With a raft of developments in engineered timber, architects and designers and increasingly turning to wood as their material of choice. In advance of SCI’s Timber in Construction Materials event, here are five facts about this spectacularly versatile, sustainable material.
1. There’s a super-dense wood that’s as strong as steel, but six times lighter
Liangbing Hu and Teng Li pose with their chemically treated bulletproof wood. University of Maryland
A team at the University of Maryland (UMD), US, have made wood 12 times stronger and 10 times tougher than in its natural form.
Their process consists of boiling the wood in a bath of sodium hydroxide and sodium sulphite, heating it, then subjecting it to compression.
Leading the research, Liangbing Hu, assistant professor in UMD’s department of materials science, said, ‘This could be a competitor to steel or even titanium alloys, it is so strong and durable. It’s also comparable to carbon fibre, but much less expensive.’
The team shot bullet-like projectiles at their super wood to test it – predictably, they blew straight through natural wood, but were stopped by the new material.
The discovery could make even soft, fast-growing woods, such as balsa, more useful in buildings – offering a much quicker carbon payback than slower-growing denser hardwoods such as teak.
The researchers claim the process will work on any kind of timber. Many methods for densifying wood have been tried over the years, such as exposing the wood to steam or ammonia and then rolling it, like a steel bar, but the results have been less than ideal – particularly due to wood’s tendency to expand and contract in response to atmospheric water.
2. It doesn’t have to burn.
You’d be forgiven for associating wood with fire – but engineered timber products such as cross-laminated timber (CLT) have repeatedly demonstrated excellent fireproofing qualities in testing.
The moisture content of timber means that CLT panels char slowly and predictably. This creates an insulating layer that protects the core of the panel, allowing it to maintain its structural integrity for up to three hours.
3. Timber towers are coming
Proposed design for Sumitomo Forestry’s 2041 tower.
Picture a skyscraper. In your mind’s eye, it’s all steel and glass, right?
That’s set to change. Just this month, Japanese timber company Sumitomo Forestry revealed plans for the world’s tallest wooden building in Tokyo. At 350 metres, the proposed skyscraper is taller than any in the country – although taller buildings could crop up before it is built; Sumitomo plans to complete the tower to mark the company’s 350th anniversary in 2041.
The company plans for 90% of its hybrid structure to be wood – a whopping 185,000 cubic metres of timber are planned for use in the ‘braced tube structure’ that features minimal steel – the columns and beams will be hybrid steel and timber, and there will be some additional steel braces in the construction. The tower would contain a hotel, residential units, offices, and shops – surrounded by large, plant-covered balconies.
Today’s tallest timber structure is the Brock Commons Tallwood House, a student residence building at the University of British Columbia (UBC), Canada.
Standing at 53 metres, the 18-storey block was prefabricated off-site, and then constructed in just 70 days. The elevator and stair shafts were made from concrete, but the vertical columns and floor plates were constructed using glue-laminated timber – multiple layers of dimensioned lumber bonded by durable, moisture-resistant structural adhesives.
4. London is home to the world’s largest timber building
Not the tallest – the largest. Dalston Works – a 10-storey, 121-unit housing development in East London, was completed in 2017. You wouldn’t know from it’s outer appearance – it’s clad in brick – but from the first floor upwards, the walls, floors, ceiling, stairs and a lift core are all made from CLT.
It was designed by Waugh Thistleton – a firm that has pioneered use of CLT since 2003. The timber frame offers 50% less embodied CO2 (calculated by the amount of energy required in its production) than a traditional concrete frame, and locks in 2,600 tonnes of CO2.
5. Wood is 100% renewable (as long as it’s sustainably managed)
Unlike bricks and concrete, which rely on the extraction of a finite supply of raw materials, timber is truly renewable – that is, of course, if another tree is planted when one is felled. Timber also does not require the extreme levels of heat used in the production of steel.