LOD 200 vs 300 vs 400: Choosing the Right Revit Model Detail

Posted 28/09/2026

News

Most scan-to-BIM briefs we receive ask for “LOD 300”. Few specify what the model will be used for. That gap is where budgets get wasted and models fail downstream.

This guide is for architects, BIM managers and FM leads who want to specify existing condition models properly.

LOD is not what most people think it is

LOD, as defined in the BIMForum LOD Specification, stands for Level of Development. It describes how reliable an element’s geometry and information are for decision making. It was written for design models, where elements evolve from concept to fabrication.

An existing building is different. The walls already exist. The question isn’t how developed the design is, it’s how faithfully the model represents what was captured. That’s why LOD alone is an incomplete specification for scan to BIM.

The three levels in practice

LOD 200: generic and approximate

Elements are placeholders with approximate size, shape and location. A wall is a wall of roughly the right thickness in roughly the right place. Suitable for massing studies, early feasibility and space planning where a few centimetres don’t change the decision.

LOD 300: specific and measurable

Geometry is accurate enough to take dimensions directly from the model. Wall build-ups are represented at overall thickness, openings are correctly sized and positioned, levels are true. This is the right target for most refurbishment, planning and design development work.

LOD 400: fabrication ready

Elements carry the detail needed for manufacture and installation: connections, fixings, assemblies. For existing buildings, this is rarely justified across a whole model. It becomes relevant locally, for example, a steel frame where new members will connect to existing, or a plant room where prefabricated modules must fit the first time.

A useful rule: specify LOD per element category and per zone, not per project. A plant room at LOD 400 inside a building otherwise modelled at LOD 300 is common and sensible.

The missing piece: Level of Accuracy

LOD tells you what is modelled. It says nothing about how closely it matches reality. For that you need a Level of Accuracy (LOA) specification. The USIBD LOA framework is widely used and defines bands at a stated confidence level:

LOA	Tolerance range	Typical use
LOA10	greater than 50mm	Massing, feasibility
LOA20	15mm to 50mm	Space planning, general arrangement
LOA30	5mm to 15mm	Design development, refurbishment
LOA40	1mm to 5mm	Structural interfaces, prefabrication
LOA50	0mm to 1mm	Specialist and heritage detail

Crucially, LOA should be stated twice: once for the measured data (the point cloud) and once for the represented data (the Revit model). A point cloud captured at LOA40 can still produce a model at LOA20 if the modeller straightens every wall and flattens every floor.

Where Revit forces compromises

Revit is a design tool built for orthogonal, ideal geometry. Real buildings aren’t. Every scan to BIM model involves decisions like these:

Out of plumb walls. A wall leaning 30mm over its height can be modelled vertical at its mean position, as a slanted wall, or as an in place element. Each choice has consequences for scheduling, tagging and later editing.
Undulating floors. Slabs can deflect 20mm or more across a span. Modelling them flat is usually fine for planning. For a floor finish contractor or raised access floor designer, it isn’t.
Non orthogonal geometry. Rooms that are a degree or two out of square cause cumulative error if the modeller “tidies” them onto a grid.
Hidden elements. Anything the scanner didn’t see (inside walls, above ceilings) is inferred. Good practice is to flag inferred geometry with a parameter so users know what was measured and what was assumed.

None of these are errors if they’re agreed up front. They become errors when nobody decided.

How to specify it properly

A strong scan to BIM brief should state:

Model use. Planning drawings, design development, clash detection, FM asset register, or fabrication. Everything else follows from this.
LOD by category. For example: architecture LOD 300, structure LOD 300, MEP LOD 200, plant room LOD 350.
LOA for measured and represented data. For example: point cloud LOA40, model LOA30 for primary structure, LOA20 elsewhere.
Modelling tolerance rule. For example: “Elements deviating more than 15mm from the point cloud to be modelled to true geometry, otherwise modelled at mean position.”
Verification method. A cloud to model deviation analysis, typically shown as a colour heat map, proves the represented accuracy rather than just claiming it.
Information requirements. Under ISO 19650 and BS EN 17412 Part 1, geometry is only one part of the Level of Information Need. Define the parameters you need too, such as fire rating, material or asset ID.

Cost versus value

Moving from LOD 200 to LOD 300 typically adds meaningful modelling time. Moving to LOD 400 across a full building can multiply it. The same applies to accuracy: tightening represented tolerance from LOA20 to LOA30 means modelling real deviations rather than idealising them.

The goal isn’t the highest LOD. It’s the lowest specification that fully supports the decisions the model must inform.

Summary

Ask for LOD 300 by default, but never on its own. Pair it with LOA, define it per zone and category, and require a deviation report. That turns “a Revit model” into a deliverable you can actually rely on.

Planning a refurbishment or design project on an existing building? See our scan to BIM services to discuss the right specification for your model, or if you are looking for a full measured building survey for full property data.