PM-4 Quantity take-off from the IFC model

Business needs:

Enables the use of a neutral BIM (building information model) for cost estimation and calculation processes across the boundaries of proprietary software solutions. It should allow project teams to collaborate while using CAD and cost estimation / calculation software tools of their choice.
Cost estimations and calculations from BIM are expected to be faster, more precise, more relyable and better for optimization (recalculations of modifications and variations of the project).
One challenge of the cost estimation and quantity take-off process is, that the measurement and costing rules very depend on national and company standards. The proposed solution has to take this into account and has to allow for a configuration approach.
The proposal includes a configuration feature that allows easy customization for:

other national standards (Methods of Measurements)
company specific cost and calculation standards (e.g. many large construction companies have internal QTO instructions)
development and marketing of IFC QTO and cost catalogues

Solution:

The business process of cost estimation (early design phases) and cost calculation (late design and construction phases) has been analyzed and the following solutions are proposed:

refinement of existing IFC specifications for building element specific quantities (definition of exact generation rules for e.g. GrossFootprintArea at IfcWall)
potential additions to the quantity resource of the IFC model to exchange in addition to each quantity also:
traceable quantity generations (where does the result come from)
short and long text (specification of work items)
a configuration language for the definition of quantity calculation formula, the constraints on when to apply those rules, the substitutes, etc. This configuration language is developed as an independent XSD (XML Schema) specification.

In addition the method on how to use the configuration language and on how to implement it will be developed and prototype implementations will occur in the project.

The project uses the existing IFC specification in its current release IFC2x3 and the basic support within the extended coordination view. If additions to the IFC specifications are needed they will be proposed as part of this extension project. Most additions to the IFC specification are expected within the documentation (clear definition of basic quantities), the view definition (quantity take-off view of IFC), and the externally developed XML schema.

Scope of work:

In Scope:

The scope of the project are the agreements on the minimum set of quantities per element within the IFC specification and definition on how these quantities need to be generated and labeled. In addition an external configuration language (or catalogue) is specified that contains the formula and instructions on how to generate method of measurement specific quantities.

basic parameters and quantities (gross and net) for each building element and space element within the IFC specification and how those have to be generated
extended set of quantities for building elements and spaces (wall layer, partial space boundary) that are needed for the calculation process
configuration language to instruct the calculation of those method of measurement specific quantities (e.g. when to subtract the opening volume from the wall volume)
configuration of how to use substitute quantities (e.g. to use the net perimeter of a space object for the length of a skirting board).

Out-of scope:

national standards of measurements.

Project schedule

Project start month/year:	November 2006
Targeted completion month/year:
Process model:
Domain model:	December 2006
Pre integration:	April 2007
Integration:
Test data:	December 2007

Project team
Project leader	Chapter	Roles	Contact email
Martin Hubert	GS	I	m.hubert@dbd.de
Technical leader	Chapter	Roles	Contact email
Thomas Liebich	GS	I MSG	tl@aec3.de
Participants	Chapter	Roles	Contact email
Stefan Janke	GS	I
Rudolf Juli	GS	I
Abraham König	GS	S
Rupert Lösch	GS	I
Hans-Dieter Muntzinger	GS	S
Frank Neuberg	GS	I
Bernhard Salewski	GS	I
Raimar Scherer	GS	I
Petra von Both	GS	S

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PM-4 Quantity take-off from the IFC model

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