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Efficiency in cost plan­ning

Cost plan­ning and cost control with BIM

 

Gruner Ltd
Christian Brendelberger, Architect (UAS)
Christian[punkt]Brendelberger [ät] gruner[punkt]ch

Costs have always been and still are a central theme of every construction project, be it new construction, alteration or renovation. In recent years, however, cost planning has increasingly become important as a control element in the planning process. BIM is creating entirely new possibilities for cost controlling.

Building Information Modeling (BIM) not only provides a three-dimensional representation of the building in the virtual world, but also provides data on the properties of all building components, their relationship with each other and with the overall structure of the building. People are speaking of the fourth dimension in connection with the integration of schedule management and the fifth dimension regarding cost planning. If lifecycle management also flows into building data modeling, this then describes the sixth dimension. All information has its origin in the model space. This means that there is no unreferenced data. The building data model is therefore a holistic, integrated image of the planned or already constructed building. Instead of dimensions, one could also speak of integration levels.

Integral digital

The method of building data modeling with BIM aims at optimized planning, execution and management of real estate properties; not only the building itself but also the actual, spatial construction process, the processes during construction, deadlines, costs and use should become more efficient and easier to calculate. It is therefore only logical to integrate the costs during the entire development process.
    
Based on the 3D model, the equipment features and qualities are defined in the planning process as they are in sampling. When using the software (which is currently in use at Gruner AG) in general planning, the volume model of internal or external planning is input via an IFC interface. In the process, information such as material thickness and specifications can be imported while drawing the model. This means that the number of elements with the same qualities can be aggregated and given one cost value. The information thus obtained from the model serves as the basis for cost calculation.

Dimension time factor

Cost planning consists of the components dimension and specific cost characteristics. While the allocation of the cost characteristics requires a profound knowledge of the processor, the determination of the associated areas and volumes is usually uncomplicated. It is therefore all the more annoying that creation of a comprehensive dimension reading takes up more time during conventional cost planning than the allocation of the specific cost characteristics.

Because of the automatic adoption of the model quantities, the BIM method results in significant time savings.

Precise, transparent and up-to-date

You can use this process to react more quickly to planning changes, since the information of the previous model can already be accessed when the changed model is imported, and only the current model components need to be worked on. Variants can be analyzed with the respective cost planning in terms of their impact on the project and thus provide a basis for decision making with verifiable calculated values. An early-stage planning control over the costs can therefore be done more quickly by contrasting variants and comparing benchmarks from comparable planning.

Another trend-setting feature of the interface to the tendering process is the possibility of linking the cost values with the standard item catalog NPK, which together with the quantity calculation from the 3D model can be used as a direct basis for devising the product.

The initial experiences with this software in general planning are promising. The communication between the planners is optimized and cost certainty is increased. At the same time, it is possible to react more quickly to changes or variant studies and the considerations from cost planning can be used specifically in the tender. All in all, this is a positive development, which can be integrated into the accustomed process after some restructuring and which contributes to transparent cost planning.

What needs to be considered?

BIM is not a magical tool and does not provide cost certainty, at least not on its own. As always in the planning process, the deciding factor is those involved in the planning. If elements are forgotten in the building data modeling, they will not automatically be included in the costs. If materials are not adapted to the desired quality of workmanship, perhaps because they were not precisely defined in an earlier stage, this may be reflected in a cost estimate that is too low. Local price differences are not taken into account if this is not valued and the system is blindly trusted. The planning is only as good as the cost planner, not the software. With BIM, too, responsibility remains with the planning team, including the developer. The individual stays in the foreground but has a tried and tested aid for constructive support.

Advantages

  • query of all cost-relevant data and amounts
  • query of the completeness of definitions and sampling of building components
  • visually comprehensible presentation of the costs for the developer
  • simplified interdisciplinary cost control
  • precise cost estimates
  • continuous up-to-date cost control
  • reduced risk through higher cost certainty