A Case-Study-Based Comparative Analysis of Using Prefabricated Structures in Industrial Buildings

Abstract

Construction costs have increased significantly since the COVID-19 pandemic due to supply chain disruption, labour shortages, and construction material price hikes. The market is increasingly demanding innovative construction methods that can save construction costs, reduce construction time, and minimise waste and carbon emission. The prefabrication system has been used for years in industrial construction, resulting in better performance in regard to structure stability, the control of wastage, and the optimisation of construction time and cost. In addition, prefabrication has had a positive contribution on resource utilisation in the construction industry. There are various types of prefabricated wall systems. However, the majority of comparative studies have focused on comparing each prefabrication wall system against the conventional construction system, while limited research has been conducted to compare different prefabrication structures. This study examined four prominent prefabricated wall systems, i.e., precast walls, tilt-up walls, prefabricated steel-frame walls, and on-site-cut steel-frame walls, to determine which one is more suitable for the construction of industrial buildings to minimise cost, time delay, and labourer utilisation on construction sites, as well as to enhance structure durability, construction efficiency, and sustainability. One primary case project and five additional projects were included in this study. For the primary case project, data were collected and analysed; for example, a subcontractor cost comparison for supply and installation was conducted, and shop drawings, construction procedures, timelines, and site photos were collected. For the additional five projects, the overall cost data were compared. The main research finding of this study is that factory-made precast walls and tilt-up wall panels require similar construction time. However, on average, tilt-up prefabrication construction can reduce the cost by around 23.55%. It was also found that prefabricated frame walls provide cost and time savings of around 39% and 10.5%, respectively. These findings can provide architects, developers, builders, suppliers, regulators, and other stakeholders with a comprehensive insight into selecting a method of wall construction that can achieve greater efficiency, cost savings, and environmental sustainability in the construction of industrial and commercial buildings.

1. Introduction and Literature Review

Since COVID-19, the world has been witnessing a boom in online shopping and infrastructure spending, and Australia is no exception. This has amplified the need for warehouses and distribution centres, logistics and transportation hubs, power and utility plants, manufacturing facilities, data centres, and multi-story car parks; hence, the construction of such buildings has been on the rise. The walls of industrial buildings can be constructed from various types of material; however, the most common types of material are concrete and cladding [1].

According to Wu et al. (2021) [2], modern commercial construction relies on the combination of skilled workforce and the right tools and technology, and construction teams have increasingly leveraged prefabricated components to streamline the construction process and deliver the functionality that project owners need. This research focuses on two different prefabrication wall systems: factory-made precast concrete walls and on-site-precast/tilt-up walls (in this paper, these walls will be referred to as “precast” and “tilt-up” walls, respectively). In addition, this paper also examines on-site-cut steel framing panels and prefabricated panels as alternatives for steel-frame walls. By examining these four types of walls, this study covers the key wall types used for industrial buildings, as, typically, concrete walls would be utilised for the load-bearing walls, while lightweight steel-framed panels are utilised for the non-load-bearing walls.

1.1. Tilt-Up Walls

Tilt-up construction is a method of on-site prefabrication construction in which fabricated concrete walls (Figure 1), columns, and other concrete supports are lifted up to function as the shell and structure of a building [3]. Tilt-up walls are built over concrete slabs, and panels can be constructed and laid with several layers. Once the concrete panels are poured and cured on site, they are lifted up with cranes; each panel will be lined up and embedded in the concrete footing [4]. Dowels in the slab are attached to adjacent panels, ensuring structural integrity.

As Aigbavboa et al. (2017) explained in their study [5], to keep the wall panels in the upright position until they are fully secured, diagonal steel braces need to be installed to fix the wall panels and connected to the building slabs (Figure 2) to provide support. These braces can be extended or retracted prior to removal to ensure the panels are plumb and aligned correctly. The braces are removed once the placement of the other structural components, such as roofing, upper-level flooring, and posts, is completed. Tilt-up wall panels are load-bearing structure elements that eliminate the need for perimeter columns and roof beams, which are needed in most precast construction projects when wall panels are non-structural elements. These kinds of column-free walls reduce construction costs and increase layout flexibility. Typical load-bearing tilt-up panels range from 150 mm to 200 mm in size, with a concrete grade of around 40 MPa.

The tilt-up construction method has been around for a long time, but it began to gain popularity in the 1980s [6] due to the several benefits it can offer. One of the main advantages of the tilt-up wall construction method is that it allows for faster construction [3]. There are a few previous studies which have examined this construction method from different perspectives. Silungwe et al. (2020) [4] conducted research to investigate the feasibility of the tilt-up construction method for commercial buildings, and they showed that the tilt-up method is faster than the conventional method due to various reasons, including the elimination of vertical formwork, which consumes a lot of time during the installation and removal process, in addition to having the door and window openings embedded in the wall before tilting it up into place. They provided two project examples from the United States and South Africa, and these projects were completed ahead of schedule due to the utilisation of the tilt-up construction method. Furthermore, faster construction can also be achieved due to the tilt-up method allowing for certain sequences of activities which can shorten the overall critical path of projects. Barron (2021) [7] also conducted research to investigate the speed of the tilt-up construction method, and it was highlighted that the number of the critical path activities can be reduced, and many activities can be carried out simultaneously, which results in shorter construction time.

Cost-effectiveness is also another advantage of the tilt-up construction method. Adel et al. (2016) [8] have conducted a comparative study to investigate the construction time and cost of the tilt-up method in comparison with precast concrete walls and cast-in-place concrete walls. Their results showed that the traditional method had the highest cost and longest construction duration, while the precast and tilt-up methods’ results were close to each other, as they had the same construction duration; however, the tilt-up method had lower cost than the precast method by around 10.3%.

Tilt-up construction is more sustainable when compared against traditional construction. As it offers faster construction [7,8], this will result in fewer labourers commuting to the construction site, which will reduce the carbon emissions resulting from labour transportation. Tilt-up construction also eliminates the need for scaffolding [5], which, in turn, can achieve huge carbon emissions savings as it avoids the need for scaffolding itself, in addition to the need for scaffolding transportation and labour transportation. Oke et al. (2017) [9] have conducted a study to investigate the sustainability benefits of the tilt-up construction method. They surveyed industry professionals, including engineers, architects, quantity surveyors, and construction managers, in South Africa and found that the major benefits of this method include minimising cost, time, and construction waste, in addition to providing easier and safer construction procedures for the workers as it reduces human error and site accidents.

1.2. Precast Concrete Walls

In comparison with “tilt-up” walls, precast walls are engineered, fabricated, and completely cured in a factory and then transported to a construction site to be erected, lifted, assembled using cranes, and placed into the position as per design documents [10]. Temporary propping is installed to secure the prefabricated panels vertically, before being removed once the permanent adjoining structures are constructed, such as the roof, posts, and floor. Precast walls can be used for partitions, façades, boundary walls, or for architectural design purposes pertaining to aesthetic and visual appeal, structural integrity and safety, sustainability, natural hazard resilience, and energy efficiency [11]. Load-bearing precast concrete panels can eliminate the need for steel columns, though precast columns, beams, flooring, and roof members need to be built. Designed with precisely specified reinforcing steel, the panels offer both structural strength and compressive durability. The thickness of a typical load-bearing precast panel is around 200 mm, and the concrete grade can as high as 80 MPa.

Precast concrete structures are well known and widely used for their vast potential to speed up the construction process and improve efficiency [12]. This is due to their ability to enable the start of the production of prefabricated construction components in the early stages of construction projects, which can generally result in significant reductions in construction time of up to 40% [13]. Weng et al. (2022) [11] conducted a study to shed light on the current status of precast concrete walls in Australia, and their study showed that industry professionals in Australia favour the precast concrete construction method due to the previously mentioned reasons, in addition to the fact that it reduces the amount of work on site, which, in turn, helps in solving the current labour shortage and reduces labour costs [11].

In regard to construction costs, they vary from one project to another, as it is perceived that the precast construction method usually comes with higher material costs, particularly in small projects [14]. However, when incorporating all the other indirect costs—such as labour costs and construction operation costs, including equipment and machinery rental and operational costs—the precast method can yield lower costs, as it significantly reduces the construction time, which, in turn, reduces the construction operation costs. Hui et al. (2020) [15] conducted a comparative study to examine the cost of precast construction against the conventional construction method. Their findings indicated that, in terms of direct material costs, the precast method was more expensive; however, when they incorporated all other factors, such as labour costs and plant rates, it appeared that the precast construction method was the more cost-effective one, and it achieved a cost saving of 16% [15].

Furthermore, sustainability is also another important factor to consider when deciding on using the precast construction method. Dong et al. (2015) [16] conducted a study to compare the carbon emissions of the precast construction method against the traditional cast-in-place concrete method throughout the life cycle of two projects in Hong Kong. Their results have shown that the precast method reduces carbon emissions by around 10%. Sandanayake et al. (2019) [17] have conducted a study to quantify the carbon emissions of precast concrete structure and compare them against those of the conventional method. They found that an 8.4% reduction in carbon emissions can be achieved by utilising precast concrete structures.

1.3. Steel-Frame Walls

The use of steel framing panels (Figure 3) is another type of exterior and interior wall construction method for industrial buildings [18]. On-site-cut and prefabricated steel framing are the two common methods of wall construction. Cold-formed light steel is widely used in commercial and industrial buildings, hotels, and residential buildings. It is supported by structural components such as heavy steel or concrete structures [19]. Cold-formed light steel is durable, light, flexible, and easy to manufacture and handle, and it also has better corrosion-, fire-, and termite-resistant properties [20,21]. In the case of on-site-cut steel framing panels, the light steel studs are delivered to the site, cut on site, and assembled to suit the specific project condition. The location and dimensions can be adjusted to allow for better customisation and more flexibility. Whereas in the case of prefabricated steel framing panels, the steel framing is designed with 3D software, cut, and assembled and manufactured in a factory; then, it is transported to the site and installed with adjacent structures at the site [22].

Lightweight steel-frame panels are usually used for non-structural partition walls and exterior façade walls [23]. Therefore, they are insufficient with respect to withstanding lateral loads on their own [24] and require other load-bearing structural elements to complement them, such as concrete columns or structural steel [19]. The lightweight steel framing construction method is preferred due to the flexibility it offers, in addition to its ease of installation, as it can be prefabricated and delivered to the site [25]. There are a few studies examining the structural performance of this construction method, yet no published study has investigated the productivity of this method in terms of its effect on the speed of construction and its cost-effectiveness.

There are several prefabrication methods, though the limited research makes it difficult to compare them against each other. Precast walls and tilt-up walls are commonly used as alternatives in the construction of industrial buildings. While there are numerous studies focused on assessing the precast wall method, there are a limited number of studies that have investigated the construction efficiency of the tilt-up wall method to compare it against other wall types. Furthermore, previous studies have generally focused on comparing prefabricated construction methods against conventional ones. Structural designers and builders can find it challenging to select the right type of construction method for each project. Therefore, this research aims to contribute to filling this research gap by conducting a comparative analysis between precast and tilt-up concrete wall panels, which are the two primary prefabrication construction alternatives for industrial buildings. This research investigates and compares the factors that can impact the wall construction method for industrial building construction, identifies the challenges for each construction method, and discusses which method is more favourable to the market. Multiple case studies in NSW, Australia, have been examined to demonstrate how a comparison can be made, however this study does not intend to generalise the results to all circumstances or geographical locations. The factors that were incorporated into the assessment are site access, construction design, construction schedule, construction cost, transportation, and wastage.

2. Research Methodology

As the primary focus of this research is to evaluate the cost-effectiveness and overall project productivity of alternative walling construction methods, a quantitative research approach was employed to analyse the collected data. A comparative analysis was carried out for two alternative concrete wall types, i.e., precast walls and tilt-up walls. In addition, comparative analysis was also conducted for two alternative wall framing construction methods, i.e., on-site-cut wall framing and prefabricated wall framing. This is because these concrete wall types and steel framing panels are used to complement each other in industrial buildings. Several completed industrial building projects were examined as case studies to compare the built-up wall types against the potential alternatives. The main case study industrial building is located in Dapto, New South Wales, Australia, and it consists of seven warehouses. This particular project was selected due to it being a typical standard industrial building without any design complexities or site access issues, as any of these complicated factors may affect the project cost and schedule.

Important aspects of the industrial buildings were thoroughly examined, including their design and construction details. A wide range of information and data were collected and analysed, including subcontractors’ tenders, material supply and installation costs, transportation costs, project schedules and critical paths, construction hours, construction sequences, timelines, site photos, and plant and equipment utilisation.

Wall measurements and quantity take-offs were carried out. Each wall quantity was multiplied by its relevant dollar rate to calculate the total cost. The critical path method (CPM) was utilised to develop the construction schedule for each wall type. This allowed for the identification of the critical tasks which would facilitate the completion of construction in a timely manner.

The cost and construction schedule of the built-up wall types were analysed and compared against the developed cost and schedule of the alternative wall types. Furthermore, additional factors, such as flexibility of design and construction, transportation, waste generation, and insulation, were also examined for each wall type by obtaining insights from industry professionals, in addition to reviewing the concepts and findings of previous studies.

3. Case Study Analysis and Discussion

A typical industrial building (Figure 4) in Dapto, approximately 100 Km south of Sydney, NSW, Australia, was taken as a case study. The building consists of a ground floor level and a mezzanine level, and it is divided into seven warehousing units. The exterior walls of the ground floor are made of concrete, and the interior walls as well as the mezzanine level exterior walls are made of frame panels. The following sections of this paper present a comparison of the alternative walls.

3.1. Concrete Wall Comparison

3.1.1. Planning of Construction Process

The fundamental difference in the sequence of activities between the two concrete walls is that precast walls are completely poured off site in a factory and delivered to the site ready for installation, which allows for precast panel production in the early stages of the construction project. However, tilt-up concrete walls are poured on site only after the completion of ground slab construction, and then, they are lifted up into place. Figure 5 and Figure 6 show the construction sequence for precast concrete walls and tilt-up walls, respectively.

As illustrated in the construction sequence (Figure 5 and Figure 6), precast wall panel production can commence as soon as the production drawings are ready, without the need to wait for site preparation to be finalised, whereas, in the case of tilt-up walls, the panels cannot be constructed until the floor slab is poured and ready.

Table 1. Precast concrete wall construction programme.

Item	Task	Starting Date	Completion Date	Duration (Working Days)	Predecessors
1	Prepare panel shop drawings	23 April
2	Demolition and excavation	8 May 2023	26 May 2023	15	1
3	Procure panel contractor	8 May 2023	2 June 2023	20	1
4	Prepare production drawing	5 June 2023	16 June 2023	10	3
5	Panel manufacturing	19 June 2024	14 July 2023	20	4
6	Piering	29 May 2023	5 June 2023	6	2
7	Slab construction	6 June 2023	7 July 2023	24	6
8	Site preparation for panel installation	10 July 2023	14 July 2023	5	7
9	Panel transportation	17 July 2023	18 July 2023	2	5 & 8
10	Panel installation and bracing	19 July 2023	24 July 2023	4	9

and

Table 2. Tilt-up concrete wall construction programme.

Item	Task	Starting Date	Completion Date	Duration (Working Days)	Predecessors
1	Prepare panel shop drawings	23 April
2	Demolition and excavation	8 May 2023	26 May 2023	15	1
3	Procure panel contractor	8 May 2023	2 June 2023	20	1
4	Prepare Installation drawing	5 June 2023	16 June 2023	10	3
5	Piering	29 May 2023	5 June 2023	6	2
6	Slab construction	6 June 2023	7 July 2023	24	5
7	As-built survey and finalise panel shop drawings	15 June 2024	7 July 2023	17	1SS, 6SS
8	Panel construction	26 June 2023	14 July 2023	15	7SS
9	Site preparation for panel installation	17 July 2023	18 July 2023	2	8
10	Panel installation and bracing	19 July 2023	24 July 2023	4	9

show the construction programmes for the two walls, illustrating the start and completion dates of each activity.

According to the workflow and schedule for design, manufacturing, and construction, there is no significant difference in the on-site construction time between tilt-up panels and precast concrete panels. However, precast panels require a highly accurate as-built survey to ensure precision during manufacturing and installation. If there is any inaccuracy in the survey or manufacturing process, it can be challenging to make modifications on site due to the size, weight, and hardness of the concrete. In contrast, tilt-up panel construction allows for more flexibility on site, as measurements can be double-checked, and adjustments can be slightly made as required on the construction site.

3.1.2. Cost Comparison

The actual cost of the built tilt-up wall panels after completion was $308,020 (excluding GST), whereas the estimated cost of precast wall panels was around $416,943 (excluding GST). Each wall type cost is based on 240 m³ and 1600 sqm of concrete panels, each with a thickness of 150 mm. This equates to approximately $192.5/sqm (excluding GST) for the tilt-up panels and $260.5/sqm (excluding GST) for the precast panels.

Table 3. Scope of work for precast and tilt-up concrete panels.

Item	Precast Wall	Tilt-Up Wall
Structure steel	×	×
As-built survey	×	×
Panel set out marking	×	×
Concrete pads	×	×
Casting slab	×	✓
Supply electricity and water	×	×
Traffic control	×	×
Authority approval	×	×
Design coordination	✓	✓
Transportation	✓	✓
Panel thickness	150 mm	150 mm
Steel reinforcement supply and placement	✓	✓
Concrete supply and placement	✓	✓
Ferrule supply and installation	✓	✓
Dowels supply and installation	✓	✓
Bracing supply and installation (3 weeks)	✓	✓
Bracing removal	✓	✓
Crane transportation and lifting	✓	✓
Panel bond breaker	✓	✓
Sealer to panels vertically and horizontally	✓	✓
Bracing supply and installation (3 weeks)	✓	✓
On-site Waste	×	✓
Transportation Requirements	✓	✓

shows a summary of the required scope of work, and

Table 4. Cost comparison for precast and tilt-up concrete panel.

Item	Precast Wall	Tilt-Up Wall
Original Cost (Excl. GST)	$416,943	$307,000
On-site Waste (Excl. GST)	$0	$1020
Total Cost (Excl. GST)	$416,943	$308,020

shows a cost comparison for precast and tilt-up wall panels.

As presented in the table above, precast panels would cost $108,923 more than the tilt-up wall alternative. This translates to approximately 26.1% cost savings being achieved by the tilt-up method due to several factors, including the additional cost of precast panel factory overhead expenses and the higher transportation costs. The latter is attributed to the increased number of trucks required to transport the precast panels due to their size and weight. In comparison, the transportation needs for tilt-up panels are only half of that for precast panels, and the trucks used for tilt-up panels are smaller in size, around 10 and 20 tonnes, predominantly used for the delivery of formwork, steel, chemicals, and other raw materials. For instance, for this case study, the precast panels required 10 delivery trucks (25-ton flatbed truck) and 1 truck (20-ton flatbed truck) for bracing, whereas the tilt-up wall method requires 2 delivery trucks (20-ton flatbed truck) for formwork and chemical materials, 2 trucks (10-ton flat-bed) for steel and accessories, and 1 truck (20-ton flatbed truck) for bracing. Furthermore, the level of crane utilisation is also higher in the case of precast panels; as they are smaller in size, there is a greater number of panels to install, requiring more installation time, which will increase crane rental costs.

3.1.3. Other Factors

Flexibility of design and construction, transportation, waste generation, and energy efficiency should be considered in the assessment, in addition to construction time and cost.

Table 5. Additional factors for comparison of precast and tilt-up concrete walls.

Factor	Precast Wall	Tilt-Up Wall
Flexibility of design and construction	Limited flexibility due to panel size limitations. Once precast panel manufacturing commences, no alterations or modifications can be made.	Tilt-up walls are more flexible. As they are casted on site, they can be slightly adjusted to accommodate minor design changes.
Transportation	More transportation activities required due to smaller panel sizes.	Less transportation is required due to casting on site.
Construction waste generation	No waste on site.	Minimal waste on site.
Energy efficiency (insulation)	Precast panels can be separated with concrete ribs and include pockets of interrupted insulation, which air and water can infiltrate.	With fewer panel joints, tilt-up insulated concrete panels provide continuous insulation, with there being less air and water to penetrate a tilt-up wall.

presents a summary of these factors.

3.2. Steel-Frame Wall Comparison

Steel-frame walls were utilised for the interior walls of the building, as well as in some parts of the non-load-bearing mezzanine level exterior walls. The two alternative types of wall panel construction are on-site-cut and assembled light steel-frame panel construction and prefabricated Light Gauge Steel (LGS) frame panel construction. The scope of work included the design, manufacturing, delivery, installation, and certification for the internal walls on the ground floor, the internal and external walls on the mezzanine floor, and the eaves and awnings. The evaluation criteria incorporated several factors, including the construction programme, plant and equipment requirements, transportation and labour requirements, construction costs, and waste management.

3.2.1. Construction Programme

Traditional on-site panel installation does not require an as-built survey, as all measurement, cutting, and installation tasks are carried out on site. However, while this method ensures accuracy in wall panel construction, the installation process takes at least 13 working days. This is significantly longer than the time it takes to install prefabricated panels, which is only around 4 working days.

In contrast, prefabricated LGS requires an as-built survey to ensure construction accuracy. If any discrepancies are found, modifications to the frame will be made. On-site installation for prefabricated LGS takes 4 working days to complete. However, project management and task coordination, including the as-built survey, design, manufacturing, delivery, and construction, must be carefully arranged to avoid any errors. When properly managed, the project can proceed without errors or delays.

Table 6. On-site wall panel construction programme.

Item	Task	Duration	Completion Date	Duration (Days) Excluding Holidays
1	Structural Steel	25 July 2023	4 August 2023	9
2	Mezzanine Floor Slab	23 January 2024	29 March 2024	47
3	Wall Frame Delivery	2 April 2024	3 April 2024	2
4	Wall Frame Construction (External and Internal)	3 April 2024	19 April 2024	13
5	Window Installation	22 April 2024	30 April 2024	6
6	Cladding Installation	1 May 2024	24 May 2024	18

and

Table 7. Prefabricated LGS construction programme.

Item	Task	Starting Date	Completion Date	Duration (Days) Excluding Holidays
1	Structural Steel	25 July 2023	4 August 2023	9
2	Mezzanine Floor Slab	23 January 2024	29 March 2024	47
3	LGS Frame Shop Drawings	11 April 2024	11 April 2024	1
4	As-Built Survey	19 March 2024	20 March 2024	2
5	Lock Up LGS Frame Manufacturing Drawings	21 March 2024	22 March 2024	2
	Wall Frame Manufacturing	25 March 2024	29 March 2024	4
6	Wall Frame Delivery	2 April 2024	3 April 2024	2
7	LGS Wall Frame Construction	3 April 2024	8 April 2024	4
8	Cladding Preparation	4 April 2024	7 April 2024	2
9	Window Installation	9 April 2024	16 April 2024	6
10	Cladding Installation	17 April 2024	10 May 2024	17

show the construction programmes of the on-site wall panel construction method and the prefabricated LGS construction method, respectively.

As illustrated in the construction programme tables, the utilisation of the prefabricated LGS panel method reduced the construction time by 10 working days in this project, which is approximately 10.5% of the construction time, as the construction project was on hold in the period between 5 August 2023 and 22 January 2024. This time saving is not only attributed to the quick installation process offered by the prefabricated LGS panel method but also to the ability to have overlapping construction activities, which results in an earlier project completion time.

3.2.2. Cost Comparison

Prefabricated LGS panels offer substantial cost savings. The original cost for prefabricated panels is $30,141, compared to $51,000 for on-site-cut wall frames, which results in cost savings of approximately 40.9%, without consideration of on-site surveys, access equipment, and on-site waste. If these three factors are taken into consideration, the minimum saving of using prefabricated LGS panels would be around $21,370 (excl. GST), yielding a cost saving of around 39%.

Table 8. Scope of work for steel-frame wall panel construction.

Item	On-Site-Cut Wall Panel (Excl. GST)	Prefabricated LGS Panel (Excl. GST)
Design	×	✓
Manufacturing	×	✓
Supply	✓	✓
Installation	✓	✓
Certification	✓	✓
Internal wall on ground floor	✓	✓
Parti wall on mezzanine floor	✓	✓
Internal wall on mezzanine floor	✓	✓
External wall on mezzanine floor	✓	✓
Awnings and eaves	✓	✓
Material delivery	✓	✓
Access equipment	×	×
On-site waste	✓	×

presents the required scope of work, and

Table 9. Cost comparison for steel-frame wall panel construction.

Item	On-Site-Cut Wall Panel (Excl. GST)	Prefabricated LGS Panel (Excl. GST)
Original cost (Excl. GST)	$51,000	$30,141
Adjustment with on-site survey	$0	$1500
Adjustment with access equipment	$3482	$1741
Adjustment with on-site waste	$350	$80
Total cost after adjustment	$54,832	$33,462

presents the estimated cost comparison for both of the construction methods.

As shown in the table above, prefabricated LGS wall panels were found to cost less than the on-site-cut alternative. This cost saving achieved by the prefabricated wall frame construction method can be attributed to the shorter on-site installation time, which offers significant savings in labour costs, as well as equipment rental costs.

3.2.3. Workforce for Unloading and Installation

Prefabricated LGS panels can significantly reduce the required workforce and work duration. Only two workers per day are required for 4 working days, compared to four workers per day for 13 working days with on-site-cut wall frames, and the labour cost is reduced significantly. Based on an assumed salary of $75/h for each worker, the labour cost for prefabricated LGS installation is $26,400 (excluding GST), which is lower than the on-site-cutting labour cost.

Table 10. Workforce and work duration comparison for wall panel unloading and installation.

Task	Labour	Work Duration	Cost ($)
On-site-cut Wall Frame	4 persons per day	13 working days	31,200
Prefabricated LGS Panel	2 persons per day	4 working days	4800

shows a summary of labour requirements and costs.

3.2.4. Transportation and Equipment

Prefabricated panels require twice as many trucks (four delivery trucks) compared to on-site-cut wall frames (two delivery trucks). However, due to the size of the panels, both methods require similar unloading equipment, i.e., a crane arm on the delivery truck.

Both construction methods use the same access equipment (scissor lift and boom lift), but the prefabricated panels reduce the work duration and cost by half for using the scissor lift and boom lift, from $3482 to $1741 (excl. GST).

Table 11. Transportation requirements for steel-frame wall panels.

Panel Construction Method	Truck	Qty	Unloading Equipment
On-site-cut Wall Frame	Flatbed 20 ton	2 trucks	Crane arm on the truck
Prefabricated LGS Panel	Flatbed 20 ton	4 trucks

and

Table 12. Equipment requirements for steel-frame wall panels.

Panel Construction Method	Access Equipment	Work Duration	Cost ($)
On-site-cut Wall Frame	1 scissor lift and 1 boom lift	13 working days	3482
Prefabricated LGS Panel	1 scissor lift and 1 boom lift	4 working days	1741

summarise the transportation and equipment requirements for each construction method.

3.2.5. On-Site Waste Generation

It is well known that prefabricated construction methods generally reduce the generation of on-site construction waste [26]. Previous studies have found that off-site construction can reduce waste generation by around 20–65% [27]. Certainly, the same is applicable in the case of on-site-cut steel-frame walls versus prefabricated steel-frame wall panels. Therefore, it is valid to deem that the prefabricated steel-frame construction method would generate less on-site construction waste.

4. Additional Case Studies

Five additional projects in New South Wales, Australia, that were built with tilt-up walls were examined to further investigate the tilt-up walling construction method. Four of these projects were industrial buildings, and the fifth was a commercial building (a shopping centre). The examined buildings were built by three different contractors, and all of them were used to compare tilt-up walls with factory-made precast wall panels.

Table 13. Cost comparison of additional case studies.

Project	Location (NSW)	Wall Area (M2)	Construction Duration (Days)	Precast Cost ($)	Tilt-Up Cost ($)
Industrial Building (9 Units)	Taree	3500	40	875,000	700,000
Industrial Building	Unanderra	2500	35	587,500	450,000
Industrial Building	Unanderra	2200	32	517,000	396,000
Industrial Building	Unanderra	1500	30	352,500	270,000
Shopping Centre	Leppington	5000	50	1,000,000	750,000

presents a summary of the actual tilt-up construction cost for these five projects against the estimated costs for the precast alternative. The total cost of the alternative precast panels, including installation, was calculated based on a unit cost estimation of $250/sqm for the Taree project, $235/sqm for the Unanderra projects, and $200/sqm for the Leppington project. These cost data were provided by the contractors. While the factory manufacturing cost is similar, the differences in the unit price reflect the impact of transportation distance and installation cost due to the different site conditions.

It is evident that the tilt-up construction method costs less than the precast method in all five projects and tilt-up walls have been adopted.

The average cost saving of these five projects combined with the main case study project is 23.55 %. The fact that all these different contractors have unanimously chosen to build their projects with the tilt-up walling method proves that it is considered a more favourable choice. The higher transportation costs and additional overhead expenses associated with precast panel manufacturing have made precast panels a more expensive option.

Furthermore, previous research conducted by Adel et al. (2016) [8] compared the construction time and cost of precast walls and tilt-up walls. Their research concluded that precast walls and tilt-up walls have similar construction times; however, the construction cost of tilt-up walls is 10.3% lower than that of precast walls. Their finding is in line with the findings of this study.

For these five cases, data for LGS framing panels were not collected from the builders. This is because the cost of LGS framing is significantly lower compared to the costs for load-bearing tilt-up walls and precast concrete walls. As demonstrated in the primary case study, the tilt-up and precast wall costs were $308,020 and $416,943, respectively, whereas the prefabricated and on-site-cut framing panel costs were only $33,462 and $54,832, respectively. Therefore, this data will not affect the conclusions of our research.

5. Discussion and Conclusions

This study examined four distinct types of wall systems commonly used in industrial buildings. These include factory-made precast concrete walls and on-site precast and tilt-up walls, which are primarily utilised as load-bearing walls due to their high structural strength and durability. Additionally, the study analysed prefabricated LGS frame panels and on-site-cut steel-frame walls, which serve as non-load-bearing walls, offering flexibility and ease of installation.

These four wall systems are extensively used in the construction of industrial buildings, each providing specific advantages based on structural requirements and project constraints. A typical industrial building often incorporates both concrete and steel-frame walls within its design, as they can complement one another. Concrete walls offer superior load-bearing capacity and durability, while steel-frame walls provide lightweight, cost-effective solutions for partitioning and enclosure. The combination of these materials allows for an optimal balance between structural performance, cost efficiency, and construction speed.

One of the main contributions of this study is the examination of an on-site prefabrication construction method, i.e., tilt-up construction. Data were collected for one primary project and five additional projects located in New South Wales, Australia. The collected data for the primary project included architectural and structural drawings, construction schedules and costs, and data pertaining to transportation and equipment requirements. A quantitative research approach was employed to analyse the collected data, and it was found that tilt-up construction has a similar construction time to the precast method. However, it was also found that the tilt-up method offers significant transportation, handling, and installation cost savings. The cost comparison between the tilt-up wall construction method and the precast wall construction method for the five additional projects supports the findings from the primary case project, and the total average cost saving is around 23.55%. This finding is also in agreement with the research of Adel et al. (2016) [8], as they found that the tilt-up construction method had the lowest cost when compared against the traditional cast-in situ and precast methods. Furthermore, the flexibility offered by the tilt-up method is also another advantage, as precast concrete method requires more project management and team coordination, as well as logistical planning. These requirements can also increase the indirect costs. Therefore, the tilt-up construction method is a more cost-effective solution for small- to medium-sized industrial buildings.

The precast method requires detailed and complex planning, as panel production might start in the factory even before on-site construction commences. This means any mistake or change in the design can cause significant losses. The tilt-up method was found to have a lower cost as, typically, the construction process is handled by the builder, whereas in the case of the precast method, panel construction would be handled by an external factory, which comes with additional operation costs and profit margins. Additionally, precast panels are smaller in size, which results in the need for a larger number of them, which would require more transportation and crane utilisation.

Furthermore, this research has also highlighted the substantial advantages of prefabricated LGS panels in industrial building construction over traditional on-site-cut wall frames. Prefabricated panels were found to offer significant labour, time, and cost savings, reducing construction duration by 10.5% and total costs by around 39%. Additionally, prefabrication minimises on-site construction waste and environmental impact, aligning with sustainability goals. While prefabrication demands more coordination and logistical planning, these costs are offset by reduced labour needs, shorter installation timelines, and less material waste. Therefore, prefabricated LGS panels offer a highly efficient and sustainable solution for industrial building construction.

Reducing construction time not only leads to faster project completion but it also results in lower construction costs, as huge savings can be made in labour and equipment and machinery rental costs. Although the transportation cost of the prefabricated LGS method is higher than the on-site-cut frame method, the overall cost is significantly lower. In addition, the reduction of construction waste is also another significant advantage offered by the prefabricated LGS method.

This research enhances project management decision-making by equipping construction professionals with a data-driven understanding of how various walling systems impact construction timelines, workforce requirements, and overall project costs. By identifying the advantages and constraints of each system, the findings contribute to the development of more strategic planning, resource allocation, and risk mitigation approaches in construction projects.

Additionally, this study bridges the gap between theoretical knowledge and practical application, offering empirical evidence that can be utilised for cost estimation models, scheduling optimisation, and sustainability assessments. The results serve as a valuable reference for construction managers, engineers, and policymakers seeking to improve efficiency, productivity, and financial viability in industrial building projects.

One of the limitations of this study is that the examined case studies were all in Australia. Investigating the same wall alternatives in different countries can provide a clearer picture of their assessment results. Another limitation is the scarcity of published peer-reviewed academic studies that scientifically examine the tilt-up construction method with a real-life case study approach. Such studies can provide better guidance in the assessment of methodologies and definitive validation results.

Further research is urgently needed in the area of tilt-up construction. Detailed life cycle assessment studies need to be conducted to examine this construction method’s carbon footprint and compare it with that of other alternatives, such as precast and traditional cast-in situ construction methods. Future research is also required to investigate the waste generation of the tilt-up construction method, as it still requires on-site casting.