Reading Passage 1: Building Upwards in Wood
For more than a century, the skyline of almost every major city has been defined by two materials: steel and concrete. Timber, meanwhile, was associated with low-rise housing, garden sheds and, in many people's minds, with the devastating urban fires of the past. Building regulations in most countries reflected that association, typically limiting wooden structures to four or five storeys. In the last two decades, however, a new generation of engineered wood products has prompted architects to reconsider those limits, and residential and office towers of fifteen, twenty and even more storeys have now been built largely from timber. Such buildings were once regarded as experimental curiosities; today they are being proposed for schools, hospitals and social housing.
The key innovation is not the wood itself but the way it is processed. Cross-laminated timber, usually abbreviated to CLT, is produced by gluing layers of sawn boards together, with the grain of each layer running at right angles to the one below. The result is a panel that is remarkably stable, resisting the tendency of ordinary timber to warp or split as it absorbs and loses moisture. Panels can be manufactured up to sixteen metres long and are cut to precise dimensions in a factory, complete with openings for windows, doors and service pipes. Because the panels arrive on site ready to be lifted into place, a timber frame can rise far faster than a concrete one, and with a much smaller workforce. On one recent project, a team of a dozen workers was able to complete a full storey in less than a week, a pace that would be difficult to match with poured concrete, which must be left to harden before the next level can be added.
Fire remains the question that every timber project must answer, and the answer is perhaps surprising. A thick timber panel does not burn like a pile of kindling. When exposed to flame, its outer surface chars, and the layer of charcoal that forms insulates the wood beneath, slowing further burning to a predictable rate of well under a millimetre per minute. Engineers can therefore calculate how much additional thickness a beam or wall needs in order to remain structurally sound for a specified period, typically two hours, which is longer than most steel structures without protective coatings can manage. Steel does not burn, but it loses much of its strength at high temperatures and can buckle suddenly; timber, by contrast, fails slowly and visibly. Tests in which full-sized rooms were deliberately set alight have largely confirmed these calculations, although they also showed that exposed timber ceilings can feed a fire once the furniture is burning, which is why many designers still cover some surfaces with plasterboard.
The environmental argument is the one most frequently advanced by supporters. The production of cement alone is responsible for a significant share of global carbon emissions, whereas growing trees absorb carbon dioxide and store it in their wood for as long as the building stands. Advocates calculate that substituting timber for concrete in the structure of a mid-rise building can reduce its embodied emissions, meaning those produced in making and transporting the materials, by up to half. Critics caution that such figures depend heavily on assumptions about forestry practices. If forests are cleared rather than sustainably managed, or if timber is shipped across oceans, much of the benefit disappears. There is also an argument about the end of a building's life: when a timber structure is eventually dismantled, its panels could in principle be reused rather than burned or sent to landfill, extending the period during which the carbon remains locked away.
There are practical obstacles too. Timber is considerably lighter than concrete, which reduces the size of the foundations required, but this lightness creates its own difficulties: wooden floors transmit footsteps and voices more readily, so designers must add layers of insulation or a thin concrete topping to achieve acceptable acoustic performance. Moisture is a further concern during construction, when exposed panels may be rained on before the building is sealed, and insurers in several markets still charge higher premiums for timber buildings because there is limited long-term data on how they perform. As a result, most so-called timber towers are in fact hybrids, with concrete cores housing the lifts and stairwells.
Whether engineered timber becomes a mainstream material will depend less on engineering than on supply and regulation. A large-scale shift would require a substantial expansion of sustainably managed forests and of the specialist factories that produce panels, which at present are concentrated in a small number of regions. Building codes, meanwhile, are being revised gradually as evidence from completed projects accumulates. For now, timber high-rises remain showcases rather than the norm, but each one adds to the body of evidence that a material humans have used for thousands of years may also have a place in the cities of the future.
Reading Passage 2: Designing Out Crime
When people think about preventing crime, they usually think about police officers, prison sentences and the social conditions, such as poverty, unemployment and a lack of education, that are thought to push people towards offending. A quieter tradition, however, has focused on something more tangible: the physical environment in which crimes take place. Its central claim is that the design of streets, buildings and public spaces can make offending easier or harder, riskier or safer, and that relatively modest changes to that environment can produce measurable reductions in crime. This approach does not deny the importance of social factors; rather, it starts from the observation that many offences are opportunistic, and that opportunities are shaped by the places in which people live and move.
The intellectual roots of this approach lie in observations made in the mid-twentieth century about large housing estates. Researchers noticed that crime was not spread evenly across such estates but concentrated in particular kinds of space: long internal corridors, unlit stairwells, and areas of grass that belonged to everyone and therefore, in practice, to no one. By contrast, low-rise housing in which front doors faced the street and windows overlooked shared areas seemed to suffer far less. The explanation proposed was that residents of the second type of housing could see what was happening around them and felt a sense of ownership over the space, so potential offenders felt watched and unwelcome. Later studies refined these early conclusions, pointing out that the estates in question also differed in their management, their maintenance and the incomes of their residents, so design was unlikely to be the only factor.
From these observations, a set of design principles emerged. The first is natural surveillance: arranging buildings, lighting and landscaping so that public spaces can easily be observed by people going about their daily lives. The second is territoriality, which means using fences, paving or planting to signal clearly where public space ends and private space begins. The third is access control, which involves limiting the number of routes into and through an area, so that strangers are more noticeable. None of these principles involves guards or cameras; the aim is to harness the ordinary presence of residents and passers-by. In practice, the three principles overlap: a low front wall, for example, marks a boundary while still allowing residents to see the street.
The evidence for these ideas is encouraging but uneven. Improved street lighting has been associated with reductions in crime in a number of studies, and interestingly, the effect is often observed during the day as well as at night, suggesting that lighting works partly by signalling that an area is cared for, rather than simply by making offenders visible. Closing off the alleyways behind rows of houses with lockable gates has been linked with substantial falls in burglary. Similar results have been reported for car parks, where better lighting, clear sightlines and a staffed entrance have been associated with fewer thefts from vehicles. Yet some interventions have produced disappointing results, and researchers acknowledge that it is often difficult to separate the effect of a design change from other factors, such as changes in policing or in the local economy.
The approach also has its critics. Some argue that designing out crime merely displaces it: if one street becomes harder to target, offenders will simply move to the next. Studies of this question have found that displacement does occur, but it is usually partial, and some research even finds a 'diffusion of benefits', in which nearby areas also experience less crime, perhaps because offenders are uncertain about where the new measures apply. A more serious objection is social. Gated communities, high fences and the removal of benches to deter loitering can make public space less welcoming for everyone, and may disproportionately exclude young people and the homeless. There is also a risk that an emphasis on design allows authorities to neglect more demanding measures, such as youth services or support for people with addictions, which address the reasons people offend in the first place.
In my view, these criticisms are best treated as a reason to apply the principles thoughtfully rather than to abandon them. The most successful schemes tend to be those developed in consultation with residents, who understand how a space is actually used, and those that pursue safety through activity rather than exclusion, encouraging cafés, markets and playgrounds that draw people into a space instead of fortifying it against them. A busy, well-maintained street is, after all, both safer and more pleasant than an empty one, and design that achieves the first by sacrificing the second has misunderstood its own purpose. Design cannot, on its own, solve the problem of crime, but it can make the job of every other intervention a little easier.
