If you've been handed a BIM model or asked to specify one for your project, you've likely encountered the term "LOD" followed by a number. Level of Detail (sometimes called Level of Development) is a framework that defines how much geometric and non-geometric information is included in a BIM element at different project stages.
Getting the LOD specification right matters. Over-model too early and you'll waste time and budget on detail that may change. Under-model too late and you risk coordination clashes, procurement delays, and incomplete handover information. This guide explains what each LOD means in practical terms and how to apply it to UK construction and engineering projects.
What is Level of Detail (LOD) in BIM?
LOD is a standardised way to communicate how much information a BIM element contains at any given stage. Originally developed by the American Institute of Architects (AIA), the framework has been widely adopted internationally and aligns well with UK BIM Level 2 requirements and PAS 1192 standards.
Each LOD level—from 100 to 500—represents a progressive increase in the certainty, specificity, and detail of model geometry and attached data. The LOD you choose should match the project stage, the purpose of the model, and the decisions that need to be made at that time.
It's important to note that different elements within the same model can be at different LODs. For example, structural steelwork might be modelled at LOD 350 while mechanical plant is still at LOD 200 during early coordination stages.
LOD 100 — Conceptual Design
At LOD 100, BIM elements are represented symbolically or as simple placeholders. You might see a box representing a boiler room or a basic volume indicating a plant enclosure. There's no specific size, shape, or location detail—just an indication that something will be there.
This level is appropriate for feasibility studies, early space planning, and cost estimation based on area or volume. You wouldn't use LOD 100 for coordination or procurement, but it's a useful starting point for design development and client approvals at concept stage.
LOD 200 — Schematic Design
LOD 200 elements are modelled as generic systems with approximate sizes, shapes, and locations. A structural column might be shown with the correct rough dimensions and location, but not yet specified as a particular steel section. An air handling unit might appear as a box with approximate dimensions and major connection points.
This is the level typically used during RIBA Stage 3 (Spatial Coordination) in the UK. It's detailed enough for early coordination between disciplines, preliminary clash detection, and outline specifications. However, it's not sufficient for fabrication or detailed installation.
LOD 300 — Detailed Design
At LOD 300, elements are modelled with specific assemblies, precise dimensions, and accurate locations. A steel beam is now a specific UB section with correct orientation. Mechanical equipment is modelled with actual manufacturer sizes and connection locations. Ducts and pipes show routing and major fittings.
This is the workhorse LOD for most UK construction projects during RIBA Stage 4 (Technical Design). It provides enough detail for accurate coordination, clash detection, and construction sequencing. Contractors can use LOD 300 models for site planning and procurement of long-lead items.
Many UK M&E contractors and structural engineers work with BIM specialists like Outsource CAD at this level to ensure coordination models are accurate and clash-free before construction begins.
LOD 350 — Construction Documentation
LOD 350 sits between detailed design and fabrication. Elements include interface detail with other systems—connection points, supports, penetrations, and how components relate to adjacent elements. This level is particularly important for mechanical, electrical, and plumbing coordination.
At LOD 350, a pipework model shows not just the pipe routes but also flanges, valve orientations, support brackets, and penetrations through walls. This allows fabricators and installers to understand exactly how systems connect and what they need to coordinate on site.
This level is increasingly expected on larger UK construction projects where design responsibility passes to specialist subcontractors who need to coordinate detailed installations.
LOD 400 — Fabrication and Assembly
LOD 400 models contain enough detail for fabrication, assembly, and installation. Elements include precise dimensions, materials, connections, and fixing details. A structural steel model at LOD 400 shows bolt holes, weld details, and connection plates. A ductwork model shows seam orientations and hanger positions.
This level is typically produced by fabricators and specialist subcontractors rather than the main design team. It's used to drive CNC machines, generate shop drawings, and coordinate site installation. Not every project requires LOD 400 across all disciplines—it depends on procurement routes and contract responsibilities.
LOD 500 — As-Built and Handover
LOD 500 represents the as-built, as-constructed model verified on site. It reflects what was actually installed, including any variations from the design model. This is the model handed over to the client for facilities management and future modifications.
Under UK building regulations and increasingly in contract requirements, as-built information must be provided at project completion. For complex M&E systems and process plants, this includes not just geometry but also asset data, maintenance schedules, and warranty information embedded in the model.
Creating accurate LOD 500 models often requires survey verification using laser scanning or traditional measurement. Outsource CAD supports UK engineering firms with as-built modelling services, converting site survey data and redline markups into verified BIM models for handover and facilities management.
How to Specify LOD for Your Project
The key is to match LOD requirements to project stage and decision points. Your BIM Execution Plan (BEP) should clearly state which elements need to be at which LOD at each project milestone. This avoids confusion and ensures everyone understands what they're producing or receiving.
Consider also who is responsible for developing each LOD. Typically, consultants develop to LOD 300, specialist contractors to LOD 350 or 400, and facilities teams maintain LOD 500. Procurement routes and contract terms need to align with these expectations.
Remember that higher LOD doesn't always mean better. Developing unnecessary detail too early wastes time and creates rework when designs change. Match the LOD to the purpose, and you'll get better value from your BIM investment.
LOD and UK BIM Standards
While LOD originates from US standards, it aligns well with UK BIM Level 2 requirements under PAS 1192 and the newer ISO 19650 series. UK projects should reference LOD requirements in Employer's Information Requirements (EIR) documents and ensure the BEP addresses how LOD will progress through project stages.
The UK also uses the concept of "Level of Information" alongside Level of Detail, recognising that models contain non-geometric data as well as 3D geometry. Together, these concepts help define what "BIM Level 2 compliant" actually means in practical terms.
Working with BIM Outsourcing Partners
Many UK engineering firms outsource BIM modelling to manage workload peaks and access specialist expertise. When working with a BIM partner, clear LOD specifications in your brief ensure you receive models fit for purpose without paying for unnecessary detail.
Experienced providers understand UK standards and can advise on appropriate LOD for your project stage and objectives. Whether you need coordination models at LOD 300, detailed fabrication models at LOD 400, or as-built documentation at LOD 500, the right partner will match deliverables to your actual requirements.
Understanding LOD gives you a common language to discuss BIM requirements with your team, your clients, and your supply chain. It ensures everyone knows what they're producing, what they're receiving, and when—
