The growth of the construction sector in Indonesia is spurred by the need for public facilities and high-rise buildings, where time, cost, and quality efficiency become crucial aspects in the success of a project. Building structures, especially columns, beams, and floor plates play an important role in determining these three aspects, as explained by (Rani & Fuadi, 2016) .

Two commonly used methods are conventional concrete (cast-in-situ) and precast concrete. Conventional concrete is cast directly at the project site from formwork installation, reinforcement, casting to curing, which generally consumes a lot of time and labor, and is vulnerable to weather disturbances (Najoan et al., 2017) . In contrast, precast concrete is produced in controlled facilities such as precast yards, then transported and installed in the field offering better quality control and speed of execution.

The use of precast methods is considered more efficient in terms of speed and quality because the structural elements are produced under more controlled conditions. Precast concrete has advantages in terms of quality, productivity, and quality control because the production process is carried out in a place that is not directly affected by weather and project environmental conditions (Špak et al., 2016) . In addition, precast systems can reduce the volume of site work, including casting and concreting.

However, the precast method is often associated with higher initial costs, particularly for production, transportation, and installation. For example, a comparative study of structural systems for low-cost apartment buildings (Pakiding, 2022) found that the use of the precast method was 26% more expensive than the conventional method, but resulted in a time acceleration of approximately 21 days. In contrast, a study by (Alvandi et al., 2021) explained that the use of precast concrete for beam structures had a lower cost than conventional concrete, with a cost difference of IDR 121 million.

With the increasing need for efficiency in the construction of high-rise buildings, the selection of the right construction method is key to the success of the project. Therefore, this research is important to provide data-based input in determining the concrete structural system that best suits the characteristics of the project, not only from a technical aspect, but also in terms of cost and implementation efficiency.

This research uses a comparative quantitative approach, which is an approach that aims to compare two or more variables statistically based on numerical data obtained from the field and project documentation. This type of research focuses on hypothesis testing to determine whether there is a significant difference between two construction methods, namely precast concrete systems and conventional concrete systems, in terms of the total cost of implementing multi-storey building projects.

This research was conducted at the Sartikaasih Bhayangkara Hospital building project, Jl. BKR, Pelindung Hewan Village, Astanaanyar District, Bandung City, West Java Province.

The type of building in this project is a hospital building consisting of two main buildings: Building A1, is a multi-storey building with a total of 9 floors while Building A2, is a multi-storey building with a total of 5 floors. Both buildings are designed to support hospital operations in an integrated manner, with the division of space functions according to the needs of medical and administrative services.

Each building has a different number of floors and building area, as follows:

Table 1. Building Area of Each Floor

Building A1 is a building with a total of 9 floors, has a total area of 10,926 m² and a total building height of 35 meters. The most spacious floor is on the fourth floor which is 1,468 m² and the floor with the largest height is the first floor as high as 6.2 meters, which is designed for the lobby or main access function of the hospital.

Meanwhile, Building A2 consists of 5 floors with a total area of 8,638 m² and a total building height of 19 meters. The 6.2 meter-high first floor is designed for activities with high circulation, although the hospital's central access and public services are located in Building A1. The largest floor area is on the third floor, 2,161 m², which is used for large horizontal space requirements such as hospitalization, medical support facilities, and other operational units.

Table 2. BOQ of Precast Concrete

Based on the RAB results, the total construction cost with the precast concrete system is IDR 17.6 billion for Building A1 and IDR 12.74 billion for Building A2. The largest cost component was identified on the 3rd floor in both buildings. The characteristics of the precast system indicate a larger initial investment requirement, along with the demands of fabricating and installing the elements off-site. Nonetheless, this system provides advantages in terms of accelerated implementation time as well as improved quality control of the building structure.

Table 3. RAB of Conventional Concrete

As for the conventional concrete system, the total construction cost was recorded at Rp 19.86 billion for Building A1 and Rp 14.29 billion for Building A2. As with the precast method, the highest cost also occurred on the 3rd floor in each building. This method is more economical in terms of direct costs, but requires a longer implementation duration and has a high dependency on field activities and unpredictable weather conditions.

The results of this study are in line with the findings (Teknik et al., 2024) which concluded that the use of precast concrete systems can accelerate project execution time as well as significantly reduce labor costs. In addition, the study by (Nauly et al., 2022) also supports these results, stating that precast systems have major advantages in terms of construction time efficiency.

However, the results of this study are not entirely in line with the study conducted by (Senduk et al., 2022) , which shows that in the flats project, the precast system is indeed more economical in total than the conventional system, except for the floor slab element. This finding indicates that the cost efficiency of using precast systems may vary depending on the type of structural elements used. In particular, beam and column elements tend to be more cost-effective using precast methods.

The analysis results indicate that although the precast concrete system tends to yield lower direct construction costs compared to the conventional concrete method, its primary advantage lies in the efficiency of structural work duration. In the two case study buildings analyzed, the precast system proved to be more economical in nominal cost while also completing the structural works in a significantly shorter time than the conventional method.

Furthermore, the considerable difference in total cost and execution duration between the two construction methods provides a basis to conclude that there is a significant relationship between the construction system used and the total project efficiency. Therefore, based on the results of this analysis, it can be stated that there is a strong basis to receive the alternative hypothesis and reject the null hypothesis. This finding provides important implications in making technical decisions in the selection of construction methods, especially in multi- storey building projects, where cost effectiveness and time efficiency are the main considerations in the successful implementation of the project.

Based on the results of a cost comparison analysis between precast concrete and conventional concrete systems in two case study buildings, it can be concluded that, in general, the precast system offers advantages in terms of direct construction cost efficiency. The total construction cost using the precast concrete method was recorded at IDR 19.867.271.759,68 for Building A1 and IDR 14.294.887.434,88 for Building A2. Meanwhile, the total construction cost using the conventional method amounted to IDR 17.605.624.685,13 for Building A1 and IDR 12.744.226.867,01 for Building A2.

The cost differences of IDR 2.261.647.074,55 (12,85%) for Building A1 and IDR 1,550,660,567.87 (12.17%) for Building A2 indicate that the precast system is more cost-effective in nominal terms than the conventional system. Although the percentage difference is relatively small for Building A1, the cost savings

achieved in Building A2 are considered quite significant for medium- to large- scale building projects. Therefore, from the perspective of direct construction costs, the precast concrete system can be considered a more economical option.

In terms of the duration of the main structural works, the precast system showed superior performance compared to the conventional system. In Building A1, the implementation of the main structural works using the precast method can be completed in 203 days, while the conventional method takes up to 335 days. For Building A2, the precast system completed the work in 140 days, while the conventional method required 170 days.

Thus, the accelerated execution time obtained from using the precast system was 132 days for Building A1 and 30 days for Building A2. This shows that the precast system has significant advantages in the efficiency of implementation time, which not only has an impact on reducing indirect costs, but is also able to minimize the risk of project delays. This speed of implementation makes the precast system a strategic alternative for projects with tight time constraints or targets to accelerate the construction schedule.

This research has limitations in the scope of the case study, which is limited to only two buildings, and only focuses on comparing the direct costs of the main structural elements such as columns, beams, and floor plates. In addition, the cost calculation data was obtained through self-estimation due to limited access to real data from the implementing contractor, which may affect the accuracy in representing actual field conditions.

For future research, it is recommended that analysis be conducted with a more diverse project scope, both in terms of building type, geographic location, and project scale. In addition, further research can integrate indirect cost aspects in more detail, including mobilization costs, maintenance costs, and the risk of time delays. A more comprehensive approach such as the use of Building Information Modeling (BIM) or integration with real data from actual project implementation can also improve the accuracy of the analysis results and their implementation in construction practice.