Building Information Modelling (BIM) has become standard practice across UK construction and engineering projects, but one area that still causes confusion is Level of Development — commonly known as LOD. Specifying the wrong LOD can lead to wasted effort, inflated costs, or models that don't contain the information you need when you need it. Understanding what each LOD represents helps you communicate requirements clearly to your design team, whether in-house or outsourced.
This guide explains the five main LOD classifications, what they mean in practical terms, and how to choose the appropriate level for different project stages and disciplines.
What is Level of Development (LOD)?
Level of Development describes how much geometric detail and non-geometric data a BIM element contains at any given stage. It's a standardised way of defining model progression from early concept through to as-built handover.
The LOD framework was developed by the American Institute of Architects (AIA) and is widely adopted in the UK, often referenced alongside BS 1192 and the UK BIM Framework. Each LOD represents a milestone in the development of model elements, indicating both what the element looks like geometrically and what information is attached to it.
Crucially, LOD is not the same as Level of Detail (also sometimes abbreviated LOD). Level of Development includes both geometry and data, whereas Level of Detail refers only to visual representation.
LOD 100: Conceptual Design
At LOD 100, elements are represented symbolically or as generic placeholders. A wall might be shown as a simple line, or a pump represented by a basic box with approximate dimensions. There is minimal detail and the model is used primarily for spatial coordination, massing studies, or feasibility analysis.
LOD 100 is typical during RIBA Stage 1 (Preparation and Briefing) or early Stage 2 (Concept Design). It allows designers and clients to explore options quickly without committing resources to detailed modelling.
Information attached to elements at this stage is limited — perhaps just a description or broad specification. Quantities derived from LOD 100 models are indicative at best.
LOD 200: Schematic Design
LOD 200 elements are modelled as generalised systems with approximate sizes, shapes, and locations. A mechanical unit might be represented with correct overall dimensions and orientation, but without detail of internal components, flanges, or connection points.
This level is common during RIBA Stage 2 and early Stage 3 (Spatial Coordination). It's sufficient for preliminary coordination between disciplines and for identifying major clashes before detailed design begins.
Non-geometric data starts to become more meaningful at LOD 200. Elements may include performance specifications, manufacturer type, or cost estimates. Quantity take-offs are more reliable but still approximate.
LOD 300: Detailed Design
At LOD 300, elements are modelled with precise geometry, accurate size, shape, location, and orientation. Connections to other systems are defined. This is the level at which detailed coordination happens and where most clash detection takes place.
LOD 300 is typical for RIBA Stage 4 (Technical Design) and is often the minimum requirement for construction-level coordination in mechanical, electrical, and plumbing (MEP) systems. Structural steel connections, ductwork routing, and cable tray layouts are all modelled in sufficient detail for fabrication planning.
Non-geometric information is rich at this stage — specifications, product codes, installation requirements, and maintenance data. Quantity take-offs are accurate enough for final cost estimation and procurement.
LOD 350: Construction Documentation
LOD 350 sits between detailed design and fabrication. Elements include additional detail showing how they interface with other building systems or how they are supported and attached.
This level is particularly relevant for coordination-intensive projects where trades need to understand exactly how their work connects to others. MEP contractors often work at LOD 350 to ensure accurate spooling, prefabrication, and site installation.
Outsource CAD frequently delivers Revit models at LOD 350 for M&E contractors who require coordination-ready geometry ahead of fabrication. This level bridges the gap between design intent and buildable detail.
LOD 400: Fabrication and Assembly
LOD 400 elements are modelled with sufficient detail for fabrication, assembly, and installation. This includes specific assembly details, fixing methods, welds, bolts, gaskets, and support systems.
Structural steelwork detailed for fabrication, custom ductwork with seam and flange details, and bespoke joinery are all examples of LOD 400 modelling. The model becomes a direct input into manufacturing processes, often exported to CNC machines or robotic fabrication equipment.
At this level, non-geometric data includes shop drawing references, material grades, finish specifications, and installation sequences. LOD 400 models are typically produced by specialist subcontractors or fabricators rather than the main design team.
LOD 500: As-Built / As-Constructed
LOD 500 represents the facility as actually built and commissioned. It incorporates field-verified dimensions, final product selections, and any changes made during construction. This is the model handed over to the client for facilities management and future refurbishment.
Creating an accurate LOD 500 model often requires input from as-built surveys, including point cloud data from 3D laser scanning. This ensures the model reflects reality rather than design intent.
For operators in sectors like oil and gas or process manufacturing, LOD 500 models form the basis of asset registers, maintenance schedules, and digital twins. The model must include full asset tagging, warranty information, O&M manuals, and performance data.
How to Specify LOD for Your Project
The appropriate LOD depends on the project stage, discipline, and end use of the model. A common mistake is over-specifying LOD too early, which wastes time and budget on detail that will inevitably change.
For multi-discipline projects, different elements may progress at different rates. Structural elements might reach LOD 300 while services are still at LOD 200. Your BIM Execution Plan should clearly define LOD requirements for each discipline at each stage gate.
When outsourcing BIM work, clear LOD specification is essential. A good CAD partner like Outsource CAD will ask detailed questions about LOD requirements upfront to ensure deliverables match your exact needs without unnecessary over-modelling.
LOD and UK BIM Standards
While the LOD framework originates from the US, it aligns well with UK standards including BS 1192, PAS 1192-2, and ISO 19650. The UK BIM Framework emphasises information management and data drops at defined project stages, which map logically onto LOD milestones.
For publicly procured projects requiring BIM Level 2 compliance, clients typically specify minimum LOD for different disciplines at each data drop. This ensures consistency and prevents confusion across the supply chain.
It's worth noting that some UK organisations use alternative terms like "Level of Model Definition" or define bespoke detail levels. Always clarify terminology in your project contracts and BIM Execution Plan.
Final Thoughts
Understanding LOD helps you specify exactly what you need from your BIM model at each project stage — no more, no less. It's a communication tool as much as a technical standard, ensuring everyone from designers to fabricators to facilities managers speaks the same language.
Whether you're coordinating MEP systems for a commercial office, managing asset data for an industrial facility, or preparing handover documentation, getting LOD right saves time, reduces rework, and delivers models fit for their intended purpose.
