process. Combine the wall panels with precast concrete floors and a timber panelised roof and you have transferred building of the whole house shell to the factory and reduced the site build to a process that takes little more time than putting up a tent. “After the foundations are in we start assembly at 7 am and by 5 pm the roof is on and we can lock the front door of the house and go home,” says Harry Van Rosmalen, sales director of Dutch concrete wall panel manufacturer Sterk.
Such brick-faced concrete panels are currently used for only a tiny fraction of new homes in the Netherlands, but interest from Dutch housebuilders is growing, for reasons that are striking a chord with UK practitioners. “The big advantage is that you know exactly what you will get and when you will get it,” says Van Rosmalen. Dutch tunnelform construction may industrialise the housebuilding process, but it is still a site-based operation, subject to the vagaries of the weather, and it still ultimately requires site skills.
For social housing providers in the UK, the Dutch panel system merits exploration as a way of raising productivity and complying with the requirements of such standard-raisers as Sir John Egan’s construction taskforce and the Housing Forum. Rhys Owen Chartered Architects is one of the few UK firms to have already taken an in-depth look at the Sterk system’s potential here, for a 25-unit social housing scheme intended to be one of the Housing Forum’s demonstration projects. “The project called for us to design a scheme that could be built using a number of different systems,” says Rhys Owen. “We looked at steel frame, conventional brick and block, timber, concrete and volumetric - Sterk panels were one of the systems we considered.”
In the event, the project team opted not to use Sterk panels for this project. “They would have been great - had they been manufactured over here. The issue was transport costs from the Netherlands to the UK. They were too expensive, but only just,” says Owen.
Concrete panels are available from UK manufacturers, but faced with thin brick slips rather than whole-depth bricks. The Dutch alternative has advantages, claims Van Rosmalen: “Our panels give the same aesthetics as a brick wall, and because we are using whole bricks we can use any products that the architect wants and create any patterns.”
Sterk’s manufacturing process is similar to that for brick slip-faced concrete panels. Bricks are simply laid in the mould, with a standard mortar around them to form what is in effect a horizontal brick wall. Insulation is laid on top, and wall ties put in position. The concrete is then poured to form the final element of the cavity wall.
The concrete is made with Lytag lightweight aggregate because, explains Van Rosmalen, “the concrete is 20% lighter than normal concrete, the insulation value is a little better, and walls breathe more, so there is less risk of condensation.”
Sterk’s system also allows panels to be recycled. “ We can take houses apart and erect them elsewhere,” says Van Rosmalen.
It is nonetheless a surprise to find the Dutch covering up concrete with traditional brick. Isn’t the Netherlands the home of progressive architecture and even more progressive housebuyers? “Twenty years ago we thought our kids wouldn’t be using bricks by now,” says Van Rosmalen. “But people still love brick houses.” With that sentiment so deeply entrenched in UK housebuilders’ and housebuyers’ minds, a home manufacturer might find a ready market here.
Source
Building Homes
