An alternative to stick frame construction for homes in Australia using Cross Laminated Timber (CLT)
As Australia looks toward more sustainable and efficient building solutions, Cross-Laminated Timber (CLT) is emerging as a key player in the construction industry and could be a cost effective alternative for the widely used stick frame construction. This article explores an alternative to stick frame construction using cross laminated timber (CLT), exploring the benefits of CLT, the advantages of European spruce (commonly used across Europe for CLT) over fast-grown Australian pine, and the challenges currently limiting its widespread adoption. We also examine CLT’s suitability for different climate zones across Australia and the key considerations for builders and homeowners considering this innovative material.
The Benefits of CLT Over Fast-Grown Pine framing
One of the key takeaways from recent discussions on sustainable timber use is the stark contrast between European spruce and Australian pine. Australian pine, being a fast-growing species, retains a significant amount of moisture within its cell structure. This means that unless it is properly dried or thermally modified, it remains highly susceptible to moisture decay and mould. A striking example of this was seen when a builder stored timber packs wrapped in plastic for an extended period. When they finally opened them, the timber had disintegrated due to retained moisture.
In contrast, European spruce, which grows at a much slower rate, has a more stable and controlled moisture content. This makes it highly suitable for construction, especially in prefabricated timber structures like Cross-Laminated Timber (CLT). The spruce can be dried to around 12% moisture content, creating an optimal internal relative humidity of approximately 40%—a key factor in achieving comfortable indoor living conditions. Fire regulations and perceptions also present hurdles, as CLT’s fire-resistant properties are sometimes overlooked in regulatory approvals, you might be surprised to know that most CLT offerings provide substantial fire resistance levels, reducing the need for additional specialized systems.
The Growing Adoption of CLT in Australia
The benefits of CLT construction are becoming more widely recognised, particularly for its cost savings (can this be referenced? If so, add it in otherwise I wouldn’t be able to substantiate this), sustainability, and efficiency. CLT has been successfully used in Launceston for a six-storey office building, with some sections incorporating Australian hardwood. CLT is an engineered wood product that can be considered jumbo sized plywood, used as a panel product for floors and walls, as opposed to traditional stick framing which takes multiple pieces to create walls, generally on site. CLT however is manufactured in a controlled environment, meaning the speed at which such buildings can be erected is one of its biggest advantages, with a complete structure taking only days instead of months.
Builders and developers are seeing the financial benefits as well. Estimates indicate that a standard construction project costing $2.1 million can be reduced to $1.5 million with CLT, translating to a 30% cost saving (Can you please provide a reference or remove?). Given Australia’s rising labour costs, reducing the on-site construction time by months can make a significant difference. Instead of a large team working on carpentry for nine months, a small crew can assemble the structure in just a few days, primarily using cranes and prefabricated CLT components.
Why CLT Isn’t More Widely Used Yet
Despite these advantages, CLT adoption in Australia has been slower than in Europe and North America. One of the primary reasons is limited local manufacturing capacity. European producers, like KLH, have been at the forefront of CLT production for decades, whereas Australian manufacturers are only beginning to establish themselves. Additionally, the need to import CLT from Europe presents logistical challenges, including container size restrictions and long lead times.
Another factor slowing CLT adoption is the misconception among builders that it requires specialised training. In reality, the erection process is handled by specialised subcontractors who manage everything from shop drawings to transportation and on-site assembly. Whilst builders may not need prior CLT experience, gaining experience and understanding in the construction methodology holds benefits —including a willingness to embrace sustainable and efficient construction methods.
Disadvantages of CLT
While CLT offers many advantages, there are some drawbacks to consider. One of the primary challenges is the higher initial cost compared to traditional timber or steel framing, although overall project costs can be reduced due to faster construction times. Another issue is the limited local supply, as Australia’s CLT manufacturing capacity is still developing. This reliance on European imports increases both costs and lead times.
Moisture sensitivity is another factor, as prolonged exposure to high humidity or improper detailing can lead to swelling or decay, despite certain species used within CLT being more resistant than standard timber. Lastly, while the assembly process is relatively straightforward, proper design detailing and coordination are essential to maximise CLT’s benefits, which can be a barrier for some builders.
Climate Considerations for CLT Use
While CLT offers excellent thermal performance, it is best suited for temperate and cold climates. In Australia, it is most effective in climate zones 5-8, which include cities like Sydney, Newcastle, and Launceston. It is less ideal for tropical and high-humidity regions, where moisture management can be a greater challenge.
Originally developed for the Swiss Alps, CLT performs exceptionally well in colder environments. However, it is increasingly being used in more temperate climates as builders learn how to integrate appropriate moisture barriers and insulation techniques.
Managing Exposure and Moisture During Construction
A common concern with timber construction is exposure to the elements during the build process. Unlike traditional stick-framing, which can develop hidden mould issues, CLT structures are designed to be more resilient, often with special coatings for weather protection. While it’s always recommended to cover exposed structures as soon as possible, CLT can withstand temporary exposure far better than conventional timber framing.
In one extreme case, a CLT structure was left in an exposed state with a parapet wall that inadvertently created a pool of standing water for three months. Once the water was drained and the structure dried out, the project continued without issue. That being said, the general industry recommendation is to get the structure covered within 12 weeks to prevent prolonged exposure.
The Future of CLT in Australia
With the increasing demand for sustainable and cost-effective building solutions, CLT is poised to play a much larger role in Australia’s construction industry. More government and residential projects are incorporating this technology, and as local manufacturing capacity grows, accessibility will improve.
Looking ahead, advancements in CLT production and construction techniques will likely make it a more mainstream choice for builders across the country. While challenges such as supply chain limitations need to be addressed, continued investment in local manufacturing and regulatory adaptation will help unlock CLT’s full potential.
As sustainability becomes a core focus in the industry, CLT stands out as a material that aligns with Australia’s push toward net-zero emissions and environmentally responsible construction. By embracing this innovative material, the construction industry can take significant strides toward sustainability, efficiency, and modern design.