The crane operator does not look at the building. He watches a man in an orange vest who stands on the fourth floor of a half-dismantled housing slab and talks into a radio, slowly, as if to a horse. The cable tightens. A wall panel the size of a small garage door lifts free of its neighbours with a sound like a drawer opening, and swings out over the yard.
Below, someone has chalked a number on the panel: 4-17-W. Fourth floor, seventeenth bay, west wall. In a few weeks it will be trucked to a field on the edge of the city, checked, cleaned and stacked. In a year, if the plan works, it will be a wall again, in a different building, for different people.
Most slabs like this one simply get knocked down. Housing associations in the Netherlands demolish somewhere between ten and fifteen thousand homes in an ordinary year, many of them in exactly this kind of block.1 The reasons are familiar: the flats are small, the insulation is poor, the lifts stop at every other floor. It is usually cheaper, on paper, to start again.
Built like furniture
What makes reuse possible is the very thing that made these buildings unloved. They were not really built at all. They were assembled. In the 1960s, factories cast walls and floors by the thousand and cranes clicked them together on site like flat-pack furniture. The joints were steel plates and grout. In principle, what was bolted can be unbolted.
In practice it is fiddly, heavy work.2 The grout has to be cut out by hand. Every panel is a little different from its drawings, because the drawings were never quite right. Some connections have rusted; some were never made at all. The team spends its first month on each building just looking.
“You have to read the building before you take it apart,” says the lead engineer, who started this work as a side project and now does little else. “It tells you how it was made. Sometimes it tells you the builders were in a hurry on a Friday.”
Every panel that leaves is tested for strength and for the condition of the steel inside it.3 So far, the team says, more than eight out of ten pass. The rest are crushed for gravel, which is what would have happened to all of them anyway.
“It's not a ruin. It's a warehouse of parts that somebody already paid for.”
The arithmetic of a wall
Cement is made by heating limestone until it gives up its carbon. That chemistry, plus the fuel it takes, is why concrete has such a heavy climate footprint. A panel that is lifted, trucked and reused avoids nearly all of it. The extra work, the crane hours and the testing, adds a little back.
On their first finished project, a row of eight family houses built from the walls of a slab on the other side of town,4 the engineers think they avoided around two-thirds of the emissions a new concrete structure would have caused.5 The houses cost slightly more than standard ones. The developer expects that gap to close as the process becomes routine.
What the rules don't say
The biggest obstacle is not engineering. It is paperwork. Building codes are written for new materials with certificates from a factory. A sixty-year-old wall has no certificate, only a history. Every reused panel needs its own approval, and every inspector has to be persuaded from scratch.
That is beginning to change. Several municipalities now let reused structural elements be approved by test results rather than by a factory label, and a national guideline is in draft. If it passes, a demolition site could become a supplier, and a housing association could sell its old blocks by the panel.
Back in the yard, 4-17-W has been set down on timber blocks next to its neighbours. Someone sprays the edges to wash off the dust. Up close, the surface is smoother than you expect, and slightly warm from the sun. It has spent sixty years as the wall of somebody's living room. It is in no hurry to become gravel.