Cross Laminated Timber (CLT) versus Timber Framing

Exposed cross laminated timber is celebrated in our River project. Photo by Jascha Oakes.

Explore the benefits of Cross Laminated Timber (CLT) over traditional timber framing, focusing on sustainability, cost-efficiency, precision, and biophilic design for modern construction projects in Sydney, Jindabyne & Canberra.

Introduction

As sustainability becomes a central focus in construction, the choice of building materials plays a critical role in reducing environmental impact. Two popular timber construction methods are Cross Laminated Timber (CLT) and traditional Timber Framing. Both offer unique benefits, but their differences can significantly influence the design, functionality, and environmental impact of a building. This blog post aims to guide homeowners, property developers, and architects in Sydney, Jindabyne & Canberra in understanding these construction types, highlighting why CLT might be the superior choice for those familiar with timber framing.

What is Cross Laminated Timber (CLT)?

Cross Laminated Timber (CLT) is an engineered wood product consisting of layers of lumber boards stacked crosswise and glued together. This configuration provides exceptional strength, stability, and rigidity, making CLT an excellent material for a variety of construction applications, from residential homes to large commercial buildings. CLT panels can be used for walls, floors, and roofs, providing a high degree of design flexibility.

What is Timber Framing?

Timber framing refers to both “stick frame” and post and beam timber construction methodologies. Both are traditional construction methods that utilise small and large sections of timber that combine to create a structural framework. This method has been used for centuries and is usually what’s referred to by timber construction. Timber framing relies on precise joinery and can add charm and warmth when left exposed, though this is not common especially in Australia. Timber framing can use either hardwood or softwood species and requires skilled craftsmanship to ensure structural integrity and accuracy. The most common method in ‘modern construction’ is stick framing using small sections of standard pine timber (eg. 90 x 45mm) to create the structural skeleton of a building. In the past, when most timber was milled locally, larger timber members were used as it was more efficient (typically around 300mm sections of hardwood, if available).

Mass timber construction

Stick Frame construction

Similarities Between CLT and Timber Framing

1. Sustainability: Both CLT and timber framing are more sustainable building methods that use renewable resources. Timber is a natural, renewable material that can be sustainably sourced from managed forests. Additionally, both methods help reduce the carbon footprint of buildings, as timber sequesters carbon dioxide during its growth and continues to store that carbon until the timber is eventually destroyed.

2. Versatility: Both CLT and timber framing offer versatility in design. They can be used in a range of building types, from residential homes to commercial structures, and can be combined with other materials to achieve specific aesthetic and functional goals.

Differences Between CLT and Timber Framing

1. Structural Properties: One of the most significant differences between CLT and timber framing is their structural properties. CLT panels are highly rigid and strong due to their cross-laminated construction, making them suitable for larger spans and taller buildings. Timber framing, while strong, relies more on the size and quality of individual posts and beams , which can limit its use in larger structures.

2. Construction Speed: CLT panels are always prefabricated off-site, which can significantly speed up the construction process. Once on-site, these panels can be quickly assembled, reducing construction time and labour costs. Timber framing, on the other hand, requires more on-site work, including precise joinery and fitting of posts and beams.

3. Precision and Accuracy: The prefabrication of CLT panels allows for a high degree of precision and accuracy in construction. This can lead to better quality control and fewer errors during assembly. Timber framing, while also precise, depends heavily on the skill of the craftsmen and can be more prone to variations and imperfections.

4. Aesthetic Appeal: Both methods offer unique aesthetic advantages. CLT panels provide a modern, clean look with the possibility of large, smooth surfaces. The old style timber framing of post and beam construction offers a more traditional and rustic appearance, with exposed beams and intricate joinery.

5. Fire Resistance: Though timber is combustible, CLT panels have some inherent fire resistance due to their solid mass and the charring effect of the outer layers in a fire, which protects the inner structure layers. Timber framing, while also capable of performing well in a fire, generally relies on the size of the outer wall finishes [gyprock]  for its fire resistance.

Biophilic Design: Exposing timber is aligned with biophilic design principles, which emphasise the connection between humans and nature. Exposed wood can create a warm, inviting environment, enhancing the well-being and productivity of building occupants. Whilst the post and beam method of timber framing can achieve some biophilic benefits, exposed CLT would create more biophilic benefits for inhabitants, than post and beam construction, simply due to the amount of exposed timber material.

Exposed mass timber ceiling and handrails at our Mountains project in Jindabyne. Photo by Luke Kneller

Environmental Impact

The environmental benefits of using timber in construction are substantial. Timber has a low embodied carbon, meaning the carbon emissions associated with its production are lower compared to other building materials like concrete and steel. Additionally, timber stores the carbon dioxide that the trees absorbed during their growth, effectively acting as a carbon sink.

CLT and Carbon Storage: One of the key advantages of CLT is its ability to store significant amounts of carbon. According to a study by the University of Washington, using CLT in place of traditional building materials can reduce the carbon footprint of a building by up to 26% (Pei et al., 2012). This makes CLT an attractive option for developers and architects looking to minimise the environmental impact of their projects.

Embodied Carbon in Timber Framing: Traditional timber framing also offers lower embodied carbon compared to concrete and steel. However, the carbon storage capacity is generally lower than that of CLT due to the much smaller volume of wood used.

Biophilic Benefits

Biophilic design aims to connect building occupants more closely to nature, enhancing their well-being and productivity. Timber, with its natural appearance and texture, plays a crucial role in biophilic design.

Health and Well-being: Studies have shown that exposure to natural materials like wood can reduce stress, improve mood, and increase overall well-being (Burnard & Kutnar, 2015). Timber-framed structures and buildings using CLT can both contribute to these benefits, but CLT's potential for larger, more open spaces can enhance the biophilic effect. 

Aesthetic Appeal: The aesthetic appeal of timber is another significant advantage. The natural look of wood can create a warm, inviting atmosphere, making spaces more comfortable and pleasant to be in. CLT, with its large, flat panels, can create expansive, clean surfaces that highlight the beauty of the wood grain. 

Cost Considerations

Cost is always a critical factor in construction projects. Both CLT and timber framing have their cost implications, which can vary depending on the project specifics and whether the project is located in Sydney, Canberra, Jindabyne or elsewhere.

CLT Costs: The initial cost of CLT can be higher than traditional timber framing due to the manufacturing process and the need for specialised equipment. However, the speed of construction and the potential for reduced labour costs can offset these initial expenses. Additionally, the long-term benefits, such as energy efficiency and lower maintenance costs, can make CLT a cost-effective choice over time.

Timber Framing Costs: Timber framing typically has lower upfront material costs compared to CLT. However, the labour-intensive nature of the construction process can increase overall costs. The need for skilled craftsmen and longer construction times can add to the expenses.

Minimising Skilled Labor Requirements with CLT

One significant advantage of using CLT over traditional timber framing is the reduced need for skilled labour. Skilled labour makes up a high proportion of construction costs, and the availability of skilled craftsmen can be a limiting factor in many regions. For example, we have found that in urban areas such as Sydney and Canberra, skilled labour is becoming more expensive, and that in regional areas such as Jindabyne, it can be difficult to find enough highly skilled labour to service the whole industry.

Prefabrication and Assembly: CLT panels are manufactured in a controlled environment off-site, where they are cut and assembled with precision using computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies. This prefabrication process minimises errors and ensures that each panel is produced to exact specifications. Once the panels are delivered to the construction site, they can be quickly and efficiently assembled using cranes and other equipment. This reduces the need for skilled labour on-site and speeds up the construction process.

Labour Cost Savings: The reduction in on-site labour requirements translates into significant cost savings. According to a report by the Forest Business Network, CLT construction can reduce labour costs by up to 25% compared to traditional timber framing (Forest Business Network, 2017). This cost efficiency makes CLT an attractive option for developers and builders, especially in areas where skilled labour is scarce or expensive.

Acoustic and Thermal Performance

In addition to its structural and environmental benefits, CLT offers superior acoustic and thermal performance, which can enhance the comfort and energy efficiency of buildings, whether they are in Sydney, Canberra or the Jindabyne climate.

Acoustic Insulation: The dense, solid nature of CLT panels provides excellent acoustic insulation, reducing the transmission of sound between spaces. This makes CLT an ideal choice for multi-family residential buildings, hotels, and office buildings where sound privacy is important. According to a study by the Building Research Establishment (BRE), CLT panels can achieve sound insulation ratings of up to 50 dB, significantly reducing noise levels in buildings (BRE, 2014). This is, however, reliant on early and detailed acoustic design.

Thermal Insulation: CLT panels also provide good thermal insulation, contributing to the energy efficiency of buildings. The natural insulating properties of wood, combined with the thickness of CLT panels, help maintain stable indoor temperatures and reduce the need for heating and cooling. A study by the University of Graz found that CLT buildings can achieve up to 40% energy savings compared to traditional construction methods (Graz University of Technology, 2016).

Mass timber on show at our River project. Photo by Jascha Oakes

Higher Quality Buildings with CLT

The precision and accuracy of CLT panels result in a higher quality building than traditional timber framing. This precision is achieved through the use of advanced manufacturing technologies and computer-aided design.

Precision Manufacturing: CLT panels are manufactured in a controlled environment using state-of-the-art equipment that ensures each panel is cut and assembled with exacting precision. This level of accuracy reduces the likelihood of construction errors and ensures that the panels fit together perfectly on-site. Most manufactures guarantee a millimetre level of accuracy. 

Improved Quality Control: The controlled manufacturing process allows for rigorous quality control measures to be implemented, ensuring that each CLT panel meets the highest standards of performance and durability. This reduces the risk of defects and improves the overall quality of the finished building.

Enhanced Structural Integrity: The cross-laminated construction of CLT panels provides enhanced structural integrity, making buildings more resilient to environmental stresses such as wind and earthquakes. This results in buildings that are not only more durable but also safer for occupants.

Sustainability and Repurposing of CLT

Another key advantage of CLT is its sustainability, particularly at the end of a building's life. Unlike traditional timber framing, which often ends up as waste, CLT can be repurposed and reused, further reducing its environmental impact. 

Repurposing CLT Panels: At the end of a building's life, CLT panels can be dismantled and repurposed for other construction projects. This extends the life of the material and reduces the demand for new resources. The durability and structural integrity of CLT panels make them ideal for reuse in new buildings, contributing to a circular economy in the construction industry.

Reduced Waste: The ability to repurpose CLT panels reduces the amount of construction waste that ends up in landfills. This not only helps conserve natural resources but also reduces the environmental impact associated with waste disposal. Mass Timber manufacturers often create other useful products with the waste that is created, including making use of off-cuts all the way through to creating pellets!

Case Studies: CLT and Timber Framing in Australia and New Zealand

CLT in Tall Buildings: One notable example of CLT's application in tall buildings is the Forte Building in Melbourne, Australia. This 10-story residential building was the world's tallest CLT building at the time of its completion. The use of CLT reduced the construction time by 30% compared to traditional methods and significantly lowered its carbon footprint (Green Building Council Australia, 2013).

CLT in Education Buildings: The NMIT Arts & Media Building in Nelson, New Zealand, is another excellent example of CLT in construction. This award-winning building showcases the versatility and strength of CLT, with its innovative design and sustainable construction practices. The use of CLT reduced construction time and minimised waste, demonstrating the efficiency and environmental benefits of this material (WoodWorks NZ, 2016).

Timber Framing in Historic Buildings: Timber framing continues to be a popular choice for restoring and preserving historic buildings in Australia and New Zealand. The use of traditional joinery techniques and the aesthetic appeal of exposed wooden beams make timber framing ideal for maintaining the character and integrity of historic structures. The restoration of the Riebeek Street Cottages in Perth, Australia, showcases the enduring appeal and durability of timber framing (Heritage Perth, 2020).

Conclusion

Cross Laminated Timber (CLT) and traditional Timber Framing each offer unique benefits and can be suited to a variety of building projects. CLT's strength, precision, environmental benefits, and reduced labour requirements make it an excellent choice for those looking to modernise their construction approach while reducing their carbon footprint. On the other hand, timber framing's aesthetic appeal and traditional charm make it a timeless option for custom homes and smaller projects.

For homeowners, property developers, and architects familiar with timber framing, considering the use of CLT can open up new possibilities in design and construction whether in Sydney, Jindabyne or Canberra. Utilising more timber by using CLT instead of traditional timber framing is a wonderful way to introduce biophilic benefits to a building and lower its embodied carbon, making it a sustainable and forward-thinking choice.

By understanding the similarities and differences between these construction methods, stakeholders can make informed decisions that align with their project goals and environmental values.

Brother Nature provides a specialist mass timber design and build service in Sydney, Jindabyne and Canberra. Reach out now to discuss your upcoming project.

References

This Article was written with the help of AI.

Burnard, M. D., & Kutnar, A. (2015). Wood and Human Health. Annual Review of Wood Research, 10(1), 77-88.

Forest Business Network. (2017). CLT Construction Reduces Labor Costs. Retrieved from forestbusinessnetwork.com.

Green, M. (2017). The Brock Commons Tallwood House: Pioneering Tall Timber Buildings. Wood Design & Building, 10(2), 24-29.

Pei, S., Rammer, D. R., Popovski, M., Williamson, T., Line, P., van de Lindt, J. W., & Dolan, J. D. (2012). An Overview of CLT Research and Implementation in North America. Proceedings of the World Conference on Timber Engineering.

Building Research Establishment (BRE). (2014). Acoustic Performance of Cross Laminated Timber. Retrieved from bre.co.uk.

Graz University of Technology. (2016). Energy Efficiency of CLT Buildings. Journal of Sustainable Architecture and Civil Engineering, 12(3), 45-53.

Green Building Council Australia. (2013). Forte Building. Retrieved from gbca.org.au.

WoodWorks NZ. (2016). NMIT Arts & Media Building. Retrieved from woodworksnz.com.

Heritage Perth. (2020). Riebeek Street Cottages Restoration. Retrieved from heritageperth.com.

Fairbanks House. (2020). The Oldest Timber-Framed House in North America. Retrieved from fairbankshouse.org.