Model based estimating to inform Target Value Design: -

In tradition project management approaches, design is the prime factor which affects the cost of a

project which many a times lead to overshooting the target cost value. In Target Value Design (TVD) or

Target Costing method – cost is the motivating factor for design considerations. Cost defines the design

and thus helping to achieve the completion of project within target cost. TVD is used for applying Lean

Construction Methods in healthcare projects.

Project background: -

- Integrated Form of Agreement (IFOA) used as contract method – similar to IPD

- Made highly integrated design employing Lean Construction Methods like Value Stream

Mapping, Work Structuring and Production Control, and TVD

- Also used BIM for MEP coordination, quantity takeoff and estimation to support TVD

Model Based Cost Estimating

- TVD or Target Costing process uses cost as an input to design

- Model-based cost estimating – combine designed 3D model with cost data from estimators

- Better than using 2D drawing for estimation –faster and less prone to errors and omissions

- BIM and model based cost estimating together have a bright future, but current implementation

of these two together is not on many projects

- Interoperability issues relating to different cost estimating softwares used by different trades

causes a lot of problems in effective implementation of model based costing.

- Currently, there are two approaches available for the same: -

o Option 1 includes different modelling softwares which require different cost estimating

platforms. Many 3D modelling companies are working on developing there won cost

estimating platform, and thus there seems to be issues with interoperability and

flexibility in future.

o Option 2 includes neutral platform used by cost estimating sources. They either develop

plugins for different 3D modelling softwares so that their data can be used by them or

all cost estimating sources can develop their data using single creation scheme which

will make data operable on all 3D softwares.

Challenges in implementing Model-Based Cost Estimating

- Challenges are not substantial software-wise. It can be done easily by buying the software –

though who will pay for the buying cost is debatable

- Transition from traditional methods to model based cost estimating would require trainings to

be given to people and making them adept at using the software platform

- Initially model based cost estimating may take more time when compared to traditional

methods as estimators will be in the learning phase. Process of model based cost estimating will

become faster as estimators become accustomed to new methods.

Lessons Learned from SMCCV project done by DPR

- Implementation is easier if model based cost estimating is encouraged by higher management

- Contract terms should support collaborative work environment for all stakeholders – and also

mandate the implementation of model based cost estimating methods, and encourage all to

make efforts so that it can be implemented effectively

- All costing cannot be done using model based method alone as everything cannot be accurately

modelled

- Transition from traditional to new method takes time and effort but it proves beneficial in long

run – it requires a lot of preplanning and training, and should be implemented in the project as

early as possible preferably by the end of conceptual design phase

- Quantities of the new model should be checked by traditional methods to check for accuracy of

software

Rethinking the Cost Estimating Process through 5D BIM: a Case Study

Traditionally Cost Estimating is done after completion of conceptual designs, which is too late for making

any informed decisions about the cost of the project. To be able to perform value engineering and cost

estimation from the beginning of the design phase would enable a faster and cost effective approach to

project delivery, high quality standards, and more control and predictability for the owner.

- AEC companies facing a scenario change – moving from CAD to BIM. BIM also offers a new way

to cost estimation

- BIM model can be used for simulating construction (4D BIM), and it can also be used to provide

quantities in real time for cost estimating (5D BIM)

- BIM model can provide quantities but it cannot fully replace costing softwares. To make date

from BIM effective in cost estimating we have following options

o Exporting BIM data to costing softwares

o Use a BIM QTO tool

o Link BIM tools directly to estimating softwares

Challenges in BIM based Cost Estimation

- BIM cost estimating is not mature enough

- Problems of interoperability in softwares used

- Uniform software which can be used by all trades is not available

- New organizational system has to be formed which focuses on BIM and its related applications

- Roles of all the stakeholders will change according and as such new contractual agreements will

have to be made – workflows have to be designed keeping BIM in mind

- As technology is not mature enough, so it will take a significant amount of time and money to

get used to and to implement it initially – cultural shift and required training

- Integration of workflow b/w 3D, 4D and 5D applications – 3D model gives quantities that form a

base for 4D and 5D BIM. Quantities from 3D are not accurate most of the time and do not

include temporary structures etc. in it and thus will not reflect the true cost

Case Study for BIM based Cost Estimating

- Traditional approach is linear, straightforward and unsophisticated. 2D drawings are used for

QTO and cost estimation, but new project delivery methods have opened doors for adoption of

new methods for cost estimation and 5D BIM

- 5D BIM is not yet perfect and requires different softwares, tools and plugins to be utilized for

different phased of the project.

o DProfiler and Smart BIM QTO are used in the preliminary design phase of project when

different alternatives are compared – these softwares are less complex and can be used

easily

o Autodesk QTO, Innovaya, VICO and Tocoman are used for precise estimation. Cost

estimating has to be linked with clash detection, and thus 4D BIM softwares have to

incorporated with 3D BIM to obtain cost estimating in 5D BIM

o The company in this case study used Timberline software for cost estimation, and for

successful implementation of 5D BIM Timberline’s database has to be catered according

to Revit model

o Once these challenges are overcome, BIM 3D model along with 4D BIM softwares form

the central platform through which all cost estimating is done using Timberline Cost

Estimating Software

o Interoperability between all these softwares used during preliminary phases and more

advanced phases of project is the key factor in 5D BIM i.e. BIM based Cost Estimation