Building Information Modeling (BIM)
Why BIM Matters for Quantity Surveyors
Building Information Modelling (BIM) has fundamentally changed how quantity surveyors work. The shift from measuring quantities off two-dimensional drawings to extracting data directly from three-dimensional digital models is the most significant change to QS practice since the profession moved from hand-written dimensions to spreadsheets. BIM does not replace the QS — it changes the tools, the workflow, and the nature of the work. The QS who understands BIM can do more, faster, and with greater accuracy than one relying solely on traditional methods. The QS who does not understand BIM will find their role increasingly constrained as clients, contractors, and design teams move to model-based delivery.
This article provides a comprehensive guide to BIM from the quantity surveying and cost management perspective — covering the policy framework that drives BIM adoption in the UK, the international standards that govern information management, the practical application of 5D BIM for cost planning and quantity extraction, the software tools available to QS professionals, and the challenges that the profession must overcome to realise BIM’s full potential. It includes a worked example comparing BIM-based quantity extraction with traditional measurement, illustrating the time and cost implications for a typical building project.
The UK BIM Mandate and Policy Framework
From Government Construction Strategy to Information Management
The UK Government’s Construction Strategy 2011 set the direction of travel: all centrally procured public sector projects would require “fully collaborative 3D BIM” by 2016. This was not an aspiration — it was a mandate. From April 2016, any project funded by central government had to be delivered at BIM Level 2 as a minimum, meaning that each discipline produced its own 3D model in a federated environment, with information exchanged using common standards and a shared data environment.
The mandate accelerated BIM adoption across UK construction. The government reported £3 billion in efficiency savings over the 2011–2015 period, driven by reduced rework, better design coordination, and more accurate cost information. The mandate also catalysed the development of the standards infrastructure — the PAS 1192 series, Uniclass 2015, the Common Data Environment concept, and ultimately the international ISO 19650 series that replaced the British PAS standards with a global framework.
The terminology has evolved. “BIM Level 2” was superseded in 2018 by the UK BIM Framework, which aligns with the ISO 19650 series and takes a more flexible, outcome-focused approach to information management. The government’s 2021 Transforming Infrastructure Performance: Roadmap to 2030 redefined the requirement as an “Information Management Mandate” — reflecting the shift from a technology specification (BIM Level 2) to an information management capability. The Construction Playbook reinforces this, requiring digital delivery and information management as standard practice on government projects.
For quantity surveyors, the practical consequence is clear: if you work on public sector projects — or for clients who follow public sector best practice — BIM is not optional. You must be able to work with digital models, extract quantities from them, contribute cost information to the common data environment, and deliver your outputs in formats that integrate with the project’s information management framework.
ISO 19650: The International Standard for Information Management
Structure and Scope
The ISO 19650 series is the international standard for managing information over the lifecycle of a built asset using BIM. It replaced the earlier British PAS 1192 series and provides the framework within which all BIM information management in the UK (and increasingly worldwide) is conducted. QS professionals must understand ISO 19650 because it defines the information requirements, delivery processes, and quality standards that govern how cost data is produced, exchanged, and managed on BIM projects.
The series comprises several parts. Part 1 (Concepts and Principles) defines the core concepts — the information delivery cycle, the Common Data Environment (CDE), status codes, and approval workflows. Part 2 (Delivery Phase) specifies how information is managed during design and construction — this is the part most relevant to QS professionals working on project delivery. Part 3 covers the operational phase (asset management). Part 5 addresses security-minded information management, relevant to defence, critical infrastructure, and sensitive projects.
Key Information Requirements
ISO 19650 introduces a hierarchy of information requirements that the QS must understand:
OIR (Organisational Information Requirements) — the client’s overarching business-level information needs. PIR (Project Information Requirements) — the specific information needed to answer the client’s questions at key decision points during the project. AIR (Asset Information Requirements) — the information needed for the operational phase. EIR (Exchange Information Requirements) — the detailed specification of what information is to be delivered, when, by whom, and to what standard. The EIR is the document that directly affects the QS — it defines the information deliverables that the cost management team must produce, the formats they must use, the level of detail required, and the delivery milestones.
The BEP (BIM Execution Plan) is the delivery team’s response to the EIR — setting out how they will meet the information requirements, what tools and processes they will use, and how they will manage quality and coordination. QS firms tendering for BIM projects must demonstrate in their BEP that they have the capability, tools, and processes to deliver cost information that meets the EIR.
5D BIM: Integrating Cost with the Model
What Is 5D BIM?
The “dimensions” of BIM describe the types of information linked to the 3D geometric model. 3D is the spatial model itself. 4D adds time (programme and sequencing). 5D adds cost — linking cost data to model elements so that the cost implications of design decisions can be understood in real time as the model develops. For quantity surveyors, 5D BIM represents the integration of cost management with the design model — the ability to extract quantities directly from the model, apply rates, generate cost plans, and track cost changes as the design evolves.
How 5D BIM Works for Cost Management
The 5D BIM workflow for a QS typically follows this sequence. The design team creates the 3D model in authoring software (typically Autodesk Revit for building projects). The QS imports the model — either the native file or an IFC export — into their cost management software. The software reads the model geometry and properties, extracting quantities (areas, volumes, lengths, counts) for each element. The QS maps these model elements to their cost breakdown structure (typically aligned to NRM 1 elements for cost planning or NRM 2 work sections for bills of quantities). Rates are applied — either from the QS’s own cost database or from benchmarking sources such as BCIS. The result is a cost plan or estimate that is directly linked to the model — when the design changes, the quantities update, and the cost impact is visible immediately.
This is a fundamentally different workflow from traditional practice. In the traditional approach, the QS measures quantities from 2D drawings — manually scaling areas from floor plans, counting items from elevations, calculating volumes from sections. This is skilled, time-consuming work that must be repeated every time the design changes. In the 5D BIM workflow, the quantities are derived from the model geometry — the QS’s role shifts from measuring to mapping, checking, and interpreting. The measurement is done by the software; the professional judgement — what to include, how to classify it, what rate to apply, what assumptions to make — remains with the QS.
Benefits for Quantity Surveyors
The benefits of 5D BIM for cost management are substantial. Speed — quantity extraction from a well-structured model is significantly faster than manual takeoff, particularly on large or complex projects. Accuracy — model-derived quantities eliminate the scaling errors, counting errors, and arithmetic mistakes inherent in manual measurement. Responsiveness — when the design changes (and designs always change), the cost plan can be updated rapidly rather than requiring complete re-measurement. Visualisation — the QS can interrogate the model visually, checking that quantities relate to the correct elements and identifying gaps or inconsistencies that would not be apparent from drawings alone. Collaboration — working from the same model as the design team creates a shared understanding of the project that improves communication and reduces the risk of misalignment between design intent and cost allowance.
IFC: The Open Standard for Data Exchange
Why IFC Matters for Quantity Surveyors
The Industry Foundation Classes (IFC) standard, published by buildingSMART International and registered as ISO 16739, is the open data format for exchanging BIM data between different software platforms. The current version is IFC 4.3, which extended the schema to cover infrastructure assets (roads, bridges, rail, ports) alongside the buildings that earlier versions addressed.
For quantity surveyors, IFC is critically important because it provides software independence. A QS using one cost management tool can receive a model created in any IFC-compliant authoring software — Revit, ArchiCAD, Bentley, Tekla, or any other — and extract quantities from it without needing the original authoring software. This interoperability is essential on projects where multiple design disciplines use different tools, and where the QS needs to work with models from different sources.
IFC files contain both the geometry (shapes, positions, spatial relationships) and the properties (materials, classifications, performance data) of each element. A well-structured IFC model allows the QS to extract not just the geometric quantities (area, volume, length) but also the descriptive information (material specification, fire rating, acoustic performance) needed to build a properly classified bill of quantities or cost plan.
Uniclass 2015 and NRM: Bridging Classification and Cost
The Classification Challenge
One of the practical challenges of BIM for cost management is mapping between the classification system used in the model and the cost breakdown structure used for cost planning. Design teams classify model elements using Uniclass 2015 — the unified classification system for the UK construction industry, compliant with ISO 12006-2. Cost plans are structured using the NRM 1 elemental breakdown. Bills of quantities are prepared using NRM 2 work sections. These are different classification systems designed for different purposes — and the QS working with BIM must bridge between them.
Uniclass 2015 was designed with this integration in mind. Its tables map to the NRM 1 elemental structure, enabling a Uniclass-classified model element to be traced to its corresponding NRM 1 cost element. This mapping is not always one-to-one — a single model element may contribute to multiple NRM elements, and a single NRM element may draw quantities from multiple model elements — but the classification framework provides the basis for systematic, repeatable mapping between the design model and the cost plan.
The QS working in a BIM environment must be fluent in both Uniclass 2015 and NRM — understanding how elements are classified in the model, how that classification relates to the NRM cost structure, and where manual interpretation is needed to bridge gaps in the mapping. This is one of the areas where the QS adds professional value that cannot be automated — the judgement to correctly allocate model-derived quantities to cost elements, taking account of what is included in each element, what is measured separately, and what requires adjustment.
BIM Software Tools for Quantity Surveyors
Model Authoring: Autodesk Revit
Autodesk Revit is the dominant BIM authoring tool for building projects in the UK. While Revit is primarily a design tool, QS professionals benefit from understanding its capabilities because it is the source of the models they work with. Revit’s built-in scheduling functionality can generate quantity schedules directly from the model — listing areas, volumes, counts, and material quantities for any category of element. These schedules provide a useful cross-check for the QS, even when dedicated cost management software is used for the formal quantity extraction.
Revit models contain rich property data — material specifications, fire ratings, thermal performance values, and Uniclass classifications — that the QS can use to inform cost allowances beyond simple geometric quantities. The quality of this property data depends on how well the model has been set up and maintained by the design team — a recurring theme in BIM for cost management.
5D BIM and Quantity Extraction: RIB CostX
RIB CostX (formerly Exactal CostX, rebranded following RIB Group’s acquisition) is one of the most widely used 5D BIM tools in UK quantity surveying practice. CostX allows the QS to import BIM models in IFC, Revit (.rvt), and Navisworks formats, and extract quantities directly from the model geometry. The software supports both 3D model-based takeoff and 2D on-screen measurement from drawings, enabling the QS to work with whatever information is available at each project stage.
CostX’s strength for QS practice is its integration of measurement with cost estimating — quantities extracted from the model feed directly into the cost estimate, with rates applied from cost libraries that can be customised to the practice’s own data. When the model is updated, the quantities can be refreshed and the cost impact of design changes identified and reported. The software also supports comparison between model versions, highlighting what has changed between design iterations — a powerful tool for managing cost during the design development process.
Model Review and Clash Detection: Autodesk Navisworks
Autodesk Navisworks is a model review and coordination tool that aggregates models from multiple disciplines into a single federated view. For QS professionals, Navisworks provides two key capabilities: visual model interrogation (navigating the combined model to understand the project scope, check for completeness, and identify potential issues) and quantification (Navisworks includes a built-in quantification module that can extract quantities from over 50 file formats). While Navisworks is not a dedicated cost management tool, its quantification features provide a useful alternative takeoff route, particularly on projects where multiple model formats must be processed.
Model Validation: Solibri
Solibri (formerly Solibri Model Checker) is a rule-based model checking and validation tool. For QS professionals, Solibri’s value lies in quality assurance — checking the model before quantities are extracted to ensure that elements are correctly classified, that there are no gaps or overlaps, and that the model is sufficiently developed for the intended purpose. Solibri’s Information Takeoff (ITO) functionality also enables extraction of material quantities, areas, and spatial data directly from the model, with outputs exportable to Excel for further analysis.
Using Solibri before quantity extraction helps the QS identify model quality issues — missing elements, incorrect classifications, duplicated geometry — that would otherwise produce inaccurate quantities. This validation step is an important part of the QS’s quality assurance process in a BIM workflow.
BIM Measurement: Causeway BIM Measure
Causeway BIM Measure is a specialist BIM takeoff tool designed for estimators and quantity surveyors. It measures directly from IFC models, DWG files, and PDF drawings within a single interface — allowing the QS to work with BIM models and traditional drawings in the same project. Features include configurable view states, 2D slicing through 3D models, automated quantity extraction, and property extraction from model elements. BIM Measure integrates with the Causeway Estimating platform, providing a seamless workflow from model-based takeoff to priced estimate.
Integrated Project Delivery: Trimble Vico Office
Trimble’s construction technology suite (including the Vico Office platform, now evolved into Tactplan for scheduling) provides an integrated 5D BIM environment covering model-based cost planning, scheduling, and production control. Vico Office links 3D model quantities to cost data and programme activities, enabling the QS to see the cost and time implications of design decisions simultaneously — a true 5D workflow. Its location-based scheduling approach is particularly powerful for repetitive structures (residential towers, hotels, student accommodation) where the same floor plate is repeated multiple times.
Quick-Reference: BIM Software for QS
| Tool | Primary QS Use | BIM Formats Supported | Key Strength |
|---|---|---|---|
| Autodesk Revit | Model authoring, quantity schedules | Native .rvt, IFC export | Industry-standard authoring tool; rich property data |
| RIB CostX | 5D BIM takeoff, cost estimating | IFC, .rvt, Navisworks | Integrated measurement and estimating; version comparison |
| Autodesk Navisworks | Model review, quantification | 50+ formats | Multi-format federation; visual coordination |
| Solibri | Model validation, ITO | IFC | Rule-based quality checking before takeoff |
| Causeway BIM Measure | BIM takeoff, estimating | IFC, DWG, PDF | Mixed BIM and 2D takeoff in single interface |
| Trimble (Vico/Tactplan) | 5D cost planning, scheduling | IFC, multiple | Integrated cost, time, and location-based planning |
For a broader overview of digital measurement tools including laser scanning, drone surveying, and GIS, see our article on Digital Tools for Measurement in the Built Environment.
Worked Example: BIM-Based Quantity Extraction vs Traditional Measurement
The Project
Consider a typical UK commercial office building — a new-build, four-storey steel-framed office of 4,000 m² gross internal floor area (GIFA), procured under a JCT Design and Build contract. The QS is preparing an NRM 1 cost plan at RIBA Stage 3 (Spatial Coordination). The design team has produced a Revit model developed to LOD 300, with all major building elements modelled geometrically and classified using Uniclass 2015.
Traditional Measurement Approach
Under the traditional approach, the QS receives 2D drawings (plans, sections, elevations) exported from the Revit model as PDFs. The QS measures each NRM 1 element manually — scaling floor areas from plans, measuring external wall areas from elevations, counting windows and doors, calculating roof areas, and deriving quantities for substructure, frame, upper floors, stairs, internal walls, finishes, and services from the drawing set. For a 4,000 m² office building at RIBA Stage 3, a competent QS would typically require 5 to 7 working days to complete the measurement and prepare the cost plan.
BIM-Based Approach
Under the BIM approach, the QS imports the Revit model (or an IFC export) into their 5D BIM software. The software extracts quantities for each modelled element — floor areas, wall areas, structural steel tonnage, window counts, door counts, roof areas, and so on — automatically from the model geometry. The QS maps these quantities to NRM 1 elements, reviews them for completeness (checking for elements that may not be modelled, such as services or below-ground drainage, that require manual allowances), and applies rates. For the same 4,000 m² project, the measurement and cost planning process using BIM typically requires 2 to 3 working days — a reduction of approximately 50 to 60 per cent in measurement time.
Cost Comparison
| Activity | Traditional Approach | BIM Approach | Saving |
|---|---|---|---|
| Quantity measurement | 4–5 days | 1–1.5 days | ~65% |
| Mapping and rate application | 1–2 days | 1–1.5 days | ~25% |
| Total cost plan preparation | 5–7 days | 2–3 days | ~55% |
| QS fee (at £450/day) | £2,250–£3,150 | £900–£1,350 | £1,350–£1,800 |
Design Change Impact
The time saving becomes more significant when design changes are factored in. On a typical project, the design will undergo several iterations between RIBA Stages 2 and 4, each requiring the cost plan to be updated. Under the traditional approach, each design change may require substantial re-measurement — if the floor plate changes, the QS must re-measure floor areas, external wall areas, window quantities, and all related elements. Under the BIM approach, the QS imports the updated model, refreshes the quantity extraction, and the software identifies what has changed. The cost plan update that takes 2 to 3 days traditionally may take half a day with BIM — and the QS can see exactly which elements have changed and by how much.
| Scenario | Traditional Time | BIM Time | Saving per Iteration |
|---|---|---|---|
| Initial cost plan (Stage 3) | 6 days | 2.5 days | 3.5 days (£1,575) |
| Design update 1 | 3 days | 0.5 days | 2.5 days (£1,125) |
| Design update 2 | 3 days | 0.5 days | 2.5 days (£1,125) |
| Design update 3 | 2 days | 0.5 days | 1.5 days (£675) |
| Total across project | 14 days | 4 days | 10 days (£4,500) |
On a single project, the BIM approach saves approximately £4,500 in QS fee time for cost planning alone. Across a practice handling 20 to 30 projects per year, the cumulative saving is substantial — and this is before accounting for the improved accuracy and reduced risk of measurement error that BIM provides.
Level of Development: What Can You Measure and When?
Understanding LOD
A critical concept for QS professionals working with BIM is the Level of Development (LOD) — which defines how much geometric detail and property information is present in a model element at each project stage. The LOD determines what quantities the QS can reliably extract from the model and what must still be estimated or measured from other sources.
LOD 100 — conceptual: the element is represented as a generic placeholder (e.g. a mass indicating the building volume). Suitable for order-of-cost estimates using £/m² rates. LOD 200 — approximate geometry: the element has approximate size, shape, and location. Suitable for elemental cost plans with approximate quantities. LOD 300 — precise geometry: the element is modelled to its actual size, shape, and position. Suitable for detailed measurement and cost planning. LOD 350 — construction detail: the element includes interfaces and connections with adjacent elements. Suitable for bills of quantities preparation. LOD 400 — fabrication: the element is modelled with sufficient detail for fabrication or construction. Suitable for contractor pricing and procurement.
The QS must verify the LOD of the model they are working with and adjust their approach accordingly. Extracting detailed quantities from a LOD 200 model will produce unreliable results — the geometry is not sufficiently developed for detailed measurement. Conversely, waiting for LOD 400 before starting cost work means the QS is not contributing to early-stage decisions when cost advice is most valuable. The skill is matching the measurement approach to the model maturity — using appropriate methods and allowances at each stage.
Challenges and Barriers for QS Adoption
Model Quality and Reliability
The quality of BIM-derived quantities depends entirely on the quality of the model. If elements are missing from the model, the quantities will be incomplete. If elements are incorrectly classified, the mapping to NRM elements will be wrong. If geometry is approximate when it should be precise, the quantities will be inaccurate. The QS cannot simply accept model-derived quantities at face value — they must check, validate, and supplement them using professional judgement. This is not a weakness of BIM; it is the same quality assurance discipline that applies to any measurement source.
Classification Inconsistencies
Despite the availability of Uniclass 2015 and its mapping to NRM, inconsistencies between model classification and cost classification remain a practical challenge. Design teams may not classify elements consistently, may use non-standard classifications, or may not classify elements at all. The QS must then manually identify and classify elements — a process that can be more time-consuming than working from well-annotated 2D drawings. Clear EIR requirements and early engagement between the QS and design team are essential to mitigate this issue.
Software Interoperability
While IFC provides an open standard for data exchange, the practical reality is that information loss can occur when models are exported from one software platform and imported into another. Properties may not translate correctly, geometric precision may be reduced, and classification data may be lost or reformatted. The QS should test the IFC export/import workflow early in the project and identify any data gaps that need to be addressed — either through improved export settings or manual supplementation.
The Skills Gap
Research consistently identifies a skills gap in BIM capability within the QS profession. Many practising quantity surveyors were trained in an era when measurement was entirely 2D-based, and their firms may not have invested in BIM training or software. Academic programmes have been slow to integrate BIM into QS curricula, and graduates entering the profession may have theoretical knowledge of BIM but limited practical experience of model-based cost management. Addressing this gap requires investment in continuing professional development, mentoring, and hands-on experience with BIM tools. The RICS BIM for Cost Managers guidance provides a starting point for structured professional development.
Cost of Adoption
BIM software licences, hardware upgrades, and training represent a significant investment — particularly for small and medium-sized QS practices. A single seat of CostX or similar 5D BIM software may cost £3,000 to £8,000 per year, and training a QS to proficiency takes time that would otherwise be spent on fee-earning work. The return on investment is real — as the worked example above demonstrates — but it requires upfront commitment and a pipeline of BIM-enabled projects to justify the expenditure.
COBie and Asset Data Handover
What COBie Means for QS
The Construction Operations Building Information Exchange (COBie) is a standardised format for capturing and handing over asset data from the construction phase to the operational phase. COBie 2.4 is the current version used on UK projects (specified in the ISO 19650-4 UK National Annex). While COBie is primarily a facilities management tool, it has relevance for QS professionals involved in whole-life costing and asset management — the data captured in COBie (equipment schedules, warranties, maintenance intervals, replacement cycles) feeds directly into the lifecycle cost models that QS professionals prepare using NRM 3.
For QS firms expanding into facilities management cost consultancy, understanding COBie and its relationship to lifecycle costing is increasingly important — particularly on public sector projects where whole-life value is a key procurement criterion, as reinforced by the Construction Playbook and the BS ISO 15686-5 lifecycle costing standard. For more on whole-life costing and the QS role in sustainability, see our article on Sustainability and Quantity Surveying.
RICS Professional Standards and BIM
What the RICS Expects
The RICS has published specific guidance for cost managers working with BIM. The BIM for Cost Managers: Requirements from the BIM Model guidance note sets out the requirements for extracting information from BIM models for cost management purposes — covering model quality expectations, the information requirements that the cost manager should specify in the EIR, and the processes for validating model-derived quantities.
The NRM suite itself is progressively being aligned with BIM workflows. NRM 1’s elemental structure maps to Uniclass 2015, enabling model-based cost planning. NRM 2’s work section structure provides the basis for preparing bills of quantities from model-derived quantities, though the mapping from model elements to NRM 2 work items still requires professional interpretation by the QS. As the RICS continues to update its standards, further integration between NRM and digital classification systems can be expected. For a detailed guide to the NRM suite and other measurement standards, see our article on Methods of Measurement in Construction.
The Changing Role of the QS
From Measurer to Analyst
BIM does not eliminate the need for quantity surveyors — it changes what they do. The time previously spent on manual measurement is freed up for higher-value activities: cost analysis, value engineering, risk assessment, options appraisal, and strategic cost advice. The QS who can extract quantities from a model in a day rather than a week has four additional days to spend on the analysis and advice that clients value most.
This shift requires a different skill set. The BIM-capable QS must understand 3D modelling concepts, classification systems, IFC data structures, and the capabilities and limitations of 5D BIM software — alongside the traditional skills of measurement, estimating, and commercial management. The profession is not losing its technical foundation; it is adding a digital layer on top of it.
For QS professionals at the start of their careers, BIM competence is no longer a differentiator — it is a baseline expectation. For established practitioners, investing in BIM skills is an investment in continued relevance. The projects are moving to BIM; the QS must move with them.
What Comes Next
This article has provided an overview of BIM from the quantity surveying perspective — covering the policy framework, standards, tools, and practical workflow for 5D BIM cost management. Future articles on ProQS.site will explore specific topics in greater depth, including practical guides to setting up 5D BIM workflows in CostX and Navisworks, a detailed look at IFC data structures for cost management, and guidance on writing BIM-related EIR requirements from the QS perspective. As the industry’s digital maturity continues to develop, the QS profession must develop with it — and ProQS.site will continue to provide the practical guidance to support that development.