1. Introduction
Although timber has been used in construction for millennia, the interest in mass timber construction (MTC) as a construction technique has grown in the past decades [1]. Mass timber construction products (MTCPs) have been considered as an alternative to more carbon-intensive construction materials, such as concrete and steel, due to increased awareness of their adverse environmental impacts (including the depletion of natural resources and emissions of greenhouse gas (GHG)) [2,3].
Mass timber construction (MTC) is an innovative method that utilises engineered timber products (massive wood planar or frame elements) as the primary material for core building elements such as walls, columns, and beams [2,4]. MTC is typically used in applications as a substitute for wet-poured steel-reinforced concrete, solid section ‘tilt-slab’ concrete, and steel framing. Thus, it is ideally suited to low- to medium-rise structures [2].
Building and construction activities account for 36% of global final energy use and 39% of energy-related carbon dioxide (CO2) emissions—one of the critical reasons for global climate change [5]. In response to tackling global climate change (restricting global temperature rise by 2 °C) and ensuring future sustainable development, countries around the globe have agreed upon a long-term strategic direction guided by the ‘net zero emission by 2050’ and Sustainable Development Goals (SDGs, also known as Global Goals) [5,6,7]. Although sustainable cities and communities (SDG 11) and climate action (SDG 13) seem to be more relevant for construction activities, the construction sector is directly and indirectly linked with all 17 SDGs [8].
Similar to many other countries, brick, steel, and concrete are widely used for the building envelope in Australia. These materials produce the most significant embodied emissions during production and service life compared to other materials such as timber and rubber [9]. According to Li, Rismanchi, and Ngo [10], timber has relatively low thermal conductivity, reducing energy use for heating and cooling in the Australian climate. Therefore, selecting suitable materials and construction methods for construction is vital to reducing GHG emissions.
However, with advancements in mass timber technology, MTC is increasingly employed in high-rise structures such as the 2019 mixed-use building Mjstrnet (Brumunddal, Norway). Other examples include the Atlassian Sydney headquarters, a 40-storey hybrid timber structure with 100% renewable energy supply, the 98 m Wohnhochhaus (WoHo) in Berlin, Germany, and the most ambitious MTC project (W350 in Tokyo, Japan), a 70-storey (350 m) high-rise building [11,12,13,14].
Based on bonded mechanism, MTCPs are mainly divided into two categories: (i) glued MTCPs (e.g., glued laminated timber (GLT), structural composite lumber (SCL), including laminated veneer lumber (LVL) or cross-laminated timber (CLT), etc.), and (ii) non-glued MTCPs (e.g., dowel-laminated timber (DLT), nail-laminated timber (NLT) and cross nail-laminated timber (CNLT); and interlocking cross-laminated timber (ICLT)) and MTPs [4]. The application of MTC in Australia is predominantly limited to CLT, LVL, and GLT [15]. As a sustainable building material, the CLT market worldwide is growing rapidly. However, given the USD 350 billion Australian construction industry, MTC is still in its early days of market penetration [16].
Several studies reported that a lack of supply chain of MTCPs (including forestry and local manufacturers), reluctance to change the entrenched building techniques and materials (e.g., trust in double-brick construction), and weak regulatory requirements to restrict emission and environmental degradation in the construction industry are the key reasons for not adopting MTC as a mainstream construction technique in Australia [2,15,17]. However, the application of CLT is expected to be increased in the Australian market due to the opportunities of sourcing CLT materials from local manufacturers, as XLam started to manufacture in Albury in NSW in 2019, and Timberlink Australia is planning to complete a new facility in the Green Triangle (South Australia and Victoria) in 2023 [18].
Although the sustainability benefits such as low embodied emissions are often referred to as advantages of MTC, it also offers competitive construction costs depending on project type and scale [15,19]. For example, a study revealed that MTC projects in Sydney, Australia, had lower costs (2.2% for eight-storey apartments, 12.4% for seven-storey office buildings, and 13.9% for two-storey aged-care facilities) than the alternative n¬on-timber solution [15]. However, despite various reported benefits and opportunities of adopting MTC in the construction industry, the update in Australia is stagnant. A better understanding of the MTC project scope, project size, and building typology would provide competitive advantages to the client and the developer/builder in promoting MTC over traditional construction. Therefore, this study intends to draw the appropriate project and building type by analysing the global best practices in MTC. Furthermore, this study investigates the application of MTC in the global context to better understand timber products and projects through their key characteristics and applicability in the Australian industry context. The investigation aims to analyse the perceptions of widespread application of MTC in the context of industry practitioners in Australia. The study focuses on the following key objectives:
i.. explore key characteristics of MTCPs and project scopes based on a brief review of global MTC projects;
ii.. identify barriers and opportunities in the widespread application of MTC in Australia through a perception analysis of the industry experts;
iii.. propose recommendations for overcoming the barriers to adopting MTC in Australia.
2. Materials and Methods
The study applies a mixed methodological approach to achieve the research objectives and overarching aim of the study. The key characteristics of the MTCPs and projects scope are analysed using a literature review of the global practices (presented in Section 2). The identified characteristics of the MTCPs were used in developing the questionnaire survey to conduct the perception analysis of the industry practitioners, along with focus of identifying the key barriers and opportunities for the widespread application of MTC in Australia (presented in Section 3). The industry expert interviews are conducted to validate (presented in Section 3) and formulate the framework (Section 4) to overcome the barriers in adopting MTC in Australia. Figure 1 shows the applied methods of the study.
As part of the literature review, study considered the selected MTCPs as the global best practices to analyze the development of mass-timber construction and products. The study compiles the key characteristics of the MTC and MTCPs from the global best practices (covering scholarly database as well grey literature including reports) and then use them to formulate the survey questionnaire to conduct the perception analysis of the industry practitioners in Australia. A total of 38 industry practitioners participated in the survey and provided their feedback through the online survey. The identified key challenges, barriers, and characteristics of MTC and MTCPs were further validated for the Australian context through expert interviews of the industry practitioners. A total of eight experts were interviewed, and the key findings from the survey and interviews were then used to formulate the critical enablers of the widespread application of MTC and MTCPs in Australia.
2.1. Literature Review
As one of the major emitters of GHGs, the construction industry is pressured to reduce GHG emissions [7]. The construction industry generated the most carbon (10 GtCO2 or 28% of total world energy-related CO2 emissions) [5]. The rising global need for new housing and infrastructure will result in increased building activity over the next decades. However, the construction industry’s yearly improvement rate has slowed, with a concurrent increased focus on CO2 reduction initiatives [5]. Due to land scarcity, concrete and steel structures aim to reach new heights. Despite its high embodied emissions, concrete has been the most extensively used construction material for decades. Conversely, timber is a renewable resource that requires little energy to extract and manufacture and can sequester carbon. Thus, widespread MTC use may significantly cut carbon emissions and help achieve net-zero emission ambitions [20].
2.1.1. The Development of MTC Technology
CLT is the most common mass timber product (MTP). The application of CLT as an alternative to steel and concrete in multi-storey residential buildings has been widely used in Europe since the 1990s [21]. CLT is a product of a PhD research completed in 1994 by Austrian-born researcher Gerhard Schickhofer [22], which paved the way for the mass acceptance of engineered timber in the European building industry. By the early 2000s, manufacturing and construction techniques had matured enough for full-scale production in Europe [23]. By 2015, 60% out of 80% of global CLT was produced in Austria, and the remainder was contributed by Germany and Switzerland [24]. Germany, Austria, Switzerland, Italy, and the UK were identified as the most significant consumer markets for CLT, absorbing 70% of European CLT production output [25]. The availability of wood, and the well-established wood industry in Europe (produced around 488,603,000 m3 of Roundwood in 2020) played a significant role in promoting MTC technology in Europe [26]. In comparison, the total log harvested in Australia was 32,939,000 m3 in 2017–2018 [27].
Other than Europe, CLT manufacturing in the USA, Canada, and New Zealand started at around the same time. Canada-based companies Structurlam and Nordic Structures have been producing locally sourced CLT panels since 2010 (with a production capacity of 110,000 m3), and in the USA, CLT manufacturing started with SmartLAM in Montana in 2012 [28]. The first CLT line in New Zealand was built in 2010 (the current capacity is 60,000 m3), and New Zealand CLT capacity is expected to grow up to 500,000 m3 by 2024 [25,29,30]. XLam launched the first CLT manufacturing plant in Australia in 2018 with a capacity of 60,000 m3 [29].
A recent Cross Laminated Timber (CLT)—Global Market Trajectory & Analytics claimed that the global market for CLT, estimated at USD 992.4 million in the year 2020, is projected to reach USD 2.5 billion by 2027, with a growth rate of 13.9% during 2020–2027 [31]. The same report also predicted that the highest growth would be observed in China at 18.2%, followed by Canada and Germany at 12.2% and 11%, respectively.
2.1.2. Mass Timber Products and Building Systems
Mass timber building (MTB) systems can mainly be categorised into two different types, lightweight timber framing and mass timber framing. Currently, different types of MTPs are available. The available width and size vary; however, the commonly available thickness of the MTPs is up to 325 mm, width up to 3000 mm, and length up to 24 m [32]. Table 1 shows the different types of mass timber building systems.
2.1.3. The Key Characteristics of Mass Timber Products (MTPs)
Mass timber products (MTPs) have excellent fire resistance and can be predicted when exposed to fire; because CLT and other MTPs have thick cross sections, the outer layers of MTPs can form a carbon layer as a barrier to the inner layers. Most MTPs have a similar nominal char rate of approximately 1½–1¾/60 min [32]. The fire performance of MTPs can also be enhanced by drywall lining or additional walls and floor coverings. As per the International Construction Code (ICC), MTC buildings require the fire resistance of exterior walls, and the structural frame is 2 h and 1 h, respectively [36]. In the case of gypsum-protected lightweight wood-framed assemblies ranging from 30 to 120 min [37]. Timber has low thermal conductivity, with limited heat transference between internal and external buildings. Its higher insulation properties can significantly reduce energy use and waste [38].
MTPs are denser than lightweight timber, reducing cooling and heating costs. Like other building approaches, MTC does not solely depend on materials to produce the desired acoustic performance. As with any other building construction process, appropriate acoustic measures should be taken to reduce unwanted noise. Density is the primary factor that contributes to the strength of timber products. The density of mass timber products can be increased through existing manufacturing technology of engineered timber [39]. Hence, the stiffness of the MTPs may be measured reliably for its application in building structures. In NLT and GLT products, around 0.25% change in dimension for each 1% change in moisture content.
2.1.4. The Key Characteristics of the Global MTC Projects
The following section analyses MTC projects from global practices to understand projects’ characteristics. The projects are selected based on the project types, geographical locations, and available information sourced from scholarly and grey literature. From Appendix A, it is apparent that MTC is applied in different project types, including residential, commercial, institutional, and public buildings. In addition, the height of the projects varies from single-storey academic buildings to proposed 70 storeys of mixed-use buildings with a hotel, residential units, and commercial spaces. The most frequently reported key benefits include the reduced-environment impact related to GHG savings (carbon neutral to carbon-negative buildings), low-embodied materials, and a short duration for the onsite timber construction and installation activities. Several projects reported cost-competitive scenarios; however, the opposite (e.g., Tamedia project) is also reported. CLT is the commonly used MTP and GLT, glulam, LVL, and DTL are also used in different projects. The MTC projects used 100% timber (e.g., Miyamura Veterinary Clinic) to a hybrid technique using concrete foundation or steel structure (e.g., Forte, Wynn Williams House, etc.). Building heights are often reported as one of the critical challenges for MTC. However, it is evident from the global application of MTCPs that MTC has already been applied to 18–20 storey mixed-use buildings, and the proposed height for future projects is up to 70 storeys. Hybrid solutions combining timber with steel and traditional concrete foundation seem to be the practical solution to achieve the desirable building heights for MTC tall building projects.
2.2. Data Collection Tools
The study applies a mixed-method research approach. Both quantitative and qualitative data are carried out and analysed for the study. The study follows mainly three methodological approaches to achieve the study objectives:
a brief review of global MTC projects to analyse the key characteristics of MTC products and projects and their applicability in the Australian context;
a perception survey to identify project typology, barriers, and opportunities in the widespread application of MTC in Australia;
expert interviews to validate survey findings and frame the recommendation to overcome identified barriers in Australia.
Selected global MTC projects were analysed as presented in Appendix A. The questionnaire is designed to collect quantitative and qualitative data using both open-ended and closed-ended questions. The data was collected using a snowball sampling technique. Questionnaire surveys were distributed among industry professionals, including builders, structural engineers, architects, timber suppliers, and developers in Australia. The survey was distributed online to approximately 860 professionals in Australia on 2 September 2021, and the survey was closed on 20 October 2021. The study secured ethics approval (HRE2021-0523) to conduct the survey and interview. Only 51 experts participated in the survey. Unfortunately, 13 of the surveys were incomplete. Thus, the study only considers a total of 38 completed questionnaire surveys. The response rate was only 5%, which is very low. It is important to acknowledge that the survey was conducted in the middle of the COVID-19 outbreak, when the construction industry was already under stress. However, the authors acknowledge the data limitations in the survey as well as interviews.
Eight industry specialists were interviewed. Despite just eight experts being questioned, the interview reached saturation point with comparable material being shared. Mass timber construction is relatively new in Australia. Ten questions were presented to enable respondents to express their thoughts on the problems and prospects of MTC applications in Australia. The interview recordings were transcribed from audio recordings. Re-identification coding was allocated to all respondents. The expert interviews validated the survey results and identified priority areas for mass timber construction suggestions in Australia. In addition, an industry-funded organisation representing all aspects of the timber sector was interviewed. While these interviews confirmed much of the survey and expert data, they also revealed new ideas worth exploring.
3. Results and Discussion
3.1. Demographic Data of the Survey Respondents
A total of 51 people participated in the survey; however, only 38 respondents (N = 38) have completed the survey. Incomplete surveys were excluded from the study to maintain data quality and consistency. As expected, the demographic background of the p varies. Builders and developers represent the highest (38%), followed by consultants (36%), and contractors (14%). The roles of the respondents vary from a single role to multiple roles, as reflected in the survey (42 roles, whereas the respondents were 38). The study was focussed on the industry practices, and thus academia was not part of the survey and interview, which is a limitation of the dataset presented in the study. Given the importance of the industry practices and perceptions of the industry practitioners, the authors strongly believe that the findings of the study will provide a valuable insight of the barriers and enablers of MTC and MTCPs in Australian from the context of the industry practices.
The respondents (N = 38) represent the different company sizes: small (21%), medium (32%), and large (47%). The average level of experience working in the construction industry is high; around 70% of the respondents have over 5 years of experience, and over 50% of the respondents have over 10 years of experience. Table 2 shows the key demographic data of the survey respondents.
3.2. Demographic of the Expert Interviews
The researcher who conducted the interviews transcribed the conversations with eight building industry specialists from various companies, including engineering consulting firms, architecture and planning companies, builders, and MTC manufacturers. The average experiences of the interviewees were 12.6 years, representing an expert group. Table 3 shows the affiliation, company size, and the level of experience of the experts. The authors acknowledge that the focuses of the interviews were to validate the findings from the literature review and questionnaire survey, and to formulate the framework of key enabling factors in widespread application of MTC in Australia. There was only interviewee who also had affiliation with a university; otherwise, all experts represent the architecture, engineering and construction (AEC) industry in Australia, and this could be a limitation of the study.
3.3. Survey Respondents’ Prior Experience with MTC Projects
Only 26% of the respondents (N = 38) had prior experience working with MTC-related projects, and the majority (74%) of respondents had no prior experiences with MTC. However, despite a lack of prior experience, the level of knowledge fairly represents the industry, with around 53% of respondents with a high to very high level of knowledge about MTC technique. The remaining 47% of respondents had limited knowledge (low to very low). The residential projects (44%) were the major constituents of the previous MTC projects (N = 18) followed by commercial (22%), public (22%), and industrial (12%) projects.
The experience of working with MTPs is higher, and around 23 respondents (60%, N = 38) have prior experience in working with MTPs. The respondents (N = 23) reported that CLT (30%), LVL (30%), and GLT (22%) were the most widely applied MTC technology in Australia. However, the respondents also reported using NLT (9%), DLT (4%), and PSL (4%) in their past projects. The application of MTC (N = 37) varies from beam (24%), floors (22%), columns (14%), shear wall and diaphragm (14%), core and shafts (11%), interior (5%), cladding (3%), and others (8%). It is also evident from the practitioners’ interviews (interviewee 1, 3, 6, and 8, 2021) that CLT, LVL, and GLT have the market penetration and wide application in the Australian construction industry.
3.4. Knowledge of MTPs
Figure 2 indicates the level of knowledge of the MTPs of the respondents who had no prior experience working on MTC projects (N = 28). The level of knowledge was assessed in four different levels: no knowledge, low (I heard about it), average (I know the product), and high (I know how to apply it). It is evident that respondents have very limited knowledge (no knowledge—just heard about it) of most of the MTPs, except for LVL (m = 3.04), GLT (mean value of 2.75), and CLT (m = 2.61). As reported in the previous section, LVL, GTL, and CLT are commonly used MTPs in Australia, so the respondents are aware of these MTPs.
It was suggested by one expert interviewed that the main area for using this methodology in WA was in the construction of single- and double-storey residential buildings. This was expanded by (interviewee 08, 2022), who suggested that the optimal use in buildings was in light-weight applications and buildings up to eight storeys; however, most design sentiments seemed to be around ‘how tall can we go’, which is not the correct approach to attain the best use nor most economic use of the material.
However, clients were described as typically ‘passive’ in their knowledge of what CLT or LVL was. Moreover, the expert argued that there was limited engineering expertise in WA with the capacity or capability to do CLT building, and ‘what is available, what expertise the builders and engineers have, is all driven by market forces’ (interviewee 01, 2021). It must be remembered that CLT has only been a common term in Australia for around 10 years, which would contribute to this (interviewee 08, 2022).
3.5. Benefits of MTC Projects over Traditional Construction Projects
Figure 3 highlights aspects that respondents felt were key performance factors that differentiated MTC over traditional construction, with the highest mean values in the areas of structural performance and connections (m = 3.6), environmental performance (m = 4.11), thermal performance and energy efficiency (m =3.8), timesaving (m = 4.2), and design flexibility (m = 3.6). Fire (m = 2.8) and moisture performance (m = 2.89) were considered lower performance indicators when compared with traditional construction. According to expert interviews, the perceived performance attributes or unmet deficiencies in MTC projects over traditional construction stem from a lack of knowledge of industry experience (interviewee 01–06, 2021), a lack of promotion of the construction methodology (interviewee 04, 2021), and insufficient university education in the field (interviewee 01–06, 2021). Moreover, a lack of knowledge of future material trends and the potential for timber hybrid suggests a critical need for upskilling and education (interviewee 04 and 05, 2021).
3.6. Key Characteristics of Suitable MTC Products and Projects in Australia
The study reveals that the highest level of suitability of MTC as a construction methodology, according to respondents (Figure 4a), was in public building infrastructure, with 29%, followed by residential (28%), and commercial construction (21%). At 3%, respondents considered industrial settings as least suitable, while 19% suggested that MTC was unsuitable in all settings.
3.7. Suitable Heights for MTC
Figure 4b highlights that the majority of the respondents (67%) considered low- to medium-rise (up to 5 storeys) as the most suitable for timber construction, and 30% considered 6 to 20 storeys as the most suitable, while 3% thought that 20 storeys and above were suitable. Interviews (05–08), however, elaborated on smaller projects in terms of size/height, suggesting that there was little benefit from an ‘economies of scale perspective’, but that medium scale provided opportunities for significant benefit, and large scale posed many more challenges (interviewee 02, 2021). Interviewee 5 emphasized that cost is often not a consideration for a small, residential construction, because there are specific groups of customers who want to use mass timber in their project, and thus design flexibility and construction approaches are the key consideration, rather than the project cost. This could be relevant for a specific group of customer, but not all; particularly for the widespread application, cost is a major factor.
3.8. MTC Project Scale
Figure 4c shows the value contribution of MTC construction material and methodology from the position of project vale. Project scale defined by way of value highlighted similarities across survey respondents and expert interviews. Surveys outline that 33% of respondents (N = 31) viewed medium-scale projects (in terms of value defined as USD 3 m–USD 10 m) as best suited to MTC projects. Furthermore, 29% suggested large scale (USD 10 m–USD 30 m) was suitable, while 25% thought small scale (USD 1 m–USD 2 m) was appropriate.
While it is necessary to grasp the advantages and disadvantages of various materials’ limitations, respondents suggested these were offset by steel and timber hybrids, or concrete and timber hybrids, which interviewees mentioned are likely to be the likely next stage towards increasing capabilities. Hybrids are already starting to emerge for high-rises—some 20 to 50 floors high (interviewee 05 and 07 2021). Hybrids are also evident in the global MTC projects. These require lengthier engineering and approval processes. Focus areas of technical and performance limitations are outlined in Table 3 and Figure 4, which comprise format size (production/fabrication) limitations and performance. Performance criteria that had the largest standard deviation amongst respondents were fire resistance (std dev = 1.05) and rotting (std dev = 1.03).
3.9. Critical Technical/Material Limitations of MTC
Table 4 shows the critical technical and material limitations of MTC projects. Respondents (N = 38) identified only the size constraints of the panels, and the internal vs. external application and interoperability with other systems, as technical and material limitations (mean value less than 3).
In total, 37% of respondents ‘Agreed’ that internal versus external applications of MTC was a limitation, while 37% ‘Agreed’ or ‘Highly Agreed’ that format size (production/fabrication) was a critical limitation in Figure 5. Interviewees drew on appropriate applications to work with some of the limitations discussed; for example, Class 1 structures and projects with a straightforward design, such as rectangle structures, were considered appropriate, according to interviewees. MTC products (firewalls) with panel fire ratings were suggested to be appealing in townhouse applications. In contrast, in Class 2 applications, the influence of the architectural arrangement, which might be a regular grid pattern or a typical floor plan layout, contributed to the feasibility. Interviewee 05 (2021) posits that ‘student accommodations are very suitable based on the floor plan… many rooms in a very tight space’, thus it appears to be ideal based on a smaller repeatable floor design, although large commercial developments offer opportunities for efficient usage if a regular grid pattern is maintained. If the same technique is used, university buildings may also be cost-effective.
3.10. The Main Barriers to Widespread Acceptance of MTC
Table 5 and Figure 6, together, highlight that ‘Lack of local manufacturers’ and ‘Lack of local suppliers’ were cited by survey respondents (N = 38) as the two main barriers toward widespread acceptance of MTC, and offered the least disagreement (std dev = 0.74 and 0.78, respectively). Interviewee 02 (2021) supported this, attesting that ‘not being able to get a local supply that easily’ is a barrier, whereas, interviewee 05 (2021) mentioned that ‘mass timber is very much a part of the international supply chain… (that) the huge construction boom in Europe and North America had much impact (in Australia)… a lot of timber shortage at the moment, not a function of the local manufacturing’.
However, interviewees 07 and 08 (2022) suggest that supply from Europe is coming back online, which was restricted due to COVID for some time; thus, supply should not be an issue. Typically, the US demand for the European stock is very high, while Australia’s demand is much smaller, but is increasing; therefore, ‘Timberlink’, a new Australian supplier, will be in the marketplace around 2023. This will triple the size and capacity of timber production for construction in Australia (interviewee 07, 2022). Therefore, if there were to be an increase in demand, there would be sufficient capacity, and as a result, the price is likely to become increasingly competitive. An area of uncertainty surrounded public liability insurance, with 58% of respondents selecting that they were ‘Unsure’ if this category was the main barrier to acceptance. Next to this, a ‘Lack of demand/market’ (std dev = 1.04), ‘Unskilled labour’ std dev = 1.02), and ‘Higher project/maintenance cost’ (std dev = 1.12) feature as areas of difference in sample agreement, while ‘Durability and quality of materials (fire resistance, noise, moisture, etc.)’ also continues to separate respondent feedback.
The main barriers outlined by interviewees were the lack of competition (monopolisation) driving higher costs. Interviewee 01 (2021) stated that CLT construction ‘is not cheaper (nor) less expensive, and it is not low quality’, and that cost cannot be a ‘reason why a building is built in CLT. If you think that one of those reasons is cost, then don’t do it’. Furthermore, a lack of education and awareness, and unfounded concerns around limitations, such as fire, persisted. For example, interviewee 02 (2021) suggested a ‘general lack of understanding in the Australian industry. In North America and Europe, there is a great degree of understanding… People don’t understand fire here either…fire engineer(s), like in any industry will have different opinions… some are very conservative, and others more pragmatic providing many different fire engineering solutions’. Other performance criteria were also mentioned. Interviewee 04 (2021) cited ‘challenges (and) misconception around timber… you know, timber gets wet and going to get rot, and doesn’t last that long, it is going to catch fire, and all sort of different things… and that is just through lack of education’.
With this lack of industry experience (nationally) and the need for industry upskilling, immediate attention was required. Moreover, traditional materials used in the industry and trades that align with them make it difficult and resistive to change (interviewee 07 and 08, 2022).
Of the respondents who answered this question, Figure 6 indicates that 24% suggested that transportation was a fundamental challenge to overcome at a project level. According to interviewees, this arose from the position of high transport costs, depending on location and panel size. According to interviewees, steel can be bolted and welded onsite to greater lengths, while concrete, on the other hand, simply necessitates additional formwork, and then sufficient local batching and pouring follows. Timber, it was suggested, is unique in that it is extremely ‘difficult to move slice timber beams’ (interviewee 02, 2021) and ship overseas (to and from Europe). This, for example, presented a limitation to 12 m stock length; larger lengths may be conceivable but would require the use of non-standard container sizes. As a result, this would need specific processing, handling, and wrapping. If it is manufactured in Australia, those interviewed mentioned that the longest conventional production size is 12m, and transportation by truck beyond 16m could be achieved (interviewee 02, 2021). It was suggested that this would be difficult—a significant constraint; thus, creativity in design, construction, and grid layout was more imperative in timber construction projects. Skilled labour, with 23%, closely followed transportation as a key project-level challenge, which was supported by themes drawn from the interview data.
3.11. Project-Level Challenges
Figure 7 presents the project-level challenges of the widespread MTC in Australia. The transportation issue, skilled labour, and assembly seem to the top three major challenges.
Figure 8 presents what respondents stated were the key opportunities, strengths, and competitive advantages of MTC in the Australian Market. When weighing up the mean score with standard deviations for each criteria, featuring the highest, key areas included: high embodied carbon 47% (mean = 1.89: std dev = 0.89), Adaptable/flexible design (mean = 2.27: std dev = 0.86), and Opportunities of circular design (e.g., design for reuse/recycling) (mean = 2.13: std dev = 0.92). Supporting forestry and renewable sources 42% with a mean of 1.97 (std dev = 0.93) also features as a key opportunity.
3.12. Pathways to the Widespread Adoption of MTC in Australia
As a contemporary building process, MTC has several advantages over traditional construction methods in terms of sustainability. The research indicated that practitioners still have misconceptions about MTC safety and standards, which prompts clients to believe MTC is not a suitable approach. Yet, MTC product specifications frequently satisfy Australian regulations for fire and insulation. Due to advancements in MTC technology and the availability of novel MTC products, the application scope has increased from low- and medium-scale buildings to higher structures. However, broad adoption in Australia remains a challenge. An integrated framework might assist in overcoming obstacles in Australia. Figure 9 illustrates the major enablers for broad MTC adoption in Australia. The graphic describes the important enablers (green boxes) for each MTC phase, as well as major process stages (blue boxes) and phasing milestones (red boxes). To gain client trust and confidence in MTC, the awareness of the MTC products, and suitability to apply MTC in different project scales, sustainability benefits concerning aesthetic design, short project duration, and GHG savings are vital and vital enablers. In addition, institutional support concerning public liability insurance and financial support would also work as critical enablers to penetrate MTC in the mass market in Australia.
Moreover, regulatory policy reform is also needed, particularly around MTC products standards and specifications, and integration into the Australian National Building Codes. More importantly, ensuring that local suppliers and manufacturers of MTC productions are suitable for the Australian context is urgently needed, as is creating skilled labour. Therefore, for the widespread application of MTC, the clients’ benefits, with appropriate financial and regulatory policy support, along with local supply chains and skilled labour, need to be ensured.
Most importantly, widespread adoption of mass timber construction would best be approached from a top-down training and continuing professional development (CPD), and bottom-up education and training approach. Many highly experienced and seasoned practitioners and construction professionals are in positions to make key decisions in this space and negotiate with clients, contractors, subcontractors, and insurance companies. They are equally critical in the conversancy formula where such construction methods, contractual implications, performance, and limitations must be understood. Equally, educators teaching at the grassroots level in design and construction must also be conversant with and competent in their knowledge of MTC design and construction, their ability to teach, and their teaching pedagogical models. The study would have benefited from incorporating academics in the interviews, which is one of the limitations. As a pilot study, it attempted to understand the scope and sentiment regarding MTC and MTCPs. This study reported on the initial findings and recommendations for future study.
4. Conclusions
While there are numerous advantages to implementing MTC in Australia, such as innovative and aesthetic design, supporting forestry, and using renewable and low carbon materials, and so on, a lack of knowledge and skills is a significant barrier, contrasting with Europe and North America. The lack of local manufacturers and suppliers, leading to a longer lead time in the supply chain, is another notable challenge to the widespread application of MTC in Australia. Regarding the scale and scope of the MTC project, the study found that low- to mid-rise structures (five storey or less) were identified as the most suitable MTC projects in Australia. The demand for a shift from traditional building techniques to MTC is greatly problematic, because upfront capital costs will drive most clients. The suitable project cost of the MTC projects varied from small (less than AUD 2 Million) to large scale (over AUD 30 Million), depending on the type of the projects (residential, commercial, or public construction).
Most respondents agreed that government assistance and mainstreaming public liability insurance for MTC projects is crucial to overcoming these challenges. Moreover, industry education is critical to generating stakeholder confidence and moving forward as a collective. The investigation focused on in the perceptions analysis of widespread application of MTC in Australia from an industry context. Thus, the findings of the study would provide a good understanding for identifying the possible MTC projects in Australia from an industry context rather than an academic context. The authors acknowledge the limitations of the findings. One of the study’s limitations was that most participants had no prior MTC work experience in Australia. MTC is relatively new to Australia, and few projects have been completed here. Future research will examine the cost–benefits and life cycle environmental assessment of MTC against conventional construction.
Conceptualization, A.Z. and Y.-Q.C.; methodology, A.Z.; validation, formal analysis, A.Z., Y.-Q.C. and E.J.; writing—original draft preparation, A.Z., Y.-Q.C., E.J. and I.S.; writing—review and editing, A.Z., E.J. and I.S. All authors have read and agreed to the published version of the manuscript.
The data presented in this study are available on request from the corresponding author.
The authors would like to thank four anonymous reviewers for their feedback in reviewing and providing valuable feedback to improve the quality of the article. In addition, the authors want to thank all survey and interview participants for their time and feedback.
The authors declare no conflict of interest.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Enlarge this image.Figure 3. The reported benefits of MTC projects over the traditional construction projects.
Enlarge this image.Figure 8. Opportunities, strengths, and competitive advantages of MTC in the Australian Market.
Types of mass timber building systems.
| Timber Building Systems | Description | Common Timber Products | References |
|---|---|---|---|
| Mass timber floor and wall systems or panel systems | CLT, NLT, GLT, LSL, and LVL panels are commonly used mass timber products as floor, decking, wall, and panel systems. CLT panels have multiple layers of wood glued under pressure, with parallel boards in each layer in a different direction, usually coming in 3,5,7, and 9 layers | Cross-laminated timber (CLT), nail-laminated timber (NLT), glued laminated timber (GLT), laminated strand lumber (LSL) and laminated veneer lumber (LVL), dowel-laminated timber (DLT). | Lehmann [ |
| Hybrid mass timber systems | It includes the combination of concrete foundation and various mass timber products as core building elements and metal connectors. | Wood–concrete composite (WCC) | Boyle [ |
| Post-and-beam systems | It builds without load-bearing walls, and it is a skeleton frame composed of decking, beams, and posts. Glulam (GL), PSL/SCL, and LVL/SCL are commonly used as post and beam systems. | GL, PSL (SCL), LVL (SCL) | Boyle [ |
| Post-and-plate systems | Post-and-plate systems refer to the structural system using only columns to support the decking system. | Post-and-plate system or point-supported. | Tall-wood [ |
Respondents’ demographic data.
| Indicators | Parameters | In Percent | Count |
|---|---|---|---|
| Affiliation (N = 38) | Builder/developer | 38% | 16 |
| Contractor/subcontractor | 14% | 6 | |
| Consultant | 36% | 15 | |
| Other: | 12% | 5 | |
| Role (N = 38) | Builder | 17% | 7 |
| Architect/designer | 17% | 7 | |
| Engineer | 14% | 6 | |
| Project personnel | 29% | 12 | |
| Other | 24% | 10 | |
| Company size (N = 38) | Small (<5 employees) | 21% | 8 |
| Medium (5–50 employees) | 32% | 12 | |
| Large (>50 employees) | 47% | 18 | |
| Average years of experience project (N = 38) | 1–5 years | 29% | 11 |
| 5–10 years | 16% | 6 | |
| 10–20 years | 21% | 8 | |
| 20 years or above | 34% | 13 |
Background of the interviewees.
| Expert/Interviewees | Role/Affiliation | Company Size/No. of |
Years of |
|---|---|---|---|
| Interviewee 1 | Managing director, engineering consulting firm | 5–20 | 25 |
| Interviewee 2 | Senior structural engineer, engineering consulting firm | Above 100 | 8 |
| Interviewee 3 | Structural engineer, engineering consulting firm | 100+ | 14 |
| Interviewee 4 | Principal of research and development, |
50–100 | 20 |
| Interviewee 5 | Technical sales and engineer, mtc manufacturer | 50–100 | 7 |
| Interviewee 6 | Design coordinator, builder | 100+ | 2 |
| Interviewee 7 | Director, construction, engineering, quantity surveying, chartered surveying, building surveying, and building services engineers working with MTC | 100+ | 25 |
| Interviewee 8 | CEO, industry-funded association representing all segments of the timber industry, from forestry and manufacturing to supply | 5 | 38 |
Technical and performance limitations for MTC.
| Field | Mean | Std Deviation |
|---|---|---|
| Limited loading capacity | 3.08 | 0.84 |
| Limited size of the panels | 2.84 | 0.90 |
| Challenges of connection/joint | 3.22 | 0.79 |
| Lack of fire resistance | 3.00 | 1.05 |
| Lack of structural integrity | 3.49 | 1.00 |
| Rotting issues | 3.13 | 1.03 |
| Internal vs. external applications; interoperability with other systems | 2.95 | 0.89 |
Main barriers to widespread acceptance of MTC.
| Field | Mean | Std Deviation |
| Lack of local manufacturers | 3.03 | 0.74 |
| Lack of local suppliers | 3.03 | 0.78 |
| Lack of financial support | 3.11 | 0.88 |
| Public liability insurance | 3.22 | 1.03 |
| Long lead times | 2.95 | 0.89 |
| Current legislation with strict combustibility requirements | 2.82 | 1.00 |
| Lack of demand/market | 2.61 | 1.04 |
| Unskilled labour | 2.71 | 1.02 |
| Higher project/maintenance cost | 2.74 | 1.12 |
| Insufficient knowledge and technical information on MTC | 2.89 | 0.88 |
| Wrong ideas about the performance of MTC products | 2.79 | 0.95 |
| Durability and quality of materials (fire resistance, noise, moisture, etc.) | 2.37 | 1.04 |
| Level of market share and marketing of more traditional materials than MTC | 2.63 | 0.98 |
| Lack of regulatory requirements, including building codes/standards/specifications | 2.82 | 0.88 |
| Other | 3.33 | 0.47 |
Appendix A
Selected mass timber projects around the world.
| Project Name and Location | Completion Year | Project Type and Space Use | Project Cost | Project |
Project Size (m² or ft²) | Reported Benefits and Motivation | Number of Storey/Heights | Timber |
|---|---|---|---|---|---|---|---|---|
| Forte, Melbourne, Australia | 2013 | Residential building with multifunctional ground floor | AUD 11 Million | 10 months | - | 5-star energy rating, |
10 storeys (32 m) | 759 CLT panels (485 tonnes of timber), honeycomb construction on top of a concrete frame with a rain screen façade system |
| Library at the Dock, Melbourne, Australia | 2014 | Public building-library with exhibition and café | AUD 26 Million (AUD 8666/m2) | 60 days (timber frame) | 3000 m² | 6-star Green Star Rating | 3 storeys (10 m) | Glulam beam and columns with CLT floor panels and recycled hardwood |
| Aveo Bella Vista, Sydney, Australia | 2017 | Mixed-use building with a waterfront bistro, wellness centre and aged care residence | AUD 75 Million (AUD 12,500/m2) | 160 days timber works | 60,000 m² | Only 160 days for timber works (timber tower construction work, 86 days, and timber installation work, 74 days) | 10 storeys |
4156 CLT panels (3000 m3) used in shear walls, Glulam beams and structural steel column |
| The Incubator at Macquarie University, NSW, Australia | 2018 | Academic building | AUD 8 Million (AUD 8394/m2) | 12 months (erected in 37 days) | 953 m² | 60% less energy and heating requirements | single storey |
CLT, Glulam, Victoria Iron Ash, Australian hardwood and pine LVL |
| La Trobe University Student Accommodation, Melbourne, Australia | 2020 | Student accommodation | AUD 100 Million (AUD 160k/bed) | 18 months | 624 beds | 5-star Green Star Rating, 2 6-storey arch-shaped buildings | 6 storeys (20 m) | 4500 m3 CLT panels and GLT columns |
| Daramu House, Sydney, Australia | 2019 | Mixed-use building with commercial space (10,000 m2) and retail space (680 m2) | - | 10,680 m2 | 6-star Green Star Design and As-Built Green Star Rating, |
7 storeys (30 m) | 2290 m³ glued laminated timber | |
| 25 King Street, Brisbane, Australia | 2018 | Office building | - | 8 days of timber works and 15 months | 14,921 m2 | 6-star Design and As-Built Green Star rating, |
10 storeys |
6 m × 8 m timber grid, CLT walls, roof, and floor plates in European spruce, supported by glulam columns and beams in European spruce, with the addition of supplementary glulam beams reinforced with European hardwood LVL. Construction duration was only 20% compared to steel and concrete buildings |
| Macquarie University Clinical Education Building, Sydney, Australia | 2020 | Academic building | - | 7 months | 3325 m2 | Approximately 700 tonnes of timber structure will save the carbon emission equivalent of 5 to 6 years of energy consumption during operation 28 kW array offsets approximately 10–20% of annual energy use | 4 storeys | Cross-laminated timber (CLT) walls, and CLT floors supported by a 2.4 m by 15 m grid of glued laminated timber (glulam) columns and beams |
| Dalston Works, London, UK | 2017 | Residential building-affordable home | - | 130 weeks | 155,000 ft² (14,420 m2) | 80% less onsite construction duration |
10 storeys |
CLT panels (136,000 cubic feet), 121-unit development is made entirely of CLT, from the external, party, and core walls, through to the floors and stairs |
| Stadthaus, London, UK | 2009 | Residential building-affordable home | GBP 1420/ft2 | 9 weeks for timber structure (by 4 carpenters) | 2890 m² | 310 tonnes of carbon saving, 15% cost saving |
9 storeys (30 m) | CLT panels, honeycomb and centralised wooden elevator and stair cores |
| West Buckland School, Barnstaple, Devon | 2010 | Academic building | GBP 4.8 Million (GBP 3428/m2) | 12 months (erected in 37 days) | 1400 m² | CO2 emissions: 8 kg/m2/yr | 2 storeys (6.4 m) | Glulam beams and CLT panels |
| Tamedia, Zurich, Switzerland | 2013 | Commercial office building-headquarters and radio studios for the Swiss media company Tamedia | EUR 40 Million | 4 months for a wooden structure | 8900 m² | The cost was around 20% higher than the traditional concrete construction | 7 storeys (20 m) | Glulam beams and columns with CLT floor plates (2000 m3 of spruce wood) |
| Stadtwerke Lubeck HQ, Lubeck, Germany | 2014 | Commercial office building | EUR 17.5 Million | - | 13,856 m² | A total of 2438 m³ of timber was used in the construction from PEFC-certified suppliers | 4 storeys (12 m) | Glulam beams and columns with CLT floors and walls |
| Mjøstårnet, Brumunddal, Norway | 2019 | Mixed-use building | - | - | 11,000 m² | 4 storeys at a time in 5 construction stages | 18 storeys (85.4 m) | CLT elevator shaft, Glulam columns and beams |
| Treet, Bergen, Norway | 2019 | Multi-storey residential | - | - | 3780 m² | Built as a passive house and with universal design | 14 storeys |
Glulam trusses and prefabricated building modules, laminated timber framework. The stacking of modules is divided in phases: 4 + powerfloor (platform) + 4 + powerfloor (platform) + 4 |
| Museum of Fine Arts Houston, Houston, TX, USA | 2018 | Public building | - | - | 39,000 ft² | High-quality daylight | 3 storeys (12 m) | DLT roof panels supported with Glulam post, CNC, beam substructure, and steel connections |
| Carbon 12, Portland, OR, USA | 2018 | Residential | - | - | 3902 m² | Equipped to handle an earthquake or other natural disaster |
8 storeys (26 m) | Glulam post and beams and CLT floors and roof with a still core |
| The Soto, San Antnio, TX, USA | 2019 | Commercial | - | - | 120,000 ft² | Reduced cost LEED certification | 6 storeys (45 m) | DLT panels for floors and roof decks, supported by Glulam beam and column (20’ × 30’ grid), 1 storey of concrete with full-depth brick façade |
| T3 Atlanta, Atlanta, GA, USA | 2019 | Industrial warehouse | - | - | 205,000 ft² | LEED® certification | 7 storeys (45 m) | DLT floor and roof panels over Glulam post and beam substructure with a steel brace frame lateral system |
| 111 East Grand Office, Des Moines, IA, USA | 2019 | Commercial | - | - | 76,000 ft² | 1180 m3 of timber |
4 storeys (45 m) | Spruce glulam beams and columns frame the 40′–0″ × 6′–8″ DLT panels with pre-cast concrete walls and a core lateral system. The project applied integrated project delivery (IPD) approach with virtual design and construction (VDC) |
| Kajstaden Tall Timber Building, Västerås, Sweden | 2019 | Residential | - | - | 2400 m² | Total carbon dioxide saving is estimated to be 550 tonnes of CO2 |
9 storeys (30 m) | CLT panels, flooring, and walls |
| Sara Cultural Centre (Sara Kulturhus), Skellefteå, Sweden | 2021 | Mixed-use building | - | - | 30,000 m² | 431,000-cubic-feet of wood store about 6000 tons of carbon dioxideCarbon-negative design | 20 storeys (75 m) | CLT panels with glulam columns and beams, steel structure. The 20-storey tower is made up of prefabricated timber modules with a core of cross-laminated timber |
| NMIT Arts and Media Building, Nelson, New Zealand | 2010 | Public building | NZD 5.3 m (NZD 2676/m2) | - | 1980 m2 | 4% higher than a concrete structure |
3 storeys (10 m) | Innovative timber technology and seismic design. Post-tensioned LVL shear walls, LVL gravity frames, and timber floors. LVL-coupled shear walls for seismic layer bracing |
| Wynn Williams House, Christchurch, New Zealand | 2015 | Commercial building for office space (cost of $15 m) | NZD 15 m (NZD 2500/m2) | - | 6000 m² | Reduced cost of $2500 per m2, significantly less than published rates of $2700–$3000 per m2 for the Christchurch office building | 6 storeys (20 m) | Posttensioned LVL beams connected with posttensioned concrete columns |
| Miyamura Veterinary Clinic, Tokyo, Japan | 2015 | Hospital building- animal hospital with hospitalisation facilities | 8 months | 250 m² | 100% wood structure with high fire resistance up to 1hr (Tokyo’s required regulation is 45 min) Optimal thermal and acoustic performance | 3 storeys (10 m?) | Traditional post-and-beam wooden structure and LVL | |
| Wohnhochhaus (WoHo), Berlin, Germany | Proposed- 2024 | Residential building | 18,000 m² | Carbon neutral |
29 storeys (98 m) | CLT floor, glulam column with a reinforced concrete core | ||
| W350, Tokyo, Japan | Proposed-2041 | Mixed-use building with a hotel, residential units, and commercial spaces | GBP 4.2 b | 455,000 m² | 185,000 m3 of timber |
70 storeys (350 m) | 90% of the hybrid braced tube structure using LVL beams, columns, and diagonal steel braces |
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Details
; Ying-Qi, Chan 1 ; Jonescu, Emil 2
; Stewart, Iain 3 1 School of Design and the Built Environment, Curtin University, Perth, WA 6102, Australia
2 Hames Sharley, Level 3, 712 Hay Street Mall, Perth, WA 6000, Australia
3 Hames Sharley, Level 7, 46 Market Street, Sydney, NSW 2000, Australia