IELTS Academic Reading – Practice Passage 2

Reading Passage

AFor most of the twentieth century, the recipe for a tall building was simple: a frame of steel, floors of concrete, and a skin of glass. Wood, the material humans had built with for thousands of years, was dismissed as old-fashioned and unsafe, fit only for houses and barns. In the last two decades, however, architects and engineers have begun to look at timber again – not the solid beams of the past, but a new generation of “engineered” wood strong enough to raise buildings many storeys high.

BThe material at the heart of this revival is cross-laminated timber, or CLT. It is made by gluing together layers of ordinary softwood planks, with the grain of each layer running at right angles to the one below. This simple trick, borrowed from the way plywood is made, produces large panels that are remarkably stiff and strong for their weight, and that behave predictably under load. Whole walls and floors can be cut from CLT in a factory and delivered ready to assemble.

CMuch of the enthusiasm for timber is driven by the climate. Making cement and steel releases enormous quantities of carbon dioxide; together they account for a large share of the world’s industrial emissions. A growing tree, by contrast, absorbs carbon dioxide from the air and locks it away in its wood. A building framed in timber therefore stores carbon rather than releasing it, at least for as long as the building stands. For an industry under pressure to cut its emissions, that is a powerful argument.

DThe benefits do not end there. Because CLT panels are made in a factory and simply bolted together on site, a timber building can go up far more quickly and quietly than a concrete one, with fewer workers and less waste. The panels are light, which means smaller foundations. Many people also find exposed wood more pleasant to live and work among than bare concrete, and some studies suggest that timber interiors may even lower stress.

ENone of this means the objections have disappeared. The first question everyone asks is about fire. In fact, thick timber behaves better in a blaze than many expect: its outer layer chars and forms an insulating crust that protects the wood beneath, so a large beam can keep its strength for a surprisingly long time. Engineers test these panels rigorously before approving them. Even so, timber buildings must be designed with great care, and the cost of the material remains higher than concrete in many places.

FAround the world, a handful of “plyscrapers” have already risen to prove the point, from apartment blocks to university buildings a dozen or more storeys tall. Yet height remains a limit. Most building codes were written with steel and concrete in mind, and they cap how tall a timber structure may be until more evidence is gathered. As that evidence accumulates, those limits are slowly being raised.

GWhether timber can truly reshape the skyline will depend on more than engineering. The forests that supply the wood must be managed sustainably, so that trees are replanted at least as fast as they are cut down; otherwise the climate benefit disappears. Governments are beginning to update building codes and to encourage timber in public projects. For a material once written off as unsuited to the modern city, it is a striking return to favour.