Construction cost estimating: how to dynamically obtain a cost estimate using the 5D BIM model
How long does it take you to prepare a cost estimation and predict the overall cost of a construction project? How accurate are results?
Cost estimating is probably one of the most stressful aspects of the construction process being time-consuming and error-prone, without considering having perhaps to update it manually as project changes are applied.
5D BIM modelling not only allows you to estimate total costs accurately, but also to model costs across time as the project progresses by calculating quantities directly from the BIM model.
Let’s take a look at what 5D BIM is and how AEC professionals can harness 5D BIM for improving their cost estimation and budget analysis endeavours.
What is 5D BIM?
5D BIM modelling is the process of creating intelligent connections between the 3D digital model (which defines the geometry of the building) and the cost information for a construction.
The result is a 5-dimensional (5D) information model complete with the attributes needed to estimate the overall cost of the project.
In fact, when working with a BIM model, cost estimation can be obtained automatically as the prices of each work type or supply are associated directly to the parametric objects of the 3D geometric model. As well as being a more streamlined and faster process for the designer/cost manager, this method allows full control over the operations to be carried out and results less risky in terms of errors. The integration of BIM with 5D simulation models allows you to view the progress of activities, the related costs over time and whenever changes are made to the project.
For example, when changing the size of a window it automatically updates the quantity and consequently also the cost of that specific work type.
Using a 5D model provides methods for extracting and analyzing costs, as well as evaluating alternative scenarios, resulting more accurate and predictable estimates, quantities, materials, equipment, and labor.
To estimate the costs of works construction/maintenance/management, with a traditional method, it is necessary to:
- accurately identify the work to be carried out and the relevant items in the price list
- calculate quantities
- organise measurement data in a logical sequence
- assess materials, rules and units of measurement.
The more accurate the assessments, the lower the risk of errors.
Differently, with a digitized process such as 5D BIM modelling, you can take advantage of certain automatisms that create an accurate correlation between the 3D model entities and their cost items.
The benefits of 5D BIM modelling are:
- greater cost control – every single detail of the bill of quantities is directly tracked and monitored, ensuring accuracy of measurements and cost control for construction companies and the client
- fast quantity assessment – the preparation of an accurate model-based quantity survey means greater efficiency and optimised workflows within the BIM process design teams.
- quality of work – greater control and processing speed leads to improved productivity, which translates into cost savings for the contractor and design firms
- more accurate evaluations – collaboration between all parts of the construction process in BIM mode allows everyone involved to keep track of project costs even when making changes to the project
- greater accuracy and predictability in the analysis of project costs, changes in quantities and materials, equipment and labour – the integration of BIM with 5D BIM simulation models enables the development of more efficient and sustainable buildings.
The implementation of BIM in cost analysis through all stages of the construction process provides accurate and detailed information, enabling designers to make correct and informed decisions, thus reducing the need to revise design choices during construction.
“BIM dimensions” refer to aspects and information that come into play in the process of digitization of a construction project.
BIM is more than just the three-dimensional (3D) modelling for which it is known and can embrace other “dimensions” that serve to add useful information to the asset to be built or managed:
- 3D – three dimensional graphical information.
- 4D – modelling scheduling information to model construction sequences
- 5D – cost management, construction cost estimating, etc.
- 6D – environmental, economic and social sustainability impact studies
- 7D – facility management: planning and management of maintenance operations throughout the building’s lifecycle.
In addition to the 7 standard dimensions, there is an open debate on the three “new dimensions of BIM”:
- 8D – safety during design and construction phases
- 9D – lean construction
- 10D – industrialisation of construction.
The main features of 5D BIM modelling software
Construction estimation software allow you to take advantages of 5D BIM modelling and to obtain an automatic project cost estimate.
Specifically, 5D BIM software allow you to:
- link each model object to a relative item in the reference price list
- automatically obtain the project cost estimate
- update the estimate in real-time whenever modifying the model
- print, export and re-process the cost estimate.
The ideal would be to have a single BIM software to manage all the dimensions of BIM, i.e. all the aspects that come into play in the design of a project.
To obtain an automatic estimate directly from the 3D model, you can use Edificius, the architectural BIM design software.
With Edificius, you can calculate your cost estimate project directly from the BIM model, without any additional estimating software or plug-ins.
What’s more, with a single tool you can:
- create the entire project 3D model (from interior design to the design of outdoor spaces)
- model MEP systems
- manage historical buildings and point clouds
- predict construction time
- automatically estimate the construction costs of the project
- present the project with visual graphics, renderings, videos and virtual reality.
The challenges of implementing 5D BIM
Despite the many advantages of implementing 5D BIM, the process of adopting this methodology is still rather slow.
The causes are:
- lack of a single software solution for the implementation of BIM 5D
- initial investment of resources
- conversion of business processes.
In conclusion, the implementation of the BIM 5D methodology involves an initial effort due to the acquisition of new technologies, tools and properly trained personnel, but the benefits amply repay the investment of resources and contribute to a more virtuous project design process.