It's cheap and speedy to erect - could timber help solve the housing crisis

8 Aug 2016

Cross-laminated timber has been slow to catch on in the UK but has many benefits such as being light, stable and strong, with a carbon footprint half that of concrete.

Young opportunists often pitch new high-tech materials as the building solution of the future – that is, just before they’re laughed out of the Dragon’s Den. There is, however, one material that is fast building a reputation as a quicker, cheaper and greener alternative to concrete and steel.

One of the world’s tallest timber structures, the Forté building in Melbourne, is 10 storeys high – and yet the structure took 10 weeks to erect. It has been estimated that a concrete structure would have taken another four months.

The residential tower was built by Lendlease using cross-laminated timber (CLT), a natural, renewable material. Sometimes described as super-plywood, it’s formed from layers of timber which are cross laid and glued together to create panels that are light, stable and very strong.

There are substantial speed benefits building with CLT as it is pre-fabricated off-site. Evidence suggests it is 30% faster than conventional construction. But the real selling point is that the production and use of CLT, with low embodied carbon and a zero waste production process, is more sustainable than concrete. The wood’s compact layering provides high levels of air tightness, significantly cutting the amount of energy needed to heat buildings.

Some also argue that timber simply looks better than concrete; it has a softer integration with the landscape and has been proven to prompt a greater sense of wellbeing among residents. Exposed wood in buildings has been shown (pdf) not only to reduce blood pressure and stress levels but also improves air quality through humidity moderation.

After pioneering the high-strength material down under, Lendlease is now bringing its expertise to several of its London projects, including the £2.3bn regeneration of Elephant and Castle; and in Battersea, the company has already delivered 104 homes made entirely from CLT. UK builders are now waking up to the benefits of the low-impact material – there was even an episode of Grand Designs dedicated to CLT and the stylish family home it was used to build.
According to the London Housing Commission, 50,000 new homes per year are needed in the capital just to keep pace with demand. Prices for a new home average almost £500,000. With its substantial cost savings and speedy erection process, could CLT be part of the solution?

Paul King, Lendlease’s MD for sustainability and external affairs, thinks so: “CLT structures are a fantastic sustainable way to provide high-quality, high-density housing. The off-site manufacturing sees tonnes of timber processed at a phenomenal rate every month.

“Because of these properties, CLT lends itself to difficult and complex projects and opens up new avenues of design and development – perfect for large-scale regeneration schemes.”

With the housebuilding industry in the thralls of a chronic skills shortage – which remains one of many factors behind the housing shortage – CLT could help plug that gap since it saves on labour and takes far less time to construct.

The material is 20% lighter than concrete while incredibly clean and quiet to use, and is made from renewable softwoods, which means builders can clock up BREEAM ratings faster than stamp collections. So why aren’t more companies using it?

Lucy Homer, Lendlease’s head of design, said: “UK architecture is still very much attached to traditional building methods and there are perceptions that you cannot build a CLT building of more than six storeys due to the risk of fire. However, we have found that CLT buildings can be built to meet the same fire performance of conventional buildings and, with the right design solution, you should be able to achieve at least 10 storeys with ease.”

In addition, walls made from CLT cannot be exposed externally and the material is equally unsuitable below ground. Concerns have been raised that CLT homeowners won’t be able to obtain mortgages or home insurance; with the exception of Zurich UK, many insurers are shying away because they simply aren’t familiar enough with the product yet.

These limitations mean that it is often more feasible to apply CLT to specific elements of the build. For instance, Lendlease used it to build the structural frames of the townhouses at its Trafalgar Place development in Elephant and Castle.

It is clear that the appetite for CLT is growing. Last year, it was announced that the product was to start being manufactured in the US for the first time. And as CLT residential towers are creeping upwards in height – Sky’s building is currently the tallest timber office structure at four storeys – it’s likely we will start to see the structurally engineered timber making inroads into the commercial sector.

This article has been repurposed with permission from The Guardian UK.