Building Information Modeling (BIM) based quantity takeoff is one of the potentially most important and profitable applications for BIM. This presentation explores the subject by presenting a case study that surveys BIM input/output dynamics for quantity takeoff, examining model behavior when constrained by existing specifications for quantity takeoff, and detailing modeling guidelines that allow the user to extract quantities according to current specifications. Takeoff specifications should therefore be revised in order to account for BIM's features, and thus minimizing its limitations.

1. Paper Study: A survey on modeling
guidelines for quantity takeoff-oriented
BIM-based design
Andre Monteiro, Joao Pocas Martins
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Advisor: Professor Wei-Chi Wang
Student: Abdoul-Aziz GANSONRE
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2.  BIM: Building Information Modeling
 QTO: Quantity TakeOff
 SIGABIM: A research project for application and implementation of
BIM.
 CRMC: Curso Sobre Regras de Medição na Construção‖ (Course on
Measurement Rules in Construction)
 LOD: Level Of Development
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3.  Introduction
 Study outline
 Research findings
 Conclusion
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4.  Quantity TakeOff (QTO) is one of the potentially most important
applications of BIM.
 Traditionally, quantity takeoff is a manual process that involves
measuring the different design elements, namely, floor
plans, elevations, cross sections and other similar documents. (error
prone: e.g. a cross section of the connection of a beam, a column, a
wall and a slab).
 This type of survey also aims to highlight the potential benefits of
using BIM for QTO.
 The following presentation will be divided will show the applications of
BIM-based QTO, its problems and recommandations.
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5. STUDY OUTLINE
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6.  QTO is one of the key tasks in the construction process.
 QTO is the measurement of the building's schematics or of the
work done on site which is assembled in a Bill of Quantities.
 QTO should be accurate because the budget of the whole
construction process depends on it.
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7. QTO applications
•Early stage: it provides the
base for a preliminary cost
estimate for the project.
• Tendering stage: it is used
to assist in the estimation of
the project's cost and
duration of the construction
activities.
•Construction stage: it is
used for the economic
control of the project.
Relation of quantity takeoff with the other major tasks in the project life-cycle.
(A. Monteiro, J. Poças Martins / Automation in Construction 35 (2013) 238–253)
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8.  BIM-based QTO provides simpler and yet more detailed and
accurate cost estimates of the project.
 Although capable of providing QTO tables, popular BIM tools
cannot manipulate that data.
 Information is usually exchanged between the BIM and cost
estimation software in one of two ways:
• Both systems use the same proprietary format for product data
definition and the exchange is done smoothly without loss of data.
• The systems use different proprietary formats and the exchange
is done by converting the data to a third, common format, usually
the Industry Foundation Classes (IFC).
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9.  ArchiCAD and Revit Architecture are the two most widely used
BIM tools for architectural design.
 Revit's QTO feature is simpler and not as powerful as
ArchiCAD's.
 ArchiCAD provides a larger choice of pre-defined
parameters, while Revit has fewer predefined measurement
parameters.
Autodesk Revit Architecture (left panel) and Graphisoft ArchiCAD (right panel) QTO parameterization interface.
(A. Monteiro, J. Poças Martins / Automation in Construction 35 (2013) 238–253)
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10.  ArchiCAD allows the user to edit some of the fields through the
definition of new configurations directly on the takeoff sheet, with such
changes being then automatically processed in the building model.
 ArchiCAD can save the tables in various formats, including Excel, PDF
and DWF. Revit only exports tables in TXT format, which often requires
further processing in order to handle the data in subsequent phases.
 There is also a number of different applications that allow the user to
perform QTO on a BIM model Vico Office, Solibri Model
Checker, Autodesk Navisworks etc.
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11.  This study was conducted under the
SIGABIM project.
SIGABIM
ArchiCAD
CRMC
LOD 300
 ArchiCAD was adopted as the BIM
tool.
 The CRMC as the criteria to be
surveyed.
 As for modeling detail, the most used
level was the LOD 300.
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12. 1/7/2014
BIM-based QTO according to the CRMC criteria survey — conceptual workflow.
(A. Monteiro, J. Poças Martins / Automation in Construction 35 (2013) 238–253)
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13.  Export to Vico Office was also taken into account in the modeling
process, meaning that no specific functions of ArchiCAD were used, thereby
preventing conflicts. The goal in SIGABIM is to use Vico Office as a tool to
extract quantities.
 Vico Office uses the same extracting engine as ArchiCAD's, which means it
will recognize the object's takeoff parameters.
 Certain CRMC criteria require greater detail in the modeling. An example of
this is would be the modeling of waterproofing finishes in roofs, where LOD
500.
 For the purpose of this article and for the sake of simplicity, the BIM design is
considered ―automatic‖ when the element ismodeled using the same
ArchiCAD element type.
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14. RESEARCH FINDINGS
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15. 1/7/2014
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16. For QTO in BIM, the coating quantities can be obtained
in 2 ways:
It can be modeled to obtain the exact quantity.
(overloaded)
It can be taken from the structural elements with a
margin of error being assumed. (errors)
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17. Issues in extracting formwork quantities from a BIM model.
(A. Monteiro, J. Poças Martins / Automation in Construction 35 (2013) 238–253)
 The formwork is not created directly from the model and there is not
even a tool for modeling formwork.
 In the IFC format, no entity is defined for formwork.
 In terms of QTO, it is not possible to obtain systematic, complete and
consistent results.
 The formwork can be measured based on the surface of the elements
involved, but this does not work where elements intersect.
 The only solution for a full and effective system is to explicitly model
the formwork, but this is extremely time consuming.
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18.  The solution found involved creating an add-on for ArchiCAD that
would automatically provide a formwork model based on the
structural model of the building.
 The add-on would use the standard ArchiCAD tools, Wall, Slab
and Roof, respectively for vertical, horizontal and sloping
formwork, to assemble the formwork model and the QTO process
would develop from there over the formwork model obtained.
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Formwork model.
(A. Monteiro, J. Poças Martins / Automation in Construction 35 (2013) 238–253)
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19.  ArchiCAD can be used to design a structural model
but it is not possible to represent the reinforced
concrete elements' rebars.
 Process: build building structure elements in a low
LOD and then export the model in a structural analysis
applicaton where the cross sections are designed and
the elements' connections detailed.
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20.  Measuring the volume of concrete is easy
because it is automatically extracted, but
grooves/recesses is difficult.
 All the grooves/recesses should be modeled
manually.
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21.  Footings, piles, beams or foundation walls, are different types of
Foundations.
 Foundations are an example of building elements which do not have a
specific modeling tool.
 Foundation elements have to be modeled using other types of elements
such as the Slab, Beam, Column, Wall.
 Each object is then associated with a specific Layer or ID in order to be
possible to isolate it from other building element types.
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22.  Stairs are rather problematic elements in that they are hard to
model and to measure.
 The ArchiCAD Stair object is quite limited in terms of QTO; their
measurement parameters are applied to the staircase object as a
whole, not to the sum of its component parts.
 The good point is that it is possible to automatically extract
quantities of the staircase.
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23.  To obtain an accurate QTO for the windows and doors, we use
the following steps:
.
1. Define and model the opening's
configurations manually, using
other ArchiCAD tools such as Wall or
Beam.
2. Model the opening using the
Window/Wall tool in ArchiCAD
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24. 3.Calculate the values
manually and add them to
the element as a label.
4. Classify the openings in
accordance with their dimensions
and other configurations, then
model and provide each opening
with a specific ID in accordance to
its classification.
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25.  The measurement of MEP elements – pipes, ducts and cableways –
cannot be achieved directly by the assessed tools.
 The average length can be taken for straight elements but not for
curved ones. In these cases, their radius and the angle of curve should
be extracted and then applied in a formula to arrive at the average
length.
 IDs and Layers should be assigned to enable the identification and
separation of the elements belonging to each continuous structure.
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26.  The SIGABIM methods presented in this article were
applied, specifically, in three projects — a hospital, an office building
and a research center.
 The overall modeling LOD 300 used in most cases proved to be
enough to satisfy the modeling and QTO needs.
 The quantities taken from ArchiCAD directly generally meet the
measurement requirements according to the demands of traditional
processes.
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27. Using BIM compared to traditional approach gives the following
benefits:
Increased accuracy in most measurements.
Direct linkage of the model extracted quantities to planning
Software.
Comparison of measurements for different phases of the
building.
Life-cycle becomes available.
Possibility of extracting partial or total quantities relating to a
given spatial area.
Margins of error often below 1%
Possibility of extracting information beyond typical
measurements, such as the number of openings or number of 27
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beams with a particular material characteristic, among others.

28.  The modeling is somewhat limited by the tools available. When it
comes to modeling — a staircase, for instance.
 As an alternative, users can configure a staircase according to their
requirements through the GDL programming function in ArchiCAD.
 Another solution would be to use elements other than the Stair tool
and assemble a staircase using Walls, Slabs and Beams.
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29. 1/7/2014
Modeling elements for QTO purposes — conceptual workflow.
(A. Monteiro, J. Poças Martins / Automation in Construction 35 (2013) 238–253)
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30. PERSONAL
REFLEXIONS
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31.  The BIM based-estimation process is not completely automatic.
 There is not a specific standard of parameterization of objects.
 Because the case study focuses on ArchiCAD, it cannot be
regarded as representative for all BIM applications.
 A quick analysis of Revit's QTO parameters and mechanics
shows that the same problems experienced with ArchiCAD are
likely to occur with Revit.?
 ArchiCAD's specific or proprietary functions often lead to errors
both in the IFC translation and in the Vico Office QTO.
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32.  About coating in the BIM tools, it is difficult to perform QTO with exact
accuracy.
 One major disadvantage of the BIM tools that were evaluated is their
inability to work with formwork in the model.
 For simplicity in this research, the BIM design is considered
―automatic‖. For manual design, the results of the present research
may not be totally relevant.
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33.  Use ArchiCAD’ GDL Programming functions to configure better
modeling and QTO parameters. (Difficult)
 Perform a survey on BIM-based QTO using Revit and see if we
encounter the same problems. Then, compare with ArchiCAD and use
some ArchiCAD QTO positive aspects to improve the QTO on Revit.
 A study on how to improve the accuracy of quantities extracted
including:
• the standardization of QTO parameters,
• the adequate BIM software and cost estimation software to use
depending on the project.
• The best ways of obtaining perfect interoperability during the extracting
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process
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34.  Monteiro, A., and Martins, J. P., (2013), “A survey on modeling guidelines for quantity takeoff-
oriented BIM-based design,” Automation in construction, Vol. 35, pp. 238-253.
 http://www.archicadwiki.com/MEP/FAQ
 http://www.abvent.com/softwares/archicad/
 http://fr.wikipedia.org/wiki/ArchiCAD
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