Housebuilding is undergoing a quiet revolution

As a country we are obsessed with houses: designs, locations, interiors and, most of all, values. Yet, curiously, there’s one vital factor that’s almost universally ignored. Developers don’t mention it in their glossy brochures. Estate agents rarely refer to it. I mean, of course, construction – the way we build our homes.

Bricks and mortar is perhaps the nearest we get before we take up self build, after which we know we’re actually talking about brick and block. This is the way most British homes are built and is, in principle, the way we have built for hundreds of years – that is, by hand, with materials delivered on site, using tradespeople who are predominantly self-employed.

Just don’t count on things staying that way. It’s not that change will be dramatic or instant. Chances are most houses will continue to look just as they do today, ie predominantly brick clad. It’s underneath where it will happen. And is happening as I write.

Housebuilding is, in reality, going through its biggest crisis in over a century. There are multiple reasons why – from an accelerating shortage of skilled tradespeople to the increasing difficulties that traditional construction has in meeting ever more stringent energy-efficiency regulations. Basically the old methods are creaking, both in terms of the quantity of housing they can provide, and the quality.

Even the government admits there’s a problem in its Fixing The Broken Housing Market report published this year.

But the good news is that housebuilding – a notoriously conservative industry – is being forced to look at alternative approaches. Approaches that are well established abroad but relatively little known here. And almost all promise faster, more energy-efficient and more reliable builds.

So what are they? The great majority involve some degree of modular construction, where parts of the structure are produced in a factory under controlled conditions. This shortens the build time, reduces the impact of weather and ensures much greater precision in the way houses are put together.

Best known in the UK is the so-called open-panel timber-frame system. The prefabricated frames are braced with OSB to create rigid boxes which are assembled on a prepared foundation. Insulation is then fitted inside and vapour barriers installed on interior and exterior surfaces.

Closed-panel systems complete these processes in the factory. They are more common in Europe where manufacturers like Hanse Haus and Baufritz prefabricate whole walls, complete with windows and doors, wiring and plumbing. This makes it possible to erect a house shell on a prepared site in just one day. Timber frame’s key advantages over masonry are that it’s both more inherently thermally efficient and hollow. Insulation can be fitted inside the frame, reducing the overall width of the wall. It’s also a dry system, eliminating the need for a lengthy drying out period after completion.

SIPs

One ingenious system, developed in America, both maximises the insulation potential of timber frame and greatly enhances its strength. Structural insulation panels or SIPs consist of two sheets of engineered wood – usually OSB – sandwiching a rigid insulation core. This makes them up to six times stronger than a standard timber frame.

When SIPs are erected, the insulation in each panel directly abuts the next, creating a continuous airtight seal – so airtight, in fact, that mechanical ventilation systems are normally specified. SIPs are one of the most effective ways of creating an ultra-energy-efficient home with relatively slim walls.

Newer to Britain is cross-laminated timber (CLT). Built from solid engineered wood laminated in three dimensions, it’s as strong as steel but much lighter. Whole buildings can be precisely prefabricated and assembled swiftly on site. Insulation still needs to be applied externally, but the ambience and atmosphere of all-wood homes is said to be unique.

But what if you want the energy efficiency and accuracy of a prefabricated home plus the solidity of traditional brick and block? Luckily, there are methods of building with masonry that can easily match the advantages of prefabrication.

The best established is insulated concrete formwork (ICF). As with SIPs, insulation and structural support are combined, but using poured concrete instead of timber. Walls are built from hollow polystyrene forms, either in the form of pre-formed blocks or larger panels, which are put together on site.

Both are designed to lock together, Lego-style. Once a storey is completed, concrete is poured into the forms, which remain in place, creating walls that are airtight and exceptionally well insulated, both thermally and acoustically. Unlike timber frames, ICF can easily create curves or other irregular shapes and can also form basements.

Durosil is a similar kind of interlocking hollow-block system with integral insulation. The main difference is that the blocks are made from a curious mixture of cement dust and wood waste, combining the strength of concrete with the thermal efficiency and ease of working of timber. The inner half of each block contains insulation; the outer is where concrete is poured. Like polystyrene ICF systems, they are capable of being assembled on a DIY basis.

Meanwhile, another system, much closer to brick, is honeycomb clay blockwork, a favourite in mainland Europe. The blocks interlock horizontally and are joined with a thin, glue-like mortar applied by machine, requiring minimal skill. It’s a fast, virtually dry system and the blocks can be filled with insulation for maximum energy efficiency.

So what’s the downside with all these systems? In a word, higher cost, at least on paper. But I’d argue that we’re on the cusp of a change in consumer expectation.

It involves houses that are highly customisable but can still be largely prefabricated, their quality pre-tested and guaranteed before delivery, their erection on site lasting a few weeks rather than several months, their internal comfort similarly guaranteed, alongside fuel bills that barely reach three figures.

Too expensive to achieve? Not worth the extra fuss? That’s exactly what was once said about central heating and double glazing.

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