Cost Management & QTO (5D)
Quản lý chi phí & Bóc tách KL (5D)
Automatically extract material quantities from the model, attach unit rates to calculate estimates. Any design change instantly updates quantities and costs.
Common tools
Revit, Forma Takeoff, Forma Estimate
Value delivered
Stanford CIFE: BIM reduces QTO time by 80% vs. manual with greater accuracy [Source: academic]
Adoption in Vietnam
Decree 217 has NO specific 5D requirement — model-based take-off and estimating are contractual obligations that must be written into the EIR/BEP.
Level of Information Need (LOIN)
G = Geometry · A = Alphanumeric · D = Documentation (ISO 7817-1:2024 method). A blank cell means this use sets no specific requirement for that discipline/stage.
| Discipline | Concept | Schematic | Developed | Technical | As-built / Operation |
|---|---|---|---|---|---|
| Architecture | G1·A1·D0 | G2·A2·D0 | G3·A2·D1 | G3·A2·D1 | — |
| Structure | — | G2·A2·D0 | G3·A2·D1 | G3·A2·D1 | — |
| Mechanical | — | G2·A1·D0 | G3·A2·D1 | G3·A2·D1 | — |
| Electrical | — | G2·A1·D0 | G3·A2·D1 | G3·A2·D1 | — |
| Plumbing | — | G2·A1·D0 | G3·A2·D1 | G3·A2·D1 | — |
Critical stages: Concept · Schematic · Developed · Technical
Rationale: QTO / 5D costing progresses in step with design: ST1 concept cost from floor area (G1/A1, ARCH only); ST2 order-of-magnitude at LOD200 (G2/A2); ST3 reliable takeoff at LOD300 (G3/A2); ST4 variation & claim costing. A2 mandatory from ST2 for cost codes and ANZIQS/RICS NRM classification. D1 links unit-rate/spec references at detailed stages. Not used at ST5 (as-built costing uses record model, not cost_management use).
What it really is
5D Cost Management links cost data and quantity take-off directly to the BIM model so quantities are extracted automatically from model objects rather than measured by hand from 2D drawings. Each object carries base quantities (area, volume, length) and a classification code, so quantities update when the design changes. Unlike the traditional method — a surveyor measuring each drawing by hand, prone to double-counting at element interfaces — 5D rolls quantities up by classification, type and material and passes them to estimating for unit rates. The core value is not speed but auditability: every figure traces back to a specific model object.
When to use
Worthwhile for Grade II and above works (BIM mandatory under Art. 8(1)(a)), projects with large bills of quantities and frequent design changes, and large commercial or FDI projects where estimating error directly affects margins. Start only once the design model reaches a Level of Information Need (LOIN per ISO 7817-1:2024) sufficient for measurement.
Prerequisites
- •Design Authoring completed at a measurable LOIN; objects modelled as their correct types, not generic models standing in for walls, beams and columns
- •A unified classification system mapped to the Vietnamese construction norm system
- •An estimator able to read the model and configure take-off rules
- •Up-to-date norm and unit-price databases for materials, labour and plant
- •Contract or BEP defining the scope and LOIN for measurement (Art. 8(2))
Inputs
Design task team · .rvt / IFC
Appointing party · .pdf / .docx
Lead appointed party · .xlsx / .csv
Appointing party · cost task team · .xlsx
Cost task team · .xlsx
Lead appointed party · .pdf
Outputs
Auditable quantity inventory
.xlsx / xuất từ Forma Takeoff → Cost task team
Accepted when: Quantities match the model, no double counting, every line traceable to its source object
Bill of quantities by classification
.xlsx → Lead appointed party
Accepted when: Complete scope, correctly mapped to the norm system
Estimate with unit rates applied
.xlsx / xuất từ Forma Estimate → Appointing party
Accepted when: Consistent with the approved investment total and independently checked
Quantity variance report between model versions
.pdf / .xlsx → Lead appointed party
Accepted when: States the cause of each variance, not just the delta
General workflow
Prepare the model to a measurable level
Verify objects use their correct types and carry base quantities; purge generic models. One generic model that slips through becomes a wrong quantity nobody can trace later.
Design task team · Revit → Measurement-ready model
Assign classification codes
Assign a classification code to each object and map it to the Vietnamese norm system. Codes must be consistent — otherwise both the roll-up and the norm reconciliation inherit the error.
Lead appointed party · Revit · Forma Takeoff → Classified model
Extract quantities
Load the model into the take-off platform, define take-off types, roll quantities up by classification, type and material, then export the inventory with its audit trail.
Cost task team · Forma Takeoff → Auditable quantity inventory
Reconcile against the norms
Compare extracted quantities against the norm system and flag items exceeding the tolerance. A large variance rarely means the norm is wrong — usually the classification or the model is, so go back and fix it at source.
Cost task team · Forma Takeoff (.xlsx export) → Norm reconciliation sheet
Apply unit rates and build the estimate
Apply unit rates to the take-off types or pass quantities to the estimating tool. When quantities change the estimate follows, rather than being rebuilt from scratch.
Cost task team · Forma Estimate · Forma Takeoff → Cost estimate
Control change by version
Compare the new model version with the previous one, identify which quantities changed and why, and keep it on the CDE so every party works from one source instead of private spreadsheets.
Lead appointed party · Forma Data Management (CDE) → Quantity variance report
Submit the estimate for approval
Submit the estimate together with BIM data in an open format to the appointing party and the appraising authority.
Appointing party · Forma Data Management (CDE) · IFC export → Approved estimate
Diagram
↺ When the model changes, return to extraction — a 5D estimate is a living sheet, not a one-off snapshot
Common pitfalls
Extracted quantities differ sharply from manual take-off
Cause: Objects modelled as the wrong type, or double counting at element interfaces
Fix: Standardise object types and verify base quantities before measuring
Quantities cannot be mapped to the norm system
Cause: No unified classification system and no norm mapping table
Fix: Establish the classification and mapping table in the BEP before modelling starts
The estimate does not follow design changes
Cause: Take-off done in a standalone spreadsheet, disconnected from the model
Fix: Keep the model-to-take-off link and manage versions on the CDE
A quantity figure cannot be traced to its source
Cause: The quantity table carries no audit trail back to objects
Fix: Only accept quantity tables traceable to individual model objects
Parties dispute quantities with no clear right answer
Cause: The contract does not state the LOIN or the measurement rules
Fix: State the LOIN and measurement rules in the contract or BEP — Art. 8(2) assigns exactly this to the contract
Measuring effectiveness
Compare model-derived quantities with analytical calculation for the same elements: concrete, reinforcement, formwork
Benchmark: Maximum deviation of 0.75% in a peer-reviewed study of a three-storey dormitory
Compare the model-based estimate with the contractor's manually prepared bill of quantities
Benchmark: About 3.4% in the same study; the gap comes mainly from manual double counting at interfaces plus added wastage allowances
Compare cost estimating accuracy before and after adoption
Benchmark: 12% better accuracy and 18% less cost-reporting time in a study of off-site modular fabrication in Canada — a narrow context, not transferable to ordinary building projects
Compare model-based take-off time with manual take-off over the same scope
Benchmark: no independent benchmark — set an internal target
Legal basis
There is NO specific requirement for BIM-based cost management or estimating in Decree 217/2026/NĐ-CP — 5D falls under Article 8 generally. Art. 8(1)(a) makes BIM mandatory for new-build works Grade II and above; Art. 8(2) assigns scope, content and information requirements to the contract — the basis for bringing 5D into scope and setting the LOIN for measurement; at appraisal, BIM data is provided in the open IFC standard or another open format suited to the project's nature; the competent authority may additionally request the native format for cross-checking (Decree 217/2026/NĐ-CP, Art. 8(3)(a) and (b)). Requirements for quantities and estimates sit in Decree 206/2026/NĐ-CP, which only encourages BIM rather than mandating it for take-off. The practical consequence: 5D is a CONTRACTUAL obligation, not a statutory one — if you want it, write it into the EIR and BEP.
Sources
Only official sources (legislation, standards) and peer-reviewed academic work are cited. No vendor marketing figures or press sources. Reference only — does not replace legal advice.