How to Use BIM in Preliminary Design: Key Points for Improving Accuracy and Efficiency

1. Introduction: Growing Interest in Using BIM for Preliminary Design

In recent years, there has been increasing momentum in the architecture, civil engineering, and infrastructure sectors to actively use BIM (Building Information Modeling) from the preliminary design phase. Preliminary design refers to the early-stage design and rough estimation of construction costs conducted before detailed design begins; it is a critical phase for determining project direction and budget feasibility. If appropriate planning and cost understanding are not achieved here, significant rework or budget overruns can occur later, potentially impacting the entire project.

BIM has traditionally been emphasized for construction and facility management, but the merit of using 3D models to centrally manage information from the early design stages has been re-evaluated, and interest in introducing BIM into preliminary design is growing. Since fiscal year 2023, the Ministry of Land, Infrastructure, Transport and Tourism has also announced a policy to apply BIM/CIM in public projects as a general principle, and the use of 3D model-based reviews and quantity takeoffs from the design stage has begun to be required. Against this background, a wide range of stakeholders—architectural designers, civil engineering consultants, cost estimators, and municipal staff—are looking to BIM in preliminary design for improved accuracy and efficiency.

This article explains the concrete benefits and practical techniques of incorporating BIM into preliminary design. First, we clarify BIM basics and how it differs from traditional methods, then explain why BIM excels in the preliminary design phase. We then introduce practical points useful in the field, such as automated quantity takeoff and cost estimation using BIM, accuracy improvements through visualization of earthwork and floor area, and streamlining design-option comparisons. We also cover cautions and tips for implementation and promotion, and as a bonus touch on site verification and point-cloud utilization using LRTK surveying tools that work well with BIM, introducing the potential for integration with the latest simplified surveying methods.

2. What Is BIM? Basic Definition and Differences from Traditional Design

BIM stands for Building Information Modeling and is a design approach that centrally manages all information about buildings and infrastructure structures on a 3D model. Specifically, building or structural components (columns, beams, walls, equipment, etc.) are represented as digital 3D models, with attributes such as dimensions, materials, finishes, and cost assigned to each. Once a single BIM model is created, plans, elevations, and sections can be generated automatically; because these drawings are linked to the same model data, updates can be made consistently throughout the set when design changes occur. This is a major difference from traditional 2D CAD-based design. In conventional methods, each drawing often requires individual edits, leading to inconsistencies and omissions, whereas with BIM you only modify the single model and related drawings and quantities update accordingly.

BIM also dramatically improves information sharing and collaboration among stakeholders. If a BIM model is shared in the cloud, architects, structural and MEP engineers, construction personnel, and clients can all reference the same up-to-date information in real time. Information that used to be exchanged via drawings and Excel can be centrally managed on BIM, reducing risks like “not knowing which drawing is the latest” or “forgetting to include quantities due to oversights.” Furthermore, BIM can be linked with 4D (schedule) and 5D (cost) information, enabling seamless integration from design-stage schedule reviews to preliminary cost estimation. In short, BIM is not merely a 3D design tool but a digital platform that supports the entire project lifecycle.

In traditional preliminary design, it was common to perform rough quantity calculations by hand from plans or estimate construction costs from unit prices per area derived from past similar projects. However, that approach has limitations in accuracy and requires recalculation whenever drawings change. By using BIM, you can shift from such experience- and intuition-based estimates to quantitative, data-driven preliminary estimates.

3. Why BIM Excels in the Preliminary Design Phase

Why is it advantageous to use BIM at the preliminary design stage? The main reasons are as follows.

• Improved cost forecasting accuracy: BIM models can automatically aggregate quantities and areas, improving the accuracy of preliminary construction cost estimates. By obtaining near-accurate cost information early, you can reduce the risk of budget overruns and appropriately control design content. For example, if a preliminary estimate is performed in BIM during the schematic design, you can avoid situations where substantial cost overruns are revealed after detailed design, forcing a redesign.

• Clarified spatial imagery and deeper review: BIM’s 3D models can visualize three-dimensional spatial arrangements and level differences that are difficult to grasp from 2D drawings alone. This makes it easier for clients and stakeholders to imagine the finished product and facilitates smooth sharing of design intent. As a result, consensus-building and feedback during the preliminary design phase become easier, potentially reducing change requests in later stages.

• Flexible response to design changes: In preliminary design, it is common to revise plans—for example, “Plan A exceeds the budget, so consider alternative Plan B.” With BIM, you can quickly copy a model and modify it to create alternatives, or change specific elements (such as room sizes or structural grids) and immediately verify the overall impact. Compared to traditional CAD drafting, the time required for design changes is greatly reduced, enabling efficient comparison of multiple options and facilitating pursuit of the most optimal plan.

• Enhanced collaboration among stakeholders: Using a BIM model enables designers, estimators, and clients to communicate while referencing a common model. For instance, municipal staff or owners can review the model from the design stage and discuss in real time “how changing this specification would affect cost.” Estimators can obtain quantities directly from the model and work with designers to adjust costs. BIM lowers the barrier between design and estimating, promoting collaborative efforts across the team to achieve project goals.

As described above, BIM enables early problem detection and rapid countermeasure planning in the preliminary design phase, making it a powerful tool for project success. The traditionally experience-reliant early planning stage is increasingly shifting to a scientifically backed approach supported by BIM data.

4. Automated Quantity Takeoff and Preliminary Cost Estimation with BIM

One major advantage of using BIM in preliminary design is the efficiency gained through automation of quantity takeoff. In quantity surveying for architecture and civil engineering, it is essential to read quantities such as wall areas, column counts, and pipe lengths from drawings and aggregate them—work that has historically been very labor-intensive. Experienced estimators used to check each drawing and enter quantities into Excel sheets; this process is not only time-consuming but prone to human error.

With BIM software, you can aggregate quantities such as lengths, areas, volumes, and counts with the press of a button based on the component information included in the model. For example, if components such as the building’s floor area, total exterior wall area, or structural frame volumes are already input into the model, they can be calculated automatically. Designers can obtain preliminary quantities and estimate preliminary construction costs themselves within BIM, reducing the need to hand over drawings to the estimating department for calculation. Enabling parallel work between design and estimating also shortens the project’s overall lead time.

Moreover, if you link unit-price information to the quantity data, the preliminary estimating process can also be automated and accelerated. By setting unit prices and labor rates for each component in the BIM software, preliminary construction costs can be calculated simultaneously with model aggregation. If you build an operation where quantity tables exported from the BIM model are imported into commercial estimating software or an internal historical database, you can minimize manual recalculations. In practice, attempts to use estimating systems that integrate with BIM data and automatically update estimate documents when design changes occur are already underway.

However, there are some cautions when performing quantity takeoff with BIM. First is the accuracy of model input. Elements not reflected in the BIM model will not be counted in the quantities. In preliminary design, detailed elements may be omitted from the model, so adjustments may be required later. For example, you might model the structural frame with assumed cross-sections to calculate approximate concrete and rebar quantities, then input those rough quantities into an estimating program to obtain a preliminary construction cost. Also, if the model is incomplete or attributes are incorrectly set, the output quantities will contain errors. Therefore, it is important to establish internally at model creation what level of information accuracy will be assigned.

Second is differences from estimating standards. Automatically generated quantities may not strictly follow specific estimating standards. For example, architectural estimating rules may have unique conventions like deducting openings or rounding rules; BIM software may meticulously subtract every opening, leading to discrepancies between BIM aggregation and quantities calculated per estimating standards. While some variance is acceptable at a preliminary level, final construction cost calculation should be reworked in a dedicated estimating system or adjusted based on experience. BIM quantities should be treated as “reference values for rapidly obtaining a preliminary estimate,” with final verification by specialists.

With these points in mind, automating quantity takeoff and preliminary estimating with BIM becomes a powerful tool for quickly understanding approximate project scale. It significantly reduces laborious estimating tasks while allowing cost-conscious planning from the design stage—truly a “two birds with one stone” effect.

5. Improving Design Accuracy by Visualizing Earthwork, Floor Area, and Structural Elements

A key advantage of BIM is the ability to visualize and verify various project elements from the early design stage. In particular, “earthwork,” “floor area,” and “building structure” are three items prioritized in preliminary design, and BIM is an exemplary tool for improving accuracy in these areas.

First, regarding earthwork. For civil infrastructure projects and site development in building projects, calculating cut-and-fill volumes—the earthwork quantities—is crucial. Traditionally, this was done by generating sections from topographic maps or estimating with empirical factors, but with BIM/CIM you can overlay a 3D terrain model and your design model to visually and quantitatively determine cut-and-fill volumes. For example, placing the building foundation model on a site ground model can automatically calculate excavation volumes for foundations. This enables high-precision projections of earthwork costs and spoil disposal volumes from the initial stage.

Next, floor area. In architecture, gross floor area and room areas are fundamental to the basic plan and are important for checking compliance with zoning regulations such as floor-area ratio and building coverage ratio, as well as room size requirements. If spatial (room) elements are defined in the BIM model, floor area aggregates per floor and per room can be generated instantly. This makes it easy to check deficiencies or excesses in area from the design stage, helping to plan efficiently without waste. For example, if the total floor area grows too large compared to the initial plan, you can detect it immediately and adjust the plan early to prevent cost overruns.

Then, visualization of building structure. Although detailed structural design may not be performed during preliminary design, representing a rough structural frame in the model is effective for checking alignment between architectural and structural planning and for preliminary structural quantity estimation. BIM can show the placement of structural elements like columns, beams, and walls in 3D, enabling early detection of issues such as “the span in this plan is too long, causing large beam depths” or “column positions interfere with parking layouts.” Calculating concrete volumes or steel weights from the structural model aids in estimating structural frame construction costs. Harmonizing design and structure from the preliminary stage can prevent catastrophic situations where, after structural design progresses, the original architectural scheme is found to be infeasible and requires complete redesign.

Thus, visualizing and quantifying project elements with BIM greatly enhances design accuracy. Issues that might be overlooked in drawings can be exposed on the model and evaluated together with quantitative data, enabling evidence-based decisions. As a result, the reliability of the preliminary design—both the validity of design content and the accuracy of cost estimates—is markedly improved.

6. Speeding Up Design-Option Comparison and Supporting Designers' Decisions

In preliminary design, it is common to compare multiple design options to meet performance requirements and budgets. BIM strongly supports this process. It is easy to create alternative designs derived from a single base model. For example, copy base Plan A in the model and create Plan B by adding one floor to secure floor area, or create Plan C by reducing scale to lower costs—such variations can be generated quickly in the model. Traditionally, each option required drafting separate drawings and calculating quantities for each, which demanded enormous effort; with BIM you can assemble data for multiple options in a short time.

Comparisons among options can be made based on BIM’s quantitative information. For instance, by aggregating total floor area and major component quantities for Plans A, B, and C and estimating preliminary construction costs, you can evaluate options with concrete indicators, such as “Plan B is the least costly, but Plan A offers superior spatial composition.” Presenting the completed-image using 3D views and renderings makes it easier to obtain client or management approval. The ability to present design options with visuals + data supports decision-making with both intuition and persuasive evidence.

The acceleration of revision work is also notable. When the model is modified in BIM, associated drawings and quantities update automatically, reducing time spent on consistency checks and drawing corrections after design changes. For example, you can instantly see “if we shrink the room a bit, how many square meters are reduced and how much cost falls.” This shortens the trial-and-error cycle, enabling consideration of more options or reallocating time to other creative tasks.

BIM is therefore more than a drafting efficiency tool for designers; it is an information-gathering and analysis tool that supports better decision-making. Modern designers are expected to consider not only spatial beauty and functionality but also cost and constructability comprehensively. BIM helps gather these multifaceted decision-making materials early, assisting precise decisions at critical project junctures.

7. Cautions for Implementation and Tips for Promotion

When introducing BIM into preliminary design, there are several key cautions to keep in mind, and planning points to ensure smooth implementation and promotion. The main cautions and promotion strategies are summarized below.

Main cautions when implementing:

• Initial costs and environment setup: Initial investment is required for BIM software licenses and enhanced hardware performance. Allow sufficient time to select BIM tools suitable for your company and to set up the PC environment. Pay attention to software interoperability (e.g., data exchange when different BIM tools are used for architecture and civil engineering).

• Human resource development and internal structure: Mastering BIM requires skills different from traditional CAD. Plan to develop BIM personnel internally and consider external training, e-learning, or expert advice as needed. Since proficiency takes time during the initial rollout, avoid peak seasons and set pilot projects for practice.

• Changes to workflows: BIM introduction changes the workflows of design, estimating, and construction. For example, you may need to develop a certain level of detailed modeling during schematic design, increasing initial-stage workload. While this reduces rework later and improves overall efficiency, coordinating with existing internal and external workflows is a challenge. Align roles and processes with stakeholders and subcontractors in advance.

• Data standards and quality control: Without internal modeling standards, element names and layer structures can vary by person, making subsequent quantity takeoff difficult. Establish rules for component codes, level division, and attribute input, and implement mechanisms to control model quality. Conduct regular model checks to identify inconsistencies or failures.

• Stakeholder awareness alignment: If clients or contractors are unfamiliar with BIM, they may say “I don’t know how to view it” or “I still want conventional drawings,” even if you provide a model. Explain BIM benefits in advance to obtain understanding, and consider providing 2D drawings or tables in parallel as needed. Prepare transitional measures until everyone becomes accustomed to BIM.

Promotion points for successful BIM implementation:

• Commitment from management: Organizational support is essential. Have management clearly communicate that BIM will be promoted as part of digital transformation (DX) and position it as a company-wide initiative. Rather than leaving it to individual staff, create a cross-departmental project team to drive adoption.

• Clarify purpose and stage-wise plan: Define the objectives for using BIM in preliminary design (e.g., improving cost accuracy, streamlining operations, enhancing information sharing) and set achievement indicators. Instead of rolling out BIM to all projects at once, start with pilot projects, accumulate experience, and gradually expand the scope. Sharing successful cases internally helps smooth diffusion to other teams.

• Establish internal rules and training: As mentioned, set internal rules for BIM modeling and operations. Prepare templates, standardize naming conventions, and define model Level of Development (LOD) criteria; document and share them. Invest in education not only for tool operation but also to help staff understand “how BIM changes business processes.”

• Utilize external resources: If you lack sufficient in-house expertise, enlist external BIM consultants or vendors. Having experts help establish modeling standards and participate in projects to transfer skills through practice can accelerate start-up. Refer to other companies’ cases and national or industry guidelines (e.g., materials from BIM promotion councils) and adapt them to your organization.

• Measure effects and provide feedback: Quantitatively measure BIM implementation effects (e.g., schedule reductions, improved estimate accuracy, labor savings) and provide feedback to stakeholders. Demonstrable results make internal understanding and cooperation easier and support further investment and challenges in subsequent projects.

By addressing these points and proceeding carefully, introducing BIM into preliminary design is not necessarily a high hurdle. Many report that once they experience the benefits, they “can no longer go back to the old way.” Prepare thoroughly, build small successes, and gradually embed BIM usage in your organization.

8. Conclusion: The Future of Preliminary Design with BIM

We have reviewed BIM utilization techniques in preliminary design, focusing on improving cost accuracy and streamlining design tasks. BIM transforms the early-stage design process—which traditionally relied on experience and intuition—into a data-driven, transparent process. High-confidence preliminary estimates through automated quantity calculation, deeper review and smoother consensus-building via 3D models, and fast comparison and modification of design options—all of these increase project success rates and reduce wasted cost and time.

As BIM becomes more widespread across the industry, the way preliminary design is conducted will also change significantly. Clients will be able to make decisions earlier with higher-quality information, and designers, estimators, and constructors may routinely collaborate on a common platform from design onward. With policy support from the government, for example, pilot trials of building permit applications using BIM models in some municipalities may begin after 2025, and by around 2030 a fully digitalized flow from design through review, estimating, and construction could become standardized. Using BIM in preliminary design can be seen as a first step toward that future construction DX.

Of course, introducing BIM does not guarantee immediate success; issues such as human resource development and establishing operational rules must be tackled. However, the returns once these are overcome are considerable. In BIM-enabled projects, many success stories have been reported—“rework due to design changes decreased significantly,” “disputes caused by misunderstandings with the client were resolved,” “time required for estimating was reduced by about 30% compared to before,” etc. As these results accumulate, BIM will become the new norm even in a conservative industry, and preliminary design practices will continue to evolve.

If you are considering trying BIM for preliminary design, start with a small project or model only part of the project—it’s fine. Try it once; you will likely be surprised by its efficiency and usefulness. With BIM, realize “fast, accurate, and collaborative” preliminary design and increase your project’s chances of success.

9. Bonus: Streamlining Site Verification with LRTK Surveying Tools that Pair Well with BIM

Finally, as a tool that can streamline site surveying and investigation related to preliminary design, we introduce LRTK surveying, which is attracting attention. To make effective use of BIM models, it is important to grasp accurate as-built data of the site and existing structures. Traditionally, this required on-site surveys by surveyors or terrain model creation via drone photogrammetry, but the recently introduced LRTK (high-precision real-time kinematic) surveying tools make it easier to acquire 3D site data and integrate it with BIM.

LRTK surveying tools are an innovative measurement system that uses smartphones or compact GNSS receivers to obtain position information with centimeter-level accuracy (half-inch accuracy). For example, with an LRTK device that attaches to a smartphone and a dedicated app, anyone can easily measure positional coordinates of terrain and structures or, combined with a smartphone’s built-in LiDAR sensor, quickly collect point cloud data (3D scan data). Compared to traditional surveying instruments, these tools are inexpensive and easy to carry, making it feasible for designers themselves to perform simple surveying on site.

Combining LRTK surveying with BIM dramatically enhances the efficiency of site verification and data utilization in preliminary design. For instance, importing point cloud data of terrain, boundary lines, and building positions obtained by LRTK into BIM/CIM software allows you to review plans on an accurate as-built model. Designing on a model that faithfully reproduces site level differences and relationships with surrounding buildings improves the accuracy of earthwork calculations and lets you verify how the planned building will appear in context. Additionally, using the LRTK app’s AR (augmented reality) features, you can overlay BIM design models onto live site imagery. Viewing the model through a tablet or smartphone makes it feel as if the building already exists on site, enabling intuitive checks of whether a plan fits the site and harmonizes with the surroundings.

LRTK surveying tools are already being introduced by some municipalities and construction companies for rapid terrain assessment at disaster sites, infrastructure inspection, and obtaining as-built BIM data at design sites. Combining BIM and LRTK smooths the bridge between digital and physical, transforming site verification from paper drawings and intuition to a data-driven process. It effectively links “plans made in BIM” with “the real conditions on site” at high accuracy.

It is highly valuable to incorporate such advanced surveying techniques into the preliminary design process when appropriate. For example, scanning an entire site with LRTK in the early stage and creating a terrain model from the point cloud to incorporate into BIM enables designers to begin planning without waiting for detailed survey drawings. Later, when design options are finalized, projecting the model on site for verification allows early detection and correction of discrepancies between design and site conditions.

The [LRTK surveying tool](https://www.lrtk.lefixea.com/), which extends BIM’s usability to the site, is truly a technology well-suited to preliminary design. By smartly combining digital tools, achieve consistent efficiency and accuracy from planning through to the field.