Timber building is increasingly in the news these days, but so far it’s softwood that has grabbed the headlines.
Just last month, The Economist was the latest to latch on to the potential of wood in high rise construction – ‘tall timber towers’ – particularly to cater to mass global urbanisation and the subsequent demand for quick-build, multi-occupancy buildings, with minimal carbon footprint. But the focus was exclusively softwood, or rather engineered softwood.
The press have latched onto prospects for growth of offsite timber-frame in new housing. Again though it’s softwood in the picture. There is one European architect, however, who is swimming against the tide. Boris Zeisser of Netherlands-based Natrufied Architects uses hardwood, and more specifically tropical hardwood, extensively in his projects. And he doesn’t just use it in their more usual applications, such as cladding, roofing, decking, joinery and interiors (which he also does extensively, one of his houses alone featuring seven species). Where it’s suited and the client wants it, Natrufied also employs tropical timber in structural applications, using it visually to complement other wood elements in its free-flowing, naturalistic designs.
Nor, unlike some trade commentators, does Natrufied see tropical timber in building becoming a niche. It uses tropical species for mainstream public and commercial buildings, private and public housing and sees their combination of looks, performance and environmental benefits (which, if sustainably sourced, include helping maintain the rainforest) giving them potential for increasing architectural uptake.
Mr Zeisser had his introduction to building with wood in his first job, in architect Erick van Egeraat’s Rotterdam practice.
“My projects included a concert hall in Breda and a college in Utrecht, both of which used timber. It was in interiors rather than structurally, but included more unusual species, like bamboo and red cedar,” said Mr Zeisser. “Then van Egeraat himself clad his house with padouk, which caused a real stir!” Wood became increasingly ingrained in his work when he and Maartje Lammers set up their own Rotterdam practice, 24H-architecture, in 2001.
An early project was a forest cabin in Sweden called Dragspelhuset, or accordion house. This had a pine-framed extension that concertinaed in when not in use, overcoming planning limits on extension size.
“The forest setting made wood the obvious choice, so we experimented, using an all-wood structure and interior for the first time, with red cedar shingles for the roof and façade,” said Mr Zeisser.
“We just became increasingly attracted to using timber. It has an intense beauty, and invites people to touch, a reaction that’s so rewarding for the architect.”
Subsequent more commercial projects picked up the timber baton and ran with it. The Soneva Kiri resort in Thailand used river red gum for floors, stairs and other timber elements, plus a bamboo frame structure and a variation on rattan for the roofs.
24H-architecture went on to use cumaru for cladding and balcony flooring on a 13-storey block of flats in Nijmegen and sucupira amarela and lauro gamela for joinery and artistic curving, multi-profiled cladding on an eco-community housing project in Leiden.
In the same town they designed Marecollege. This is another multiple species project, using keruing for flooring and lauro gamela and sucupira amarela once more for joinery and cladding.
Mr Zeisser described discovering the potential of tropical hardwoods as a step-by-step process – using them in flooring, joinery and interior cladding leading to exterior decking and cladding, which can be left untreated to age naturally. He first used hardwood structurally on one of the last 24H projects, a private house called Villa van Heurck in Cadzand. This is the project that features seven different tropical species; mahogany and wenge for interior cladding, coromandel for interior furnishings, padouk for sunscreening, afrormosia for window frames and jatoba for doors and flooring, with the latter extending seamlessly under doors and windows outside to become decking.
“We oil the flooring, but leave the decking untreated, so you see the jatoba aging differently,” said Mr Zeisser.
The seventh species is iroko, which comprises the structural frame. “Where we use glulam frames, they’re mostly in larch, but I always put my whole book of timber samples from our main supplier, Vandecasteele in Belgium, in front of clients and, if they choose tropical hardwood and it works, we use it,” said Mr Zeisser.
“The glulam is made by a Netherlands contractor and iroko doesn’t seem to cause them any technical problems in manufacture. The main issue is cost. Its strength means we use less, but it’s still 1.5 times as much as larch. Even so, there are people who want it and we’re now using it for another house in Bergen in the north of Holland.”
Perhaps surprisingly clients rarely quiz Natrufied about the origin of tropical hardwood.
“That’s perhaps because we have a reputation for using it and, in essence, it is exclusively certified timber, so FSC or equivalent,” said Mr Zeisser.
“Sourcing mainly from Vandecasteele also helps as it simplifies our supply chain and they have a very strict policy on sustainable sourcing.”
But Mr Zeisser stresses that he does not use tropical species regardless.
“We aim to build as much as possible in wood, but that could also be softwood or bamboo as well as tropical timbers, which we’ll use with other materials, as well as on its own. It all depends on the project.”
With that proviso and better timber training for architects, Mr Zeisser can envisage more tropical wood building. Even more so if the market understands that, where tropical species are sustainably sourced, creating a healthy market for them incentivises sustainable forest management, while avoiding them can have the opposite effect; leading to tropical forest being converted to other uses, such as palm oil plantations or beef farming.
“That’s how I explain to clients and students why using sustainably sourced tropical wood can be among the most environmentally positive ways of building,” said Mr Zeisser.
“It can help ensure we have tropical forests, rather than fields of cows!”
