Thecheapest way to make strong mortar is to add washing-up liquid. I learned this from my father, with whom I’d fix cracks and repoint brickwork when I was a child. There were home repairs to make, but my parents also did up houses, so there were plenty of jobs to keep us busy. We didn’t own a cement mixer, so we’d blend our mortar by hand in a wheelbarrow. A shovelful of cement powder, some bright orange construction sand, water from a bucket and, finally, a squirt of washing-up liquid. Then I’d set to work with a spade, folding the powders into the liquid until my arms ached. The next day, I’d survey the darker patches of the mended path or driveway, looking for solidified fox or cat prints.

The ingredients of mortar have barely changed in ten thousand years. In De architectura, the earliest surviving architectural treatise, Marcus Vitruvius Pollio suggests pozzolana for the base: volcanic ash from the Campi Flegrei caldera near Pozzuoli. As aggregate, he recommends sand with a low soil content, ‘which crackles when rubbed in the hand’, as well as a clever method for identifying it: ‘Throw some sand on a white garment and then shake it out; if the garment isn’t soiled and no dirt adheres to it, the sand is suitable.’

Romans had their own secret ingredient for concrete: seawater. It reacts with pozzolana and lime to form aluminium tobermorite, whose crystalline structure runs through the mix like a microscopic scaffold, an atomic simulacrum of the steel skeletons used to reinforce concrete from the end of the 19th century. Seawater can also percolate through the pores, so that structures exposed to it grow stronger over time. Jetties and breakwaters, for instance, are reinforced with each thrashing wave, in an inversion of the usual process of erosion. This peculiar chemistry, which was a puzzle until very recently, explains why the piers at Portus Cosanus still stand, and why the Pantheon remains the largest unreinforced concrete dome in the world.

Vitruvius, who wrote extensively on human proportion, would have been pleased to know that the dimensions of modern bricks are designed to suit the span of a human hand. Bricklayers must be able to hold a brick in one hand and a trowel in the other. The hardest and densest bricks come from my birthplace, Accrington, in the north of England. Nori bricks get their name from an accidental inversion of ‘iron’, which was stamped backwards on the ‘frogs’ (the depression in the centre of the brick) of the first batches in 1887, announcing their high iron content. They were thereafter marketed as ‘Iron, whichever way you put it.’ Noris line the foundations of the Empire State Building and Blackpool Tower, and are the rightful namesake of redbrick institutions, having been used to build the first one: Chancellor’s Court at the University of Birmingham. Their strength derives from iron oxide-rich fireclay, sourced from the coal seams around Accrington, which sits above the mineral-rich bed of an Ice Age lake.

Last summer, I found a mound of Nori bricks near the headland in Hartlepool, remnants of a recently demolished shore-side magnesite factory, in which seawater had been put to another use: it was combined with locally-mined dolomite rock to make magnesia. One of the primary uses of magnesia is in the production of the refractory bricks that line kilns for making construction steel. It’s also a constituent of Portland cement. The sea that was once its raw material is now grinding the factory into granular oblivion. The Nori stamps have started to rub off.

Accrington’s once famed brickworks are now in and out of use. Bricks are in high demand, but most are now imported, so that many UK-based clay pits and factories are dormant: not profitable enough to run, too valuable to be left to rot. Hartlepool and Accrington are both on the UK’s top ten list for empty houses; rows of boarded terraces spell abandonment. At the other end of the spectrum, the luxury towers of ‘buy to leave’ flats in London were once described by Boris Johnson as ‘blocks of bullion in the sky’. Across the country, more than 600,000 homes are vacant, while there are at any time around 4500 rough sleepers. By the end of this year there will be two million people on waiting lists for local authority housing, as the pandemic leaves record numbers in rent arrears. The government’s preferred solution to the housing shortage is, as Johnson says, ‘Build, build, build.’ Home-building is at a 33-year high, even as the regulatory failures exposed by the fire at Grenfell Tower grow more concerning by the week.

I often think of the man whose defective fridge sparked the fire at Grenfell Tower. Fridge fires are common, as are those caused by cooking, candles, hair straighteners, cigarettes and heaters. We now know that not only was Grenfell Tower encased in several layers of incendiary materials, but that a series of manufacturers had lied about this, and successive governments had failed to produce a regulatory environment that deterred them from doing so. The aluminium composite cladding on Grenfell Tower was Reynobond PE, manufactured by Arconic, whose polyethylene filling produces noxious fumes when heated. Developers chose it over Reynobond FR, which cost £2 more per panel. ‘FR’ stands for ‘fire resistant’. (A quick calculation puts the saving at about £5000, or £69 for each person exposed to the toxic smoke on the night of the fire.)

But penny-pinching and negligence is only one part of the story. Arconic has admitted to dismissing the flammability of its PE panels, knowing the cheaper price would appeal to developers. And even if the cladding had not metastasised the fire, the insulating panels would probably have done that on their own. The Celotex insulation used in Grenfell Tower had failed its fire safety check. Seemingly unfazed, the company shielded a panel with inflammable material and reran the test. It passed. But that’s like testing a firework in a swimming pool, a fact acknowledged by the employee who scrawled ‘WTF?’ in the margin of the safety report. A smaller proportion of the Grenfell insulation was supplied by Kingspan, which had changed the composition of its insulation but carried over an earlier safety certificate after it was shown that the new kind burned like a ‘raging inferno’.

As many as eleven million people may now be living between combustible walls. Affected flats can’t be mortgaged without fire safety certificates, which leaves homeowners in a triple bind: their home is unsafe, they can’t leave it and they can’t afford to fix it. The government has insisted that buildings be made safe yet is failing to fund remediation work or to prevent house-builders and freeholders from passing this cost – which might exceed £50,000 per flat – onto leaseholders. Under pressure from leaseholders and some parts of the media, the government has now pledged £3.5 billion towards costs that are estimated at £15 billion, but this money is available only to those living in blocks above 18 metres (and comes with the condition that applicants must refrain from speaking to the press). Those living in shorter buildings are supposed to be comforted by the lower probability of dying in the event of a fire, and will instead be offered loans. Many building-owners have already begun the process of retrofitting safety features and billing them to leaseholders. Some will have sophisticated fire alarm systems installed, which isn’t a solution to the problem of life in a tinderbox, but might get you out in time to watch your worldly goods carbonise from a safe distance. In some cases residents must pay the wages of fire wardens, who patrol the building day and night.

In ancient Rome, the vigiles, a group of state-owned slaves, acted as nocturnal fire-watchers, patrolling the city to spot and extinguish fires, which were common. Despite the stone, marble and concrete, Rome depended on its own combustible composite: wattle and daub. Vitruvius warned of the dangers:

As for craticii, I could wish that it had never been invented. The more it saves in time and gains in space, the greater and the more general is the disaster that it may cause; for it is made to catch fire, like torches. It seems better, therefore, to spend on walls of burnt brick, and be at expense, than to save with craticii, and be in danger.

After a catastrophic fire in 6 CE, Augustus increased the tax on the sale of slaves to fund a more organised state fire service, perhaps the first of its kind. He also introduced new fire regulations, among them a 21-metre limit on the height of buildings, both to minimise the chance of conflagrations spreading as storeys collapsed and to ensure that water could more easily be transported to upper levels. (Height was also a problem at Grenfell Tower, which stood at 67 metres, while the aerial ladder platforms used by the London Fire Brigade stretch to just 32 metres.)

Cladding and insulation are only the most notorious problems faced by those living in new developments. Lax building regulations mean that careless gaps between cladding and internal walls function as chimneys through which blazes can surge. Timber balconies, arranged like kindling over the cladding (and often used for risky activities like smoking and barbecues) are also implicated. Flammability isn’t the only concern. A survey conducted by Shelter in 2017 found that half of newbuilds have serious and costly structural defects. Some have shoddy mortar that crumbles within months, leaving bricks wobbling like loose teeth. A recent audit concluded that three-quarters of developments shouldn’t have been given planning permission. It will surprise nobody to learn that the Conservative Party receives millions in donations from property developers. The government is neither compelling developers to pay for necessary improvements to buildings, nor is it prepared to do so itself. Many leaseholders, particularly those in shared ownership flats, won’t be able to cover the projected costs. There is a very real risk of bankruptcy.

The point at which we’ll have to reckon with rash, careless building is fast approaching. A recent paper in Nature noted that in 2020 the weight of human-made stuff exceeded living biomass for the first time. (It was just 3 per cent of biomass in 1900.) While trees and other vegetation weigh in at around 900 gigatonnes, buildings, roads and other infrastructure add up to 1100 gt (animals contribute 4 gt, half the weight of plastic on land and sea). There is now more concrete in the world than any other man-made material. After fossil fuels, it is the largest source of carbon dioxide, contributing 8 per cent of emissions, which puts it ahead of aviation and agriculture. Each of its ingredients has a calamitous footprint. Around 2 per cent of all water withdrawn from circulation is locked into concrete, contributing to aquifer stress and drought. Cement production involves intensive quarrying, dust pollution, high-heat kiln combustion and the release of carbon dioxide through calcination reactions. Then there’s sand, which is beginning to run out, triggering vast illegal networks around its extraction and trade. Desert sand is abundant, but its wind-sculpted grains are spherical; it’s the angularity of sea-eroded sand that makes the grains stack and bind so well (the ‘crackle’ that Vitruvius was talking about). Most land sources have been depleted; the dredging of beaches and riverbeds is wrecking marine ecosystems in many parts of the world.

Yet we need more homes. The government claims that its ‘green building revolution’ will hold new houses to higher standards of energy efficiency, leading to a reduction in emissions (improved insulation delivers a large share of that efficiency). They also boast of a six-year low in the numbers of rough sleepers, but this is down to the exceptional measures taken during the pandemic, and ignores the fact that deaths among homeless people rose by a third last year (more than a thousand people died on the streets in 2020). The government’s environmental claims focus too narrowly on the homes once inhabited – the ‘operational’ emissions – while neglecting the colossal ‘embodied’ emissions of the resources extracted and sunk into them. A badly built home may never make good the initial outlay in environmental terms, even if it does tick all the ‘green’ boxes. And there is the cost of all those vacant houses, embodied in bricks and mortar, but also represented by darkened windows, security guards, alarms and paid ‘guardians’: the expensive business of keeping houses empty when there are people who need them.

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