Traditional and BIM Approach in Quantity Surveying

Introduction

Quantity surveying in the Engineering and Construction industry focuses on the quantities, cost, and budget of the projects. A quantity surveyor is associated with the planning, design, construction (or demolition/reconstruction) phases. Right from a plan being drawn and until a large construction project has been completed, a quantity surveyor is likely to be involved in a legal, technical and financial capacity.

A Quantity Surveyor is an expert in the art of costing a building/infrastructure at all its stages who offers expert advice on construction costs.

A Quantity Surveyor will be responsible for helping to estimate costs, quantities, and project timelines and providing this information to clients. He/She will be liaising with a variety of other teams and helping to keep a project on track.

Importance of Quantity Takeoff and Required Documents

The quantity of material in a project can be accurately determined from the drawings. The estimator must review each sheet of the drawings, calculate the quantity of material and record the amount and unit of measure. Each estimator must develop a system of quantity takeoff that ensures that a quantity is not omitted or calculated twice. A well-organized checklist of work will help reduce the chances of omitting an item. The estimator must, also, add an appropriate percentage for waste for those items where waste is likely to occur during construction. The material quantity takeoff is extremely important for cost estimating because it often establishes the quantity and unit of measure for the costs of labor and contractor equipment.

When preparing their cost estimates, estimators typically begin by digitizing the architect’s paper drawings, or importing their CAD drawings into a cost estimating package, or doing manual takeoffs from their drawings. All of these methods introduce the potential for human error and propagate any inaccuracies there may be in the original drawings. By using a building information model instead of drawings, the takeoffs, counts, and measurements can be generated directly from the underlying model. Therefore the information is always consistent with the design. And when a change is made in the design – a smaller window size, for example – the change automatically ripples to all related construction documentation and schedules, as well as all the takeoffs, counts, and measurements that are used by the estimator.

The time spent by the estimator on quantification varies by project, but perhaps 50-80% of the time needed to create a cost estimate is spent just on quantification. Given those numbers, one can instantly appreciate the huge advantage of using a building information model for cost estimating. When you do not require manual takeoffs, you can save time, cost, and reduce the potential for human error.

Traditional Approach

To produce a quantity takeoff, the estimator or contractor will need to work off drawings, blueprints, or models. The estimator will prepare a list of each material required to complete a construction project from the design paperwork.

  • Cost estimation for building projects traditionally starts with quantification – a time‐intensive process of tallying components from printed drawing sets, or more recently ‐ 2D CAD drawings.
  • From these quantities, estimators utilize methods from spreadsheets to costing applications to produce the project cost estimate.
  • This process is prone to human error and tends to propagate inaccuracies that creep into the tallies.
  • Currently, quantification is also time‐consuming – it can require 50% to 80% of a cost estimator’s time on a project.

What stages in the project should a Quantity Take Off take place?

Quantity takeoffs are generally performed early on during the bidding process.

During the estimation process, an estimator may have to make frequent adjustments to the quantity takeoff, typically due to:

  • Design changes
  • Additional engineering requirements
  • Changes in what the client wants.

Thus, the quantity takeoff is often a living document that undergoes many changes until a design is decided and a bid is secured.

While this may not be the case for smaller projects, large or complex projects will almost certainly require many revisions to the quantity takeoff.

The manual process requires a great deal of time for revising the BOQ to accommodate design changes. Hence, the BOQ is often out-of-date.

How are costs measured in Quantity Take-Offs?

Quantity takeoffs fulfill two basic functions in a construction cost estimate.

First, they detail what materials need to be purchased to complete a project.

Second, they provide a total material cost for a project, which is then incorporated into a detailed cost estimate. To determine a total cost estimate, the contractor or estimator will need to determine the cost for each specific required material.

Traditionally followed Quantity Takeoff and bill generation is a very time-consuming process that is prone to error.

• Errors associated with moving data between files  

• Risk of double counting  

• Risk of missing elements  

• Multiple 2D drawings etc.

BIM Approach  

Although the concept of Building Information Modeling (BIM) is slightly practiced in the Indian construction industry, it is likely to become the project delivery standard in the future. Introduced with the vision “sustainability by building smarter”, BIM will improve the performance of building professionals. The current knowledge does not adequately explain how the functions of a Quantity Surveyor are affected by BIM

BIM has the potential to influence every characteristic of the construction industry together with construction professionals.

The BIM 5D model has the potential to perform an automatic analysis of all materials and components and to derive their quantities directly from the model.

Usage of BIM as a Quantity Surveying Tool

BIM suggest that a detailed building model would provide greater certainty over the quantities of material, and therefore, BIM would produce a more reliable cost estimate compared to the traditional process.

Large clients who have their in-house cost database can directly derive their estimates during the early stages of the project using BIM-based estimating tools. Therefore, they can afford to do without the services of the QS.

The Process Map of this comparison test is illustrated below


Figure 1 : Process Map

A research project result when Traditional and BIM approach towards quantity surveying was compared, In general, the research method is robust to support the conclusions.

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Capabilities of BIM applications pertaining to the Traditional Quantity Surveying tasks

  • Quantity Take-off
  • BOQ Preparation
  • Cost estimation
  • Cost planning
  • Cost control
  • Material procurement
  • Payment applications
  • Life cycle costing

BIM in the point of ROI

According to McGraw Hill SmartMarket Report(2014), a survey was conducted in 10 countries which consisted of 727 contractors. The survey concluded that the percentage of BIM involvement in the construction industry will increase by 50% on average. A positive ROI(Return on Investment) was reported by three-quarters of all the contractors that were

surveyed. Most of the surveyed contractors estimated the ROI on their BIM implementation between 10% to 25% and about 60% of contractors believed that further advancement in BIM visualization would have the most positive impact on BIM ROI

Challenges of BIM for QS practice

  • Proper technical knowledge and Modelling practices

It is hard to adopt new information technology (IT) in the industry due to technical reasons. Problems such as the lack of support system, difficulty to understand the complex software and also the low number of skilled technical experts and modelers are among the reasons

  • Change in the process

For an organization to adopt BIM fully, there will be essential and basic changes to its operational processes. Once a company successfully adopts BIM, the process of design will be brought forward to the start of the project.

  • Professional support

BIM has been known to provide an interchange of electronic data without boundaries, the management of professions, trades, and industries are still kept fixed in cultural and geographical boundaries, as well as political identities.

  • Finance and Time

In order to implement BIM successfully, firms need to upgrade their hardware, obtain the necessary software, and also require their employees to go for the BIM training in order to transform a 3D environment into a complete BIM system. The firm needs to periodically upgrade its hardware to run the processing software, and this has become a significant barrier particularly for small-medium size enterprises.

  • Teamwork and Collaboration

Even though the implementation of BIM has offered new ways for cooperation between the project team, some problems may arise during its application. For instance, an issue may occur when the method for sharing model information among the team member is not being determined. If traditional drawings on paper have been used by the architect, then a third party will have to construct a model to be used for the estimating and planning of the construction project.

Conclusion

Many studies prove that advancement in technology has taken the AEC industry into the computer-based age. It has proved to be a promising technique and has caused better changes in the entire construction industry. The BIM is applicable throughout the lifecycle from the planning stage to the implementation stage to the operational stage. BIM provides the possibility for the optimization of complex projects. Since 5D-BIM is multidisciplinary and includes various platforms and related integrations, successful research on each of its aspects and its viability could help the construction sector in India to leap from its traditional method to the concept of Building Information Modelling.

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Author : Naveenkumar Naigpogu

Follow Desapex sales@desapex.com

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