New Sydney homes that go up ‘like a Lego kit’

Luigi Rosselli’s new homes often feature rammed earth: a slow, sustainable material affordable only for those with the time to build them, deep pockets to cover labour costs, or both.

Now the Sydney architect, whose clients include 20 of Australia’s richest people, is experimenting with another highly sustainable material on a row of four terraces in Bondi Junction with walls that go up “like a Lego kit”.

Luigi Rosselli is the architect to many on Australia’s rich list and an advocate for sustainable architecture.Credit: Edwina Pickles

Designed as a low-cost version of a terrace, the homes use prefabricated cross-laminated timber (CLT) made from layers of wood stuck together to shrink construction time from “1.5 years [conventional build] to just six months”.

For Rosselli, the build-to-rent project called “CLT with TLC” is a carefully documented experiment to see what can be done with speed and economy to mitigate the housing crisis, increase density and reduce carbon associated with building projects. (He added that the homes would also provide him with retirement income.)

The federal budget included $54 million to accelerate uptake of modern construction methods that are faster and more efficient housing solutions and which reduce carbon.

When Rosselli posted a time-lapse video on Instagram showing the 80-metre square terraces going up on the site of a single-storey home, more than 900 people responded. “Wonderful to see an architect who is usually associated with the highest end of bespoke residential architecture tackling a project like this,” one commenter said.

Using CLT allowed a plan to be easily duplicated, Rosselli said, making it ideal for rapid construction of low- to medium-density housing.

The engineered wood was more expensive than traditional studwork, but it was faster and saved money elsewhere on the build.

“The building industry is slow, and it’s getting slower,” he said. “I’ve worked for 40 years in Australia. We used to build a house in nine months – 12 months maximum. Then it was one year and a half.”

Now it’s two years. This wasn’t the fault of workers, Rosselli said, but increasingly complex regulations, qualification requirements and management of risk and liabilities that often required one trade to finish before another could start.

Luigi Rosselli’s drawing of his new project in Bondi Junction. Credit: Luigi Rosselli

Responding to comments on Instagram, Rosselli said “the big difference is time and accuracy. [it is] six months for the whole project including some traditional trades as tilers and windows. This is more than 50-70 per cent of a standard building site duration. Therefore, substantial reduction of overheads as foreman, insurance, scaffolding and other expensive overheads. Precision is also helping on ordering every out of site item in advance without risk [of] not fitting.”

It was the practice’s first time using CLT. “And I must say, it won’t be the last. It’s really wonderful material. It’s so precise the way they manufacture the cross-laminated timber panels.”

His practice was tracking costs and the project’s impact on the environment. The manufacturer, XLAM, estimates that the use of 173 cubic metres of CLT, made from pine grown in Australian plantations, would store 80.63 tonnes of CO2-eq (carbon) – the same environmental impact as taking 60 cars off the roads.

Architect and sustainability expert Caroline Pidcock said it was “absolutely critical” that designers such as Rosselli led the way with beautiful and sustainable builds. “There is real responsibility because architects look up to them, the press does, and clients do too.”

Rosselli has spent his career trying to educate his clients, many at the upper end of wealth in Australia, on the benefits of using recycled materials.

“The impact that I can have with them is sometimes 10 or 12 times that of a small project,” he said.

“If I can convince a millionaire, a billionaire, to reuse an existing building … it has greater impact. We’ve been quite missionary in trying to convince clients to use rammed earth, which has a very low CO2 component.”

Often he incorporates existing structures. His most famous project so far, the headland at Tamarama owned by David Droga which was recently approved, drew public criticism for the demolition of the old California bungalow called Lang Syne. Rosselli will reuse Lang Syne’s bricks, roof tiles and sandstone.

Designed as a low-cost version of a terrace, the homes use prefabricated cross-laminated timber (CLT). Credit: Edwina Pickles

Monash University professor of practice Karl-Heinz Weiss introduced CLT to the UK market in early 2000 and has been involved in more than 150 projects.

Weiss said unlike concrete, which produces carbon, CLT is made from timber that stores carbon, and was the only sustainable and renewable building material that can be used at scale.

The largest panels were about 3.3 metres by 16 metres. “That gives you speed of assembly because you are not having a lot of little pieces,” he said.

Australia had two factories producing CLT, and others manufacturing glue-laminated beams and components.

Weiss said CLT was typically most suitable for projects from four storeys upwards. Larger projects using CLT, such as the 180-metre Atlassian headquarters, needed concrete or steel for stability.

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