Examining the role of concrete 3D printing for housing construction on Indigenous Reserves in Canada

Abstract

Purpose

This research explores the role of concrete 3D printing (C3DP) in the development of culturally appropriate housing in Indigenous Reserves in Canada through the design, building and evaluation of the Star Lodge project located in the Siksika Nation of Alberta, Canada. The project aims to assess the potential of C3DP in addressing the escalating housing demands in Indigenous communities in Canada.

Design/methodology/approach

The research involved a collaborative and multidisciplinary approach, engaging Blackfoot Elders, Knowledge Keepers from the Siksika Nation, Siksika Housing and Nidus3D. Central to this was the design, build and documentation of the Star Lodge project to analyse the advantages and challenges, guided by weekly meetings and site visits.

Findings

The project harnessed C3DP to streamline construction, enhance durability, reduce maintenance costs and enhance the energy performance of the homes. Notable time savings were achieved compared to conventional construction methods. Challenges included developing strategies to overcome extreme cold weather conditions, achieving a consistent concrete mix and integrating conventional construction elements such as drywall construction in interiors. The project served as a platform for collaboration and community participation, shaping the design and construction process while raising awareness of innovative construction techniques in the community.

Originality/value

This study provides an evidence-based framework for the evaluation of C3DP technology by analysing the Star Lodge Project, the first C3DP project in Alberta and the largest of its kind in Canada. By addressing housing challenges in Indigenous communities, the research holds broader implications for sustainable development and Indigenous empowerment across Canada.

Citation

Soto Rubio, M., Mirza, M.F., Kagdi, M. and Bisati, A.A. (2024), "Examining the role of concrete 3D printing for housing construction on Indigenous Reserves in Canada", Frontiers in Engineering and Built Environment, Vol. 4 No. 4, pp. 285-301. https://doi.org/10.1108/FEBE-05-2024-0015

Introduction

Concrete 3D printing (C3DP) represents a promising technology with the potential to revolutionize housing construction, particularly in addressing the severe housing crisis faced by Indigenous communities across Canada. This research delves into the role of C3DP in advancing housing solutions on Indigenous reservations, focusing on the collaborative “Kakatoosoyiists” or Star Lodges project developed in partnership with the Siksika Nation housing in Southern Alberta.

The housing crisis in Indigenous communities across Canada has persisted for generations, with official reports consistently highlighting substandard living conditions, overcrowding and inadequate access to essential services (National Collaborating Centre for Aboriginal Health, 2021). In Siksika Nation, as in many Indigenous communities, the housing shortage is particularly acute, exacerbated by rapid population growth and environmental challenges such as the 2013 flooding of the Bow River, which damaged hundreds of homes on the reserve (Government of Alberta, 2023; National Collaborating Centre for Aboriginal Health, 2021). Against this backdrop, the Star Lodges project emerged as a collaborative endeavour aimed at addressing the pressing needs of the Siksika Nation community and represents a pioneering effort to leverage innovative construction technologies to provide culturally appropriate and sustainable housing solutions.

Central to the success of the project was the collaborative approach taken, which involved close collaboration with Blackfoot Elders, Knowledge Keepers, Siksika Housing and Nidus3D, a company specializing in C3DP technology. Community engagement also played a pivotal role in guiding the design and construction process, ensuring alignment with Indigenous values and traditions. Despite significant challenges associated with tight time constraints and winter construction, the project represents a testament to the resilience and determination of the Siksika Nation and its partners. By combining cutting-edge technology with traditional knowledge and community engagement, the Star Lodges project offers a beacon of hope for addressing the housing crisis in Indigenous communities and promoting self-determination in housing initiatives.

Research objectives

The core objective of this research is to evaluate C3DP technology against an evidence-based framework and determine its capacity to provide meaningful solutions to the housing crisis on Indigenous Reserves in Canada. The following five research objectives were identified:

1. To assess the viability of C3DP as a solution to streamline house construction and address the significant demand for adequate housing in Indigenous communities.

2. To investigate how the implementation of C3DP can enhance the durability of on-reserve Indigenous housing, considering factors such as climate resilience, structural integrity and long-term maintenance requirements specific to the context of Siksika Nation.

3. To evaluate the potential of C3DP to improve the energy performance of on-reserve Indigenous housing in challenging climatic environments, with a focus on reducing operational costs and promoting sustainability.

4. To examine the effectiveness and feasibility of C3DP in Canadian winter conditions and its effectiveness in overcoming seasonal changes, such as drastic temperature fluctuations.

5. To explore the capacity of C3DP to empower Indigenous communities in designing and building their own homes, thereby promoting self-determination and cultural sovereignty in housing initiatives, while also fostering community resilience and pride.

Research methodology

This research project emerged from a collaborative partnership between Siksika Housing and the School of Architecture, Planning and Landscape at the University of Calgary to address the existing crisis of on-reserve housing in Siksika Nation. The project was initiated within the framework of a Senior Research Design Studio called “Nookoowayi” (my home), which provided a platform for senior master’s in architecture students to explore innovative ideas for housing solutions. Under the guidance of (Author’s name), students engaged in collaborative discussions with Elders, Knowledge Keepers and community members from Siksika Nation to develop culturally appropriate and sustainable design concepts. The ideas generated during the studio were informed by traditional Blackfoot family structures and cultural values and included prefabrication, modular housing, incremental housing, C3DP and other emerging construction technologies. Following the conclusion of the design exercise, the researchers continued to explore the potential of C3DP as a viable option to develop housing solutions. A grant proposal was developed by Siksika Housing and submitted to Indigenous Service Canada (ISC), outlining the objectives and scope of the proposed project. Upon approval of the grant proposal, the Star Lodges project was initiated, marking the first C3DP project of its kind in Alberta and the largest in Canada.

The methodology of this research project revolves around the design, fabrication, supervision and evaluation of the Start Lodges C3DP project. It is characterized by a collaborative and multidisciplinary approach, involving close engagement with community members, engineers, contractors and other consultants throughout all stages of the project. The initial conceptual design meetings included discussions guided by the principles of cultural sensitivity, sustainability and community engagement. Researchers conducted site analysis and design meetings and developed all architectural drawings, incorporating feedback and insights gathered from community participation events and collaborative design meetings. The design priorities included functionality, durability, energy efficiency as well as practical limitations established by contractors. Throughout the construction phase, the authors maintained their involvement in the project, providing guidance and technical support and ensuring the successful implementation of the design. This involved regular site visits, inspections and coordination meetings. The methodology also included comprehensive documentation of all factors and challenges faced during the completion of the project, ranging from logistical hurdles to technical complexities associated with C3DP under extreme winter conditions. This documentation serves to capture the iterative nature of the project, highlighting both successes, challenges and lessons learnt for future implementation of C3DP technology in Indigenous housing initiatives.

Indigenous housing crisis

Indigenous housing in Canada has been in crisis for generations. Since its initial conception in 1946, official reports from the Canada Mortgage and Housing Corporation (CMHC) have consistently described the status of Aboriginal housing in Canada as substandard, unsafe, overcrowded and having insufficient access to essential services. In one of its last reports, the CMHC states that 33% of Aboriginal people living on reserve are “living below adequacy and suitability standards and unable to access acceptable housing” (Canada Mortgage and Housing Corporation, 2014). This situation is inconsistent with the standards of a developed country in the 21st century, as it drastically undermines the health, prosperity, well-being and socioeconomic interests of the indigenous community at large. The lack of adequate and dignified housing is considered a key factor regarding the broad socioeconomic crisis of indigenous peoples in Canada. Studies have shown that having an appropriate home is a crucial element for the formation of the individual and for creating a spiritual sense of belonging (Government of Alberta, 2023; Belanger, 2010; Christensen, 2016; Hill, 2010; Memmott and Chambers, 2008; Olsen, 2016). In addition, common deficiencies in indigenous housing, such as lack of ventilation, inadequate insulation and vapour barriers, have increased the community’s exposure to airborne agents, which has led to disproportionate numbers of prevalent respiratory conditions in indigenous communities (The Standing Senate Committee on Aboriginal Peoples, 2013).

Housing crisis in Siksika Nation

The condition of on-reserve housing in Siksika Nation closely follows the national trend. In January 2023, Siksika Housing, an internal government branch dedicated to the construction, maintenance and administration of all housing inside the nation (Siksika Nation, 2023), published their Short-Term Housing Strategy assessing their current housing stock and outlining their current and future housing needs (Urban Systems, 2023). According to this report, existing on-reserve housing is inadequate in quantity, due in part to the rapidly increasing Blackfoot population. Out of approximately 1,200 houses inventoried for the report, 400 units required major renovations and 200 units must be replaced entirely. The critical condition of housing in Siksika Nation was exacerbated in part by the 2013 flooding of the Bow River that damaged hundreds of homes on the reserve (Rieti, 2013). As part of the recovery work, New Temporary Neighbourhoods (NTNs) composed mainly of construction-site-like trailers were set up by the provincial government as a stop-gap measure to temporarily shelter displaced families. 10 years later, the deteriorating condition of these units poses increasing and unsustainable safety, health, maintenance and financial risks to the nation (Urban Systems, 2023). With a current total population of 7,800 and an on-reserve population of approximately 4,000 (siksikahousing.com, n.d.), the number of people living on-reserve is expected to increase by approximately 1,500 individuals over the next 20 years (Urban Systems, 2023). When a household size of four individuals per household is assumed, 375 new housing units are required over the next 20 years to address this growing demand. When people on current and projected waiting lists are considered, the number of required housing units (single-family homes and/or multi-family units) increases to nearly 1,000 units (Urban Systems, 2023). Table 1 presents the different types of housing units required on a five-year interval:

Concrete 3D printing construction

Concrete 3D printing (C3DP) is an emerging construction technology in the AEC industry that utilizes large-scale 3D printers to create entire buildings layer by layer. The technology combines computer-aided design (CAD) software, robotic arms or gantries and specialized concrete mixtures. The construction process typically entails the development of a detailed digital 3D model of the building using CAD software. The model is then sliced into horizontal layers, which serve as instructions for the 3D printer. A large-scale 3D printer is then set up on-site, typically using a gantry system or robotic arm equipped with a nozzle or extrusion system that deposits the concrete material according to design specifications.

Typical C3DP process

The concrete mixture is optimized for the printer and often includes additives or fibres to enhance its strength, durability and workability. Some mixtures also have rapid-setting properties to allow for faster construction. Depending on the design and engineering requirements, additional structural elements such as steel reinforcement bars (rebar) may be manually placed within the printed layers for added strength and stability. Once all walls are printed, all windows, doors, electrical wiring, plumbing and insulation can be installed. These finishing touches are typically done manually. The roof system in this type of construction is typically built using a conventional light wood framing system.

Advantages of C3DP

The automation aspect of C3DP stands in stark contrast to manual construction methods. It demonstrates the capability to operate continuously, without interruptions for concrete mixing or curing, effectively eliminating idle periods (Sobotka and Pacewicz, 2016). Moreover, 3D printing technology has the potential to reduce design time by up to 60% through task standardization and continuous process improvement (Rouhana et al., 2014; Wu et al., 2018). This rapid construction capability is particularly crucial in scenarios involving urgent housing needs, disaster responses or construction in remote locations (Schuldt et al., 2021).

The literature review and case studies reveal that there are potential benefits of 3D printing houses with concrete that are numerous and include the following:

1. Speed and efficiency: 3D printing can significantly reduce construction times compared to conventional methods. Because the process is largely automated, houses can be completed in a matter of weeks rather than months (Ferdous et al., 2019; Hořínková, 2021; Sobotka and Pacewicz, 2016). This is a critical factor that would allow Siksika Nation to address its current housing needs.

2. Cost-effective: 3D printing can reduce labour costs and minimize material waste. The precision of the printing process helps optimize material usage, reducing the amount of concrete required (Labonnote et al., 2016).

3. Design freedom: 3D printing enables complex and intricate architectural designs that may be challenging or costly to achieve with conventional construction techniques. The machine does not care if a wall is straight or curved (Becker et al., 2003; Hořínková, 2021).

4. Sustainability: 3D printing houses with concrete have the potential to be more environmentally friendly. The optimized use of materials reduces waste, and the proposed concrete mixtures incorporate recycled materials (Küppers and Dudnikov, 2020). Additionally, 3D printing can reduce transportation-related carbon emissions, as construction takes place on-site.

5. Onsite safety: C3DP reduces the need for manual labour in potentially hazardous construction environments, thereby improving safety conditions for workers.

Star Lodge project design and construction

Project brief

The brief of the Star Lodge project was to construct 16 single-bedroom units of transitional housing for the nation. The site, located one-hour drive east of Calgary, Alberta, is a semi-circular plot of land measuring 5.2 acres. Site analysis revealed site features such as electricity poles, water supply, sewage and gas pipelines, which helped in designing the site plan accordingly to save time and costs. Further, the site had undulating topography, which was levelled for a firm base for buildings, and extremely cold weather conditions during the winter, which required careful planning of winter construction strategies. The site planning was done considering the site features, and the buildings were arranged in a radial layout, forming a central open space to be used as recreation and congregation space for the residents.

Subsequently, housing design strategies were formulated based on the site analysis, project brief and housing issues and needs discussed with Siksika Elders and Siksika Housing during community engagement and Indigenous knowledge-sharing sessions. The design strategies (Supplementary Figure 1) encompassed constructing durable homes by quality control; reducing maintenance by ensuring durability and using standard sizes of doors, windows and furniture; making the construction process efficient by utilizing the advantages of speed and automation of C3DP construction; saving costs by reducing construction time and labour and avoiding formwork and developing culturally significant design by incorporating local art and design elements and through community participation.

Architectural design

The Star Lodge project consists of four buildings of 2,340 sq ft each with four units of 585 sq. ft in each building. Every 585 sq ft residential unit consists of one living + dining + kitchen area, one bedroom, one washroom, one mechanical room and one entrance closet (Figure 1). The architectural design focused on including natural lighting and views through windows, spacious volume by higher ceiling heights and thoughtful functional planning according to the use case under the guidance of the Elders (Supplementary Figure 2). Furthermore, the architectural design intended to showcase the cultural identity of the Siksika Nation Indigenous community by designing the roof resembling the form of a “Tipi” – a portable tent-like structure which was one of the primary forms of dwelling of Indigenous people of Canada (Kyser, 2012), and the front fascia of the gable roof planned to showcase artwork by local artists. The foundation design consists of linear footing with frost walls underneath the concrete slab over which the building structure and walls were 3D printed, while the partitional walls were constructed using metal stud framing drywall to house the building services and ease of maintenance. The roof consisted of a conventional timber truss framing structure cladded with metal sheathing for durability.

Design strategies used to improve the energy performance of on-reserve indigenous housing and subsequently reduce operational costs

To address the issues of durability and sustainability of the homes, design features and specifications were planned considering the construction methods and the project’s contextual and geographical factors. In response to the extremely cold weather conditions with temperatures as low as −40 °C, combined with strong winds and heavy snowfall, it was crucial to ensure weather protection strategies. The C3DP walls were designed to achieve an R-35 insulation rating, attributing to the 13-inch thickness of the wall consisting of cavity and poured insulation. The roof was designed to have an R-40 value and was finished with corrugated metal sheathing that boasts class 4 impact resistance to safeguard against hail damage and a 40-year paint guarantee as well as an ultra-high tensile substrate to reduce maintenance (Forma Steel, n.d.). A rainwater collection system was installed, directing rainwater from the roof to a collection tank located on the concrete pediment for daily use.

The window sizes were optimized for natural lighting in the interiors, thereby reducing the artificial lighting requirements. The windows consisted of a U-value (a measure of heat loss through the windowpane) of 1.64, a solar heat gain coefficient (SHGC – a measure of solar radiation admitted through the window) = 0.36 and an energy rating (ER – includes U factor, SHGC and air leakage) = 25. They featured low-energy argon glazing for durability, insulation and sustainability and impact resistance (IR) glass to increase the strength of the windowpane by 5–10 times, as recommended by the City of Calgary guidelines for homes (National Research Council Canada, 2024).

Furthermore, the floor slab of the project featured a radiant in-floor heating system that ensures uniform heat distribution and serves as a barrier against cold, reducing the heating requirements of the interiors. It also helped in keeping the temperature of the concrete slab warmer during the concrete printing and curing process. The floor slab also consisted of insulation below to maintain a warmer temperature. Additionally, the linear footing was equipped with extended insulation to prevent water seepage below the concrete floor slab.

Concrete 3D printing specifications

The project utilized a 3D printing gantry system, a structural configuration consisting of beams and slide rails that support the printhead/extruder, guiding its motion during both transit and the printing process. The distinctive advantage of such a system lies in its ability to traverse a broader range of directions and orientations, enhancing the 3D printing process (Symonenko, 2023). In the Star Lodge project, a gantry-based 3D printing approach was employed, using the international COBOD BOD2 gantry system (COBOD, n.d.), featuring 5 × 8 gantry modules and a printable area measuring 60’x39’. Table 1 shows the printer specifications that were used on-site as per COBOD and Nidus3D.

The concrete mix utilized in this research project was a proprietary mixture created by Nidus3D, employing Lafarge's “OneCem” low-carbon cement (Lafarge, 2024), with chemical additives and glass wool fibres to reduce curing time and achieve the desired workability and buildability during concrete extrusion. The concrete mix was designed to meet the industry standards for additive manufacturing (ISO/ASTM 52939:2023, 2023; Tyrer-Jones, 2023). The concrete was subject to rigorous testing on each printing day, evaluating air pressure, compression strength and slump test results, all of which conformed to industry standards CSA S304-14 (R2019) and CSA A179-14 (2019). These standards aim to create a common set of ISO/ASTM standards on additive manufacturing and in collaboration with the European Committee for Standardization (CEN) Technical Committee (Tyrer-Jones, 2023).

The C3DP walls of the Star Lodges consist of a 13-inch-thick 3D-printed concrete wall with two outer veneers each measuring 50 mm. An infill wavy layer, which enhances structural integrity, is attached to the inner veneer, and a 75 mm cavity is created, which is subsequently filled with spray insulation. These walls adhere to CSA S304-14 (R2019) specifications. The veneer, consisting of a single 50 mm layer of printed concrete, complies with CSA S304-14 (R2019) requirements. The cast columns and beams meet the standards set by CSA A179-14 (2019) and the Standards Council of Canada (2019).

Furthermore, concrete's inherent non-combustibility and slow heat transfer render additional fire protection unnecessary, ensuring structural integrity, fire compartmentation and effective heat shielding (The Concrete Centre, n.d.).

Concrete 3D printing process in Star Lodge

The construction process (Figure 2, Supplementary Figure 4) started with excavation, soil compaction, construction of reinforced cement concrete linear foundations and installation of electrical, plumbing and gas services in the floor slab. Later, the gantry 3D printer and the concrete mix batch plant were set up. In the harsh winters of Siksika Nation, where temperatures plummet to as low as −40°C, maintaining a minimum temperature of 5°C for C3DP construction was essential. To achieve this, a temporary heated tent structure was deployed. After curing the concrete for the first printed structure, the tent was disassembled and relocated to the footprint of the next building, effectively operating as a mobile factory setup. Setting up the heated tent took one day, and it was heated using four propane and three butane-based systems, ensuring the temperature remained above 5°C.

The concrete mix was prepared onsite using low-carbon cement from Lafarge (2024). The concrete mixture was tested for consistency and strength using an air entrainment test to measure the air content in the concrete mix affecting the durability of the mix (Seegebrecht, n.d.), a slump test to measure the flowability of concrete (Weng et al., 2018) and compression tests to measure the compressive strength. After the preparation of the concrete mix, the printer was fed with the g-code of the sliced building information modelling (BIM) model of the Star Lodge project to print the concrete along the print toolpath. The C3DP process (Plate 1) involved printing a 13-inch-thick concrete wall (Supplementary Figure 3) by printing concrete layer by layer. The C3DP wall was reinforced using reinforcement stirrups that were added along the length and height of the wall 500 mm and 480 mm, respectively, for lateral stability of the printed wall. Additionally, vertical rebars were placed for concrete casting at every 7th wave pattern, which is tied to the floor slab and the bond beam above the lintel; these vertical reinforced concrete fills functioned as columns. The bond beam functioned as a load distributor from the roof to the floor walls and to the floor through the columns.

The lintels of the window and doors were 0.5-inch-thick mild steel plates spanning across the window opening, and the concrete layers above the window were printed on top of the lintel. Close to the completion of the C3DP walls, a timber framing roofing structure was fabricated on-site and then lifted using a crane to be installed on top of the C3DP walls (Supplementary Figure 7). The roofing structure was then cladded on the top and the front fascia with corrugated metal sheeting, ensuring long-term durability. Finally, the internal walls and ceiling were constructed using metal stud drywall with a 2-h fire rating. Building services like electrical conduits, gas lines and plumbing pipes were concealed in these drywalls for ease of maintenance in the future.

The construction of one building took approximately one week, with the 3D printer operating for approximately 15 h each day, which included the pause times for placing reinforcement stirrups, electrical boxes and conduits. The time savings were possible due to the speed, autonomous nature of construction, reduced number of labourers and formwork-free concrete construction. Moreover, the precision in printing minimized material waste, while leveraging BIM and CAD optimization further contributed to material cost savings. The total project cost for four buildings, each with a 2,340 sq. ft. footprint, amounted to 2.6 m Canadian dollars. This encompassed various aspects, including design, engineering, mobilization, C3DP, doors and windows, roofing, building services and interior finishes. The heated tent costs varied with the change in temperatures, significantly increasing the total project costs.

Analysis – a manual for C3DP housing construction on Indigenous Reserves in Canada

As the project unfolded, several advantages and challenges emerged, offering valuable insights for future endeavours in the field. The crucial areas identified at the start of the project durability, sustainability, maintenance, costing, construction process efficiency and cultural significance, were analysed (shown in Table 2) by team meetings, site visits and inspections throughout the design and construction process.

Durability analysis

The successes of the project include the structural integrity of the walls, as rigorous testing confirmed the C3DP walls surpassed industry standards with 52 MPa of compression capacity and promised long-lasting housing solutions. In addition, the technology allowed for the implementation of meticulously designed insulation measures that achieve high R-values for walls (R-35) and ceilings (R-40), ensuring energy-efficient homes. The integration of drywall construction with C3DP walls was challenging at the junctions where the C3DP wall surface was not printed smoothly, causing issues in installing windows and doors, which could potentially lead to extra gaps that required covering and sealing. This was a learning curve for the designers and the contractors. Furthermore, building specifications were designed and construction quality was checked on-site to ensure healthy indoor air quality. This was done by using sufficient insulation, ensuring adequate joineries, avoiding thermal bridges and optimizing the indoor heating systems. Finally, using 2-h fire-rated drywall ensured fire safety, and the use of sturdy materials on the building envelope ensured durability.

Sustainability analysis

In terms of sustainability, the integration of rainwater harvesting acted as a strategy to save water, designing large-size windows helped in maximizing the use of natural light, and the use of adequate insulation in walls, roofing and foundations ensured healthy indoor air quality management, which enhanced the environmental sustainability of the buildings. As observed from previous studies, the life cycle assessment of C3DP was found to have a lower carbon footprint than conventional concrete construction (Abdalla et al., 2021). This included energy consumption and several factors such as material production, transportation, formwork and printing equipment.

Weather protection analysis

The weather protection for the buildings was achieved by designing a durable exterior with R-30 insulation value. The robust nature of concrete as a material and the coating of concrete sealer on the exterior ensured reduced maintenance. The span and the overhangs of the roof structure equipped with high-durability metal cladding were optimized to shelter the entrance and windows from getting damaged from direct rain, snow and hailstorms.

However, operating C3DP in extreme winter conditions posed challenges to the machinery's smooth functioning. Some hardware challenges encountered in the project included the freezing of the water measuring sensor in the batch plant and issues with the motors responsible for mixing concrete and running the extruder. Procuring spare parts for these components involved ordering from Europe, resulting in delays and budget overruns, which highlights the importance of comprehensive planning and risk management in C3DP projects, and therefore a backup stock of parts is recommended while printing in extreme weather conditions. Further, to prevent frosting inside the walls, a water stopper was used along the edges of the walls.

Therefore, it can be inferred that it is ideal to carry out C3DP construction in summer to fulfil the minimum temperature requirement of more than 5 °C. Alternatively, for smooth functioning of C3DP construction in winter, heated tent systems must be planned, spare parts must be kept as backup and cleaning of the pipes and motors after every use must be ensured.

Construction process efficiency analysis

Despite the fact that the construction process was significantly affected by the challenges related to winter temperatures, the design and construction process was relatively faster than conventional timber framing or concrete construction, which typically takes seven months in Calgary, Alberta, Canada (CMHC, 2022). However, the process required careful coordination between different contractors, ensuring adequate joineries of building components to the C3DP wall. Site visits were crucial to ensuring the construction details and quality. Additionally, the cleaning of the C3DP equipment was observed to be necessary to avoid blockage in the hose and the pump due to freezing of the water content, which could potentially damage the machine. Integrating the mechanical, electrical and plumbing (MEP) services required careful planning with some installations that had to be done during the printing process. These factors added up to the construction time; however, the use of BIM allowed for instant updates to the design and building process.

Community participation

The consultation from the Siksika Nation elders and community members through weekly meetings, community engagement sessions, seminars and presentations was integral to the process of the project and established design guidelines which were aligned with Indigenous traditions. This enhanced the sense of belonging, facilitated knowledge exchange about Indigenous ways of living and introduced C3DP and emerging construction technologies. Finally, the project incorporated design features such as niches for the display of sacred bundles in bedrooms, extended poles on the roof resembling a tipi and decorated gables by local artwork to provide a sense of belonging and cultural significance to the people of the Siksika Nation.

Cost analysis

The C3DP constituted 29% of the project costs (Supplementary Figure 5), with significant expenses attributed to the MEP services and site work. A notable factor for the increase in costs was the heated tent system required for smooth construction in winter, accounting for approximately 17% of the project cost. In comparison, Supplementary Figure 6 shows the cost distribution in the case of summers where a heated tent will not be required. Additionally, the high upfront costs of the C3DP equipment and its transportation, combined with a higher cost of the concrete mix used for C3DP than conventional concrete, contributed to the costs. This trend has been observed in previous studies on C3DP (Schuldt et al., 2021).

Conclusion

The key learnings of the project included robust contingency planning and budgeting, which are essential for addressing challenges posed by extreme winter conditions in cold climates such as Southern Alberta. Considering what tools and equipment are susceptible to frost damage is critical. The environmental and financial costs associated with protecting C3DP walls from freezing temperatures might restrict the deployment of this technology to the summer months only.

Secondly, meticulous attention to detail and rigorous quality control processes are crucial for ensuring smooth construction processes and minimizing delays. This includes ensuring the team is familiar with the equipment and can adapt to the conditions of a new site without delay.

Another key learning emerged from community engagement, which can create a sense of empowerment and ownership within the community, leading to more culturally sensitive and sustainable housing solutions (Kyser, 2012). Collaborative partnerships between stakeholders, including Indigenous communities, academia and industry, are essential for driving innovation and addressing complex social challenges. The journey through this project reinforced a crucial lesson that embracing a mindset of continuous improvement and learning is vital for navigating challenges and optimizing project outcomes. Furthermore, the project's on-site construction activities, training opportunities and collaborative approach played a substantial role in community empowerment and the democratization of C3DP technology. Finally, the documented construction process provided valuable insights into the challenges and technical parameters, including material properties and printing settings, which will contribute to optimization and error avoidance in future projects.

Limitations and recommendations

While this research covers the majority of the C3DP process from design to construction, certain factors were not included. Firstly, this research shows results based on single-story house construction, and the results might be different in multistory C3DP housing. Additionally, due to the strict timeline and winter construction challenges, the geometric exploration was limited to straight walls and rounded edges. However, geometry exploration and optimization can be performed in future projects that can help harness this advantage of C3DP, along with the possibility of extending C3DP to the construction of interior partition walls as per its viability. Moreover, the C3DP in this project was limited to a gantry system, which could be cumbersome to transport and install on-site, requiring at least 3–4 people and a crane to lift the parts. As an alternative, to achieve portability and ease of setup, a robotic arm printing system can be explored for housing construction which is appropriate in size to print a building. Additionally, the material used was cement-based; however, non-cementitious materials such as geopolymers, soil and bio-based materials can be explored to offset the carbon footprint of cement production. Further, the project must be documented post-occupancy to confirm and validate the building specifications, choice of materials and construction detailing in terms of durability, energy and sustainability.

Significance

While existing research has been limited to the study of C3DP projects in moderate climates with limited documentation of challenges (COBOD, n.d.; Jagoda et al., 2020), the novelty of this research stems from the focus of C3DP for housing construction for Indigenous communities in Canada. Additionally, the project being the first in Alberta and largest in Canada constructed in extreme weather conditions also contributes to knowledge in the field of C3DP architecture.

Given the housing crisis in Indigenous communities of Canada, this research represents a meaningful contribution to alleviate the indigenous housing crisis in Canada by collecting ideas, understanding the challenges and implementing the learnings in future housing projects. It also opens the possibility of applying C3DP to non-Indigenous homes. The research highlighted the potential of leveraging cutting-edge construction technologies to significantly enhance sustainability, housing quality and construction efficiency, setting up a precedent of learnings for future housing projects. Moreover, it fostered community participation and a collaborative approach to building Indigenous housing and raised awareness about harnessing the advantages of novel construction technologies for the improvement of housing construction in a broader vision. This collaboration serves as an example that could encourage other Indigenous communities in Canada to be interested in participating and learning about emerging construction technologies and work collectively for the betterment of the housing conditions. Following the completion of the Star Lodge project, Siksika Nation intends to build 20 more C3DP homes to meet their housing needs.

Figures

Figure 1

Typical cluster plan of Star Lodge showing four residential units

Figure 2

Construction detail sectional isometric

Plate 1.

Onsite construction process. (a) Start of concrete extrusion, (b) printing wall till sill level, (c) placing stirrups during the printing process, (d) poured insulation in the cavity of C3DP wall after curing of concrete, (e) preparing formwork for casting bond beam, (f) placing reinforcement bars and concrete pour for casting beam

Table 1

Concrete 3D printer settings – as documented on site

Concrete 3D printer settings
S.No.	Factors	Values
1	Layer height	40 mm
2	Travel speed	250 mm/s
3	Lift speed	250 mm/s
4	Nozzle	50 mm
5	Print speed	100 mm/s

Source(s): Documented by the authors on site along during construction process with Nidus3D. Authors

Table 2

Summary of analysis of the viability of C3DP for Star Lodge project

Factors	Success	Failures	Inference
Durability	• C3DP walls passed all structural tests • Adequate Insulation • Fire safety was ensured • Weather protection by insulation and overhangs	• Uneven wall surface on a few corners • Few visible cracks near the lintel and wall	• C3DP has proven to be durable and accurate
Sustainability and building performance	• Adequate insulation, indoor air quality, natural lighting, heating and rainwater harvesting • No formwork required • The life cycle assessment of C3DP was found to have less carbon footprint as compared to conventional concrete construction (Abdalla et al., 2021)	• CO2 emissions from the use of heat pumps and production of cement (Abdalla et al., 2021)	• R-30 value can be achieved using C3DP however the thickness of walls is more than conventional • Low carbon concrete and similar products are being currently considered, reducing the carbon footprint
Weather	• Water stopper provided to prevent frosting • Insulation ensured to be R-30 • Use of robust materials on the building envelope • Heated tents are used to maintain temperature	• Challenge in maintaining temperature above 5°C • Damage to printer parts due to frosting	• Winter conditions can affect the construction time even with use of heated tents • Use of tent can help in winter construction, however, the volume of the tent and the costs of heating should be optimized
Maintenance	• Little to no maintenance of C3DP walls • Building services are planned in a central location concealed in a drywall for ease of access • Windows is divided into small panels to facilitate ease of future replacement	• The accurate time to measure the building maintenance factor is after occupancy	• Maintenance of C3DP walls is lesser than conventional timber construction (Mensah, 2021) • Using modular sizes of windows, doors and furniture can ease replacement • Investing in building materials, especially in building envelope for longer durability, thereby reducing maintenance
Cost	• Reduced construction time and labour • No formwork • Saving in material using calculated quantities through BIM.	• Over budget due to extensive heating requirements and damaged part replacement during winter construction	• C3DP can save the cost of formwork and labour • Winter construction can highly impact the project costs due to heating requirements
Construction process efficiency	• Streamline design to build process using BIM – g code • Avoiding formwork saved time	• unknown challenges of winter construction • Damage of machine parts due to freezing	• BIM streamlined the design-to-construction process • No formwork leads to savings in time

Source(s): Produced by the authors based on the documentation and analysis performed during the study. Authors

Supplementary material

The supplementary material for this article can be found online.