One of the most common sources of confusion on BIM projects is the question of model detail. How much information should be included at each stage? What does the client actually need at design freeze, and what can wait until construction or handover?
The answer lies in understanding Levels of Development (LOD), a standardised framework that defines how much geometric detail and non-geometric data a BIM element contains at each project phase. Getting this right can save time, reduce abortive modelling work, and ensure you're delivering exactly what's required—nothing more, nothing less.
What is Level of Development (LOD)?
Level of Development is a specification that describes the completeness and reliability of BIM elements at various stages of the design and construction process. It was originally developed in the United States by the AIA (American Institute of Architects) and has since been widely adopted internationally, including across UK projects.
LOD should not be confused with Level of Detail—a common mistake. Level of Detail refers only to how much geometry is modelled, whereas Level of Development includes both geometric detail and the associated data or information attached to that element.
The LOD framework runs from LOD 100 (conceptual) through to LOD 500 (as-built and operational), with LOD 200, 300, and 400 sitting in between. Each level represents a progressively more defined and data-rich model.
LOD 100 — Conceptual Design
At LOD 100, BIM elements are represented symbolically or as generic placeholders. You might model a plant room as a simple box with an approximate volume, or a structural column as a basic cylinder in roughly the right location.
This level is used during feasibility studies and early concept design. The focus is on massing, spatial relationships, and approximate quantities—not on specific products or construction details.
LOD 100 models are useful for cost estimating at Order of Magnitude level and for communicating high-level design intent to clients and stakeholders.
LOD 200 — Schematic Design
LOD 200 introduces approximate geometry, size, shape, and orientation. Elements are still generic, but they begin to resemble the actual components that will be installed.
For example, a structural steel column will now have the correct cross-sectional shape (I-beam, H-section, etc.) and approximate dimensions, but it won't yet specify the exact steel grade or connection details.
This level supports outline design development and is often used during RIBA Stage 3 (Spatial Coordination) in UK projects. It's sufficient for early coordination between disciplines and for producing indicative schedules and quantities.
LOD 300 — Detailed Design
LOD 300 is where BIM models become detailed enough to support fabrication and construction planning. Elements are modelled with precise geometry, accurate location, and detailed non-geometric information such as material specifications, fire ratings, and performance data.
At this level, you can coordinate services, identify clashes, and generate accurate quantities for procurement. M&E contractors will typically work to LOD 300 when coordinating ductwork, pipework, and cable trays in a plant room or riser.
Many UK projects specify LOD 300 as the deliverable standard for construction issue drawings. It strikes a balance between usability and effort, providing enough detail to build from without over-modelling elements that may still change on site.
LOD 400 — Fabrication and Assembly
LOD 400 includes all the detail needed for fabrication, assembly, and installation. This means modelling bolts, welds, supports, fixings, and shop drawing-level information.
Steel fabricators, precast concrete suppliers, and mechanical contractors working on complex plant installations often require LOD 400 models. These are used to produce shop drawings, cutting lists, and CNC machine instructions.
LOD 400 is not typically required across an entire building model—it's used selectively for specific packages or elements where precision fabrication is critical.
LOD 500 — As-Built and Operations
LOD 500 represents the as-built condition of the project. The model is updated to reflect what was actually constructed, including any design changes, site modifications, or product substitutions made during the build.
This level is used for facilities management and operations. It forms the basis for digital twins, COBie data handover, and ongoing maintenance planning. Under UK building regulations and contractual requirements, as-built information is often mandatory at project handover.
Creating and maintaining an LOD 500 model requires input from site records, as-installed surveys, and sometimes point cloud data to verify final geometry.
Choosing the Right LOD for Your Project
The key to efficient BIM delivery is specifying the correct LOD for each stage of your project and for each discipline. Over-modelling wastes time and budget; under-modelling leads to coordination problems and rework.
Your BIM Execution Plan (BEP) should clearly define LOD requirements by project stage, discipline, and element type. For example, architectural walls might be modelled to LOD 300, while a bespoke steelwork connection is taken to LOD 400 by the fabricator.
Communication between the design team, contractor, and client is essential. Everyone must understand what LOD has been specified and what that means in terms of model usability and decision-making.
How Outsource CAD Supports LOD-Specific Modelling
Many UK engineering and construction firms turn to specialist providers like Outsource CAD to develop BIM models to the appropriate LOD, particularly when internal resources are stretched or specific expertise is required.
Whether you need LOD 300 mechanical services coordination models, LOD 400 steelwork for fabrication, or LOD 500 as-built documentation from point cloud data, working with an experienced CAD and BIM partner ensures consistency, accuracy, and compliance with UK standards.
Outsource CAD works with clients across construction, oil and gas, telecoms, and M&E sectors to deliver Revit models, Navisworks coordination, and federated BIM outputs tailored to the exact LOD required at each stage.
Final Thoughts
Understanding LOD is fundamental to successful BIM project delivery. It helps you scope work accurately, manage expectations, and avoid costly over-modelling or inadequate information at critical stages.
By aligning your LOD requirements with your project programme, procurement strategy, and handover obligations, you ensure that your BIM models add value without unnecessary effort. And when you need specialist support to achieve that balance, experienced outsourcing partners are available to help you get it right.
