# BIM Fundamentals and Level of Development Building Information Modelling (BIM) is a digital process for creating, managing, and exchanging building information throughout the project lifecycle. BIM integrates geometric models with non-geometric data — material properties, cost data, programme information, and performance specifications — into a structured, shared digital representation of the building. For the practicing architect, BIM is simultaneously a design tool, a coordination platform, a documentation system, and a data management framework. --- ## Table of Contents - [Definition and Dimensions of BIM](#definition-and-dimensions-of-bim) - [BIM Maturity Levels](#bim-maturity-levels) - [Level of Development LOD](#level-of-development-lod) - [Level of Information Need](#level-of-information-need) - [ISO 19650 Framework](#iso-19650-framework) - [Common Data Environment](#common-data-environment) - [BIM Uses by Project Stage](#bim-uses-by-project-stage) - [Clash Detection and Coordination](#clash-detection-and-coordination) - [Employer Information Requirements](#employer-information-requirements) - [BIM Execution Plan](#bim-execution-plan) - [Practical Implementation](#practical-implementation) - [See Also](#see-also) --- ## Definition and Dimensions of BIM BIM extends beyond three-dimensional modelling through additional data dimensions: | Dimension | Content | Application | |-----------|---------|-------------| | **3D** | Geometric model | Spatial coordination, visualisation, design review | | **4D** | Time/programme | Construction sequencing, phasing simulation, progress monitoring | | **5D** | Cost | Quantity extraction, cost estimation, value engineering | | **6D** | Sustainability | Energy analysis, lifecycle assessment, environmental simulation | | **7D** | Facility management | Asset data, maintenance schedules, space management | The core principle of BIM is that all project stakeholders work from a single, coordinated digital representation rather than producing independent, potentially conflicting 2D drawings. --- ## BIM Maturity Levels The UK BIM Framework (originally the Bew-Richards wedge diagram) defines maturity levels: | Level | Description | Typical Tools | Collaboration | |-------|-------------|---------------|---------------| | **Level 0** | Unmanaged 2D CAD | AutoCAD, manual drawing | Paper-based exchange | | **Level 1** | Managed 2D/3D CAD with file-based collaboration | AutoCAD, SketchUp | Shared file server; limited coordination | | **Level 2** | Federated BIM — separate models, shared via CDE | Revit, ArchiCAD, Tekla | Common Data Environment; clash detection; ISO 19650 | | **Level 3** | Fully integrated single model; open data | Cloud-based platforms, IFC | Real-time collaboration; digital twin; lifecycle data | **UK mandate**: BIM Level 2 has been mandated on centrally procured UK government projects since 2016. ISO 19650 has since replaced the Level 2 terminology with a process-based framework. --- ## Level of Development (LOD) LOD defines the reliability and completeness of model elements at each project stage. The AIA/BIMForum LOD Specification is the most widely referenced framework: | LOD | Geometric Detail | Information Content | Typical Stage | |-----|-----------------|--------------------|-| | **LOD 100** | Conceptual — massing, area, volume | Approximate parameters | Concept/Feasibility | | **LOD 200** | Approximate geometry — generic placeholders | Generic system types; approximate dimensions | Schematic/Concept Design | | **LOD 300** | Precise geometry — specific elements | Specific systems; accurate dimensions, materials | Spatial Coordination | | **LOD 350** | Precise geometry with connections and interfaces | Clash-resolution-ready; coordination elements | Technical Design | | **LOD 400** | Fabrication-ready detail | Shop drawing level; manufacturing data | Manufacturing | | **LOD 500** | As-built verified | Field-verified geometry and data | Handover/FM | **Common misconception**: LOD does not apply uniformly to the entire model. Different elements reach different LODs at different project stages. A structural column may be LOD 300 while a furniture item remains LOD 200 in the same model. **Important distinction**: LOD refers to *Development* (the degree to which the element can be relied upon), not *Detail* (visual resolution). An element can be graphically detailed but unreliable (not yet coordinated), or graphically simple but fully specified and coordinated. --- ## Level of Information Need ISO 19650 and UK guidance have shifted from LOD toward *Level of Information Need* — a more flexible framework that specifies, for each element at each stage: - **Geometrical information**: The dimensional accuracy and detail required - **Alphanumeric information**: The data attributes required (material, manufacturer, fire rating, U-value, cost, etc.) - **Documentation**: Supporting documents required (datasheets, test certificates, warranties) This approach avoids the rigidity of LOD definitions and allows project-specific tailoring. The appointing party specifies information requirements; the appointed party delivers to those requirements. --- ## ISO 19650 Framework ISO 19650 (*Organisation and digitisation of information about buildings and civil engineering works, including building information modelling*) is the international standard for BIM information management: | Part | Title | Content | |------|-------|---------| | **19650-1** | Concepts and principles | Terminology, information management concepts | | **19650-2** | Delivery phase | Information management during design and construction | | **19650-3** | Operational phase | Information management during asset operation | | **19650-5** | Security-minded approach | Information security within BIM | Key concepts: - **Appointing party**: The organisation commissioning the work (client) - **Appointed party**: The organisation delivering the work (architect, engineer, contractor) - **OIR**: Organisational Information Requirements (client's overarching data needs) - **AIR**: Asset Information Requirements (data needed for ongoing asset management) - **EIR**: Exchange Information Requirements (data required at each project stage) - **BEP**: BIM Execution Plan (the team's response to the EIR) --- ## Common Data Environment The CDE is the single source of truth for project information. ISO 19650 defines four CDE status zones: | Status | Code | Purpose | |--------|------|---------| | **Work in Progress** | S0 | Author's working area; visible only to the authoring team | | **Shared** | S1-S4 | Information shared for coordination, review, or comment; not yet approved | | **Published** | A1-Ax | Approved information issued for use | | **Archive** | | Historical record of superseded information | CDE platforms include: Autodesk Construction Cloud, Bentley ProjectWise, Viewpoint, Aconex, Trimble Connect, SharePoint (with appropriate protocols). --- ## BIM Uses by Project Stage | Project Stage | BIM Uses | |---------------|----------| | **Stage 0-1** ([[RIBA Plan of Work]]) | Existing conditions modelling, site analysis, massing studies | | **Stage 2** | Design options analysis, energy modelling, cost estimation, client visualisation | | **Stage 3** | Spatial coordination, clash detection, design freeze | | **Stage 4** | Quantity extraction, specification linking, detail development, regulatory compliance checking | | **Stage 5** | 4D construction simulation, progress monitoring, digital fabrication data | | **Stage 6-7** | As-built model, COBie data delivery, FM handover, digital twin operation | --- ## Clash Detection and Coordination Clash detection is one of BIM's highest-value applications. Federated models (combining architectural, structural, and MEP discipline models) are checked for spatial conflicts: | Clash Type | Description | Example | |------------|-------------|---------| | **Hard clash** | Physical intersection of elements | Duct running through a beam | | **Soft clash** | Clearance violation | Insufficient maintenance access around equipment | | **4D clash** | Temporal conflict | Two trades scheduled in the same space simultaneously | Coordination workflows: 1. Each discipline authors their model independently 2. Models are federated in coordination software (Navisworks, Solibri, BIMcollab) 3. Automated clash detection identifies conflicts 4. Issues are assigned, tracked, and resolved via BCF (BIM Collaboration Format) 5. Resolved models are re-checked until clashes are eliminated --- ## Employer Information Requirements The EIR (now part of the Exchange Information Requirements under ISO 19650) defines: - **Technical requirements**: Software platforms, file formats, coordinate systems, model origin - **Management requirements**: Naming conventions, CDE protocols, roles and responsibilities, information delivery schedule - **Commercial requirements**: BIM-related deliverables, model ownership, data security The EIR should be included in the procurement documents and forms part of the contractual obligations. --- ## BIM Execution Plan The BEP is the appointed team's response to the EIR. It typically includes: - Project information and team structure - BIM goals and uses - Software and hardware environment - Model management procedures (file naming, origin, units) - Information exchange schedule (what, when, to whom, at what LOD) - Collaboration procedures (CDE, clash resolution, design review) - Quality assurance/quality control procedures - Deliverables schedule --- ## Practical Implementation For practices adopting or deepening BIM: 1. **Start with standards**: Adopt ISO 19650 and CDE protocols before worrying about software features 2. **Template development**: Invest in office-standard templates, families/objects, and naming conventions 3. **Library management**: Maintain a curated library of BIM objects at appropriate LOD levels 4. **Training**: Skills in model management, clash detection, and data extraction are as important as 3D modelling 5. **Interoperability**: Use [[IFC and Open BIM]] for exchange with other disciplines when not on the same platform 6. **Quality control**: Regular model audits for compliance, file size management, and data integrity 7. **Progressive adoption**: Not every project needs full BIM; scale the approach to project complexity and client requirements --- ## See Also - [[BIM Execution Planning]] - [[BIM Collaboration and Standards]] - [[IFC and Open BIM]] - [[4D and 5D BIM]] - [[Digital Twin Technology]] - [[RIBA Plan of Work]] --- #digital #bim #lod #iso19650 #coordination