Model-based quantity take-off and Cost Calculation (Building Design and Construction)
Management Summary
The objective of this working group is to create IDM (Information Delivery Manual) and MVD (Model View Definition) for LoD-K 100-500 for model delivery from authoring systems into programs for cost/quantity calculation/calculation (Architectural Model→ Cost, Architectural Model→ Contractor).
Use Case Description
For model-based quantity takeoff and cost determination, building models must contain a minimum amount of information. The authoring systems should output models according to the MVD LoD-K 300, for example. On the other hand, a program can use the MVD to check whether all required properties are included. The IFC4 schema (IFC4 Add2 TC1) serves as the basis for data and information exchange and attribution.
This use case is currently being developed by the buildingSMART-Working Group Construction2 "Digital Collaboration and Data Exchange in Construction" together with Working Group "QTo & Cost Calculation".
Purpose and scope
- Quantities can be comprehensibly derived from the model
- The traceability of quantity approaches to the corresponding model is possible
- Changes to the quantity structure can be easily documented
- Updates can be incorporated more quickly and are less error-prone
- The interpretation of the model quantities becomes much more precise for the evaluating systems
- The exchange data contains cost-relevant descriptive characteristics
- Improved traceability of the quantities for service descriptions (which component quantities are contained in a service item)
Life Cycle Stages
HOAI
BIM objectives / benefits
- The quantities for the cost calculations and service descriptions can be derived directly from the model.
- All model elements contain the information required according to the respective level of detail.
- Faster determination of quantities through direct derivation from the BIM model
- Less effort for subsequent or even renewed modeling for quotation costing at construction companies
- Quantity evaluations
- Cost calculations, e.g. according to DIN 276 or standard service areas
Delimitation
- Model-based quantity and cost calculation (LoD-K 300) Construction of Buildings
- Cost calculation
- Preparation of the tender
- Architect: Basis for preliminary quotation requests
- Construction company: Quantities for quotation costing
- It's NOT a Model-based Billing
Prerequisite / framework conditions
The detailing of the model required in each case is based on the level of development for the cost calculation according to VDI 2552 Sheet 3.
| LoD-K 100 | |
|
Figure 1 Model LoD-K 100 (source: Allplan) |
Quote VDI 2552 Example of a quantity that can be determined from a cost element with LoD-K 100: planned usable area from room schedule in m2. |
| LoD-K 200 | |
|
Figure 2 Model LoD-K 200 (Source: Graphisoft) |
Quote VDI 2552 Example of a quantity that can be determined from a cost element with LoD-K 200: planned area of building plot (FBG in m2), planned gross floor area (BGF in m2), planned gross volume (in m3). |
| LoD-K 300 | |
|
Figure 3 LoD-K 300 model (source: Graphisoft)
Figure 4 LoD-K 300 model (source: Graphisoft) |
The model consists of simple rough elements, such as walls, ceilings incl. floor structures, rooms, roofs. Quote VDI 2552 Example of a quantity that can be determined from a cost element with LoD-K 300: planned exterior wall area of building in m2, planned cleaning area of building facade in m2.
|
| LoD-K 400 and LoD-K 500 | |
|
Figure 5 Model LoD-K 400/500 (Source: Graphisoft)
Figure 6 Model LoD-K 400/500 (Source: Graphisoft) |
The 400 LoD-K model contains multi-layer superstructures with detailing from a building permit application / approval planning. The 500 LoD-K model matches the modeling approaches to the model in LoD-K 400, but contains detailed construction and more information. LoD-K 400 Model elements that allow the determination of quantities of individual construction elements with classification according to 3rd level DIN 276 or comparable as well as an allocation of services according to STLB Bau or comparable. The information status of the model elements corresponds at least to the execution planning. Example of a quantity that can be determined from a cost element with LoD-K 400: planned area of a wall panel in m2,2planned cleaning area of a window in m LoD-K 500 Example of a quantity that can be determined from a cost element with LoD-K 500: created volume of a floor slab in m3, cleaned floor area in m2 |
Distinctive feature of model delivery from planner to contractor: For a calculation on the contractor's side, remodeling is required for some components, depending on their manufacture. The construction of a wall with an opening serves as an example here. Depending on the requirements, this could be constructed differently and thus calculated differently (e.g. precast element with opening, cast-in-place concrete with recess, construction from beams and columns, etc.).
Abbreviations
LoD-K (Level of Development for Cost Calculations)
Units of measure
For the processing of quantities the following units are:
|
cm² |
Square centimeter |
mh |
Meter x hour |
|
d |
Day |
md |
Meters x days |
|
dam³ |
Cubic decameter (1000m³) |
mWo |
Meters x weeks |
|
h |
Hour |
mMt |
Meters x months |
|
a |
Year |
m²d |
Square meter x days |
|
kg |
Kilogram |
m²Wo |
Square meters x weeks |
|
km |
Kilometer |
m²Mt |
Square meters x months |
|
km² |
Square kilometer |
m³d |
Cubic meters x days |
|
l |
Liter |
m³Wo |
Cubic meters x weeks |
|
cm |
Centimeter |
m³Mt |
Cubic meters x months |
|
m |
Meter |
m³km |
Cubic meters x kilometers |
|
m² |
Square meter |
Sth |
Piece x hours |
|
m³ |
Cubic meters |
Std |
Piece x days |
|
Mt |
Month |
StWo |
Piece x weeks |
|
psch |
flat rate / lump sum |
StMt |
Piece x months |
|
St |
Piece |
St/M |
Piece per month |
|
t |
Ton |
St/J |
Piece per year |
|
Wo |
Week |
tMt |
Tons x months
|
Project Group
- Haffa, Andreas (SOFTTECH AG)
- Kreienbrink, Holger (Graphisoft Deutschland GmbH)
- buildingSMART-Working Group Construction2 "Digital collaboration and data exchange in construction" and Working Group "QTo & Cost Calculation":
- The List of Group Members will follow soon.
- IFC4 support by Mirbek Bekboliev (buildingSMART Germany) and MVD expertise by Klaus Linhard (iabi).
Copyright
buildingSMART Deutschland e. V.
All dokuments are licensed as a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License
(Attribution-Non-Commercial-ShareAlike 4.0). Further information can be found at
Handling
The documents reflect the current best practice and do not claim to be complete. They should not to be understood in the sense of a generally valid recommendation or guideline from a legal point of view. The documents are intended to support appointing and appointed parties in the application of the BIM method. The documents must be adapted to the specific project requirements in each case. The examples listed do not claim to be complete. Its information is based on findings from practical experience and is accordingly to be understood as best practice and not universally applicable. Since we are in a phase in which definitions are only emerging, the publisher cannot guarantee the correctness of individual contents.
- Document Type : Use Case
- GUID : A25D8756-90B4-4322-97AD-DCE04AC695BF
- Identifier : -
- Life Cycle Stage : HOAI
- Revision : -
- Project Status : WIP
- Maturity level : Outlook
- Published on: Aug 12, 2022
- Last change: Aug 12, 2022
- Publisher: buildingSMART Germany
- Author:
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