5D BIM Cost Management is divided into two main distinct groups of users, i.e. Architects & Engineers (modeled elements only) and QS & Estimators (modeled and non-modeled elements).

Architects & Engineers (modeled elements only)

All model elements come from BIM authoring software such as Revit, ArchiCAD, Tekla, etc. In this book, we will use Revit, as it is widely used and accepted in the market.

Architects & Engineers are trained in BIM authoring software. Their scope of professional service is design, not estimating. Their role is to produce drawings for authority submission, apply for permits, and produce construction drawings for builders to construct to the required standards.

Traditionally, they would issue schematic drawings to the QS to produce a budgetary cost estimate. As the design progresses, the QS refines their estimate to match the level of detail available from the designer, and advises on the options available. This conventional workflow is known as the Cost to Design approach — a back-and-forth between the QS and designer to arrive at a price acceptable to the client.

With the instant-update nature of Revit, the Design to Cost approach is made possible. The designer, with advice from the QS, uses a build-up rate (comparative rate) to price each and every model element they have designed. For example, the pad footing build-up rate would include concrete, excavation, formwork, reinforcement, etc. In this case, the designer can focus purely on their design without needing to model temporary works like formwork, while still being able to monitor the cost of their design.

Revit provides for such costs to be inserted in the element’s Type Properties panel — a good reason for designers to make full use of it.

QS & Estimator (modeled and non-modeled elements)

On the other hand, the scope of professional service for the QS & Estimator is to provide a detailed and accurate estimate. This includes direct & indirect costs, PC & Provisional sums, contingency sum, etc. Modeled elements alone are insufficient for the QS & Estimator to prepare a cost plan, cost estimate, bills of quantities, etc.

Again, there is a tendering practice between the QS and Builders, where bills of quantities are prepared in accordance with a standard method of measurement — in this case, we use ANZSMM for explanation.

To satisfy all these needs, a Workbook is introduced to streamline 5D BIM Cost Management. The Workbook is similar to a generic spreadsheet but structured to suit cost plan and bills of quantities reporting formats, i.e. a drilled-down format enabling the insertion of Elemental/Trade headings, main headings, sub-headings, descriptions, etc.

This way, both groups remain independent of each other, avoiding overlap in their scope of work, while still fostering better BIM collaboration between them, as they are all using the same BIM platform.