If you've been involved in a BIM project, you'll have heard the term "LOD" used to describe model elements. But what does it actually mean, and more importantly, how do you know which LOD is appropriate for your project stage? Getting this wrong can mean wasting time on unnecessary detail early on, or worse, discovering during construction that your model lacks the information you need.
LOD stands for Level of Development (sometimes called Level of Detail), and it's a standardised way of describing how much geometric detail and non-geometric data a BIM element contains at any given point in a project. Understanding these levels is essential for specifying your requirements clearly, whether you're working with an internal team or outsourcing BIM modelling to a specialist provider like Outsource CAD.
What are the BIM Levels of Development?
The LOD specification was developed in the United States by the AIA (American Institute of Architects) and later refined by BIMForum. While the UK uses slightly different BIM standards overall, the LOD framework has become widely adopted internationally as a common language for describing model maturity.
There are five main levels, ranging from LOD 100 (conceptual) through to LOD 500 (as-built). Each level builds on the previous one, adding more geometric precision and embedded data as the project progresses from design through to handover.
LOD 100: Conceptual Design
At LOD 100, model elements are represented symbolically or as approximate geometric shapes. Think of basic massing models showing building volumes, or simple placeholder boxes representing major plant equipment.
This level is useful for early feasibility studies, space planning, and initial cost estimates. You're not specifying actual products or precise dimensions yet—you're establishing general concepts and spatial relationships.
LOD 200: Schematic Design
LOD 200 elements are modelled as generalised systems with approximate sizes, shapes, locations and orientations. For example, a structural steel member might be shown with correct nominal dimensions and placement, but without detailed connection information.
This level suits developed design stages where you need to coordinate disciplines and identify potential clashes between services. It provides enough information for quantity take-offs and preliminary specifications, but isn't construction-ready yet.
LOD 300: Detailed Design
At LOD 300, model elements are precisely defined in terms of quantity, size, shape, location and orientation. This is where most construction documentation begins to take shape. Specific products might be referenced, and the model contains sufficient detail for fabrication and installation coordination.
For UK engineering projects, LOD 300 is typically what's expected for BIM coordination meetings and clash detection exercises. M&E contractors reviewing coordinated services models are usually working at this level, ensuring pipework, ductwork and cable trays can be installed without conflicts.
LOD 350: Construction Documentation
LOD 350 sits between detailed design and fabrication. Elements include information about how they interface with adjacent building systems and components. Connection details, support requirements and coordination information are all included.
This level is particularly important for complex mechanical and electrical installations where interface coordination is critical. It's also the stage where specialist subcontractors typically need to be involved in model development.
LOD 400: Fabrication and Assembly
LOD 400 elements are modelled with sufficient detail for fabrication, assembly and installation. This includes precise geometry, fabrication details, connection methods and installation information.
Steel fabricators, modular plant manufacturers and specialist mechanical contractors often work at LOD 400, creating shop drawings and fabrication models. Not every project requires this level across all elements—it depends on the complexity and procurement approach.
LOD 500: As-Built and Handover
LOD 500 represents the as-built condition, verified on site. This is the final model delivered at project handover, incorporating any site variations and providing an accurate record for facilities management.
For UK building projects subject to the Building Safety Act or where structured facilities management data is required, LOD 500 models with embedded COBie data become essential handover deliverables.
Specifying the right LOD for your project stage
The key is matching LOD to project stage and intended use. There's no point commissioning LOD 400 fabrication models during RIBA Stage 3 concept design—you'll be paying for detail you don't need and can't yet define.
Similarly, trying to coordinate M&E services using LOD 200 models often fails because there isn't enough geometric accuracy to identify real clashes. Most UK coordination exercises need LOD 300 as a minimum.
When outsourcing BIM work, being clear about required LOD prevents misunderstandings and ensures you receive models fit for purpose. Experienced providers like Outsource CAD can advise on appropriate development levels for different project stages and disciplines, helping you avoid both over-modelling and under-delivery.
LOD and UK BIM standards
It's worth noting that UK BIM standards don't explicitly reference the LOD framework. Instead, UK projects typically reference the Level of Model Definition, which separates geometric detail (Level of Model Detail) from embedded data (Level of Model Information).
Despite this, the LOD terminology has become common language on UK projects, particularly those involving international teams or US-originated software. Most UK practitioners understand the LOD framework and use it alongside domestic standards.
Practical considerations for UK engineering projects
When planning BIM deliverables for oil and gas, process plant, or commercial building projects, consider which elements genuinely need high LOD and which can remain more conceptual.
Critical coordination zones—plantrooms, service risers, congested pipe racks—usually warrant LOD 300 or higher. Background elements like existing structures or out-of-scope areas can often remain at LOD 200 or even 100, keeping model sizes manageable.
Be clear in your BIM Execution Plan about LOD requirements for each discipline at each project stage. This creates accountability and ensures everyone's working to the same expectations, whether you're using in-house resources or outsourcing modelling to specialist CAD providers.
Understanding LOD isn't just technical box-ticking—it's about specifying exactly the information you need, when you need it, and avoiding paying for detail that adds no value to your particular project stage.
