LOD 300 vs LOD 350 vs LOD 400: What Consultants and Contractors Actually Need

"What LOD do you need?" is one of the first questions we ask on every new engagement, and it's usually the one people are least sure how to answer. LOD gets specified in contracts and BIM execution plans as if it's a fixed, obvious number, but in practice the difference between LOD 300, 350 and 400 comes down to one thing: what decisions does the model need to support, and who's making them?

Here's what actually changes at each level, and how to tell which one you need.

Three levels, three different jobs

LOD 300: coordinated, not constructible

At LOD 300, ductwork, pipework, cable tray and equipment are modelled with accurate size, shape, location and orientation. This is enough to run meaningful clash detection against architectural and structural models, and it's the standard level for design-development coordination — resolving whether a duct run and a structural beam are fighting for the same ceiling void, for instance.

What LOD 300 doesn't give you is real-world fabrication detail. Fittings are generic. Supports usually aren't modelled at all, or are placeholder geometry. Two systems can be shown crossing near each other without the model knowing whether they actually connect, and how.

This is the right level for a consultant running design-stage coordination, where the goal is resolving the big spatial conflicts before construction documents are issued — not yet producing something a fabrication shop could build from.

LOD 350: the interfaces start to matter

LOD 350 keeps the generic component philosophy of LOD 300 but adds one important thing: interfaces. The model now shows how a piece of ductwork connects to an air handling unit, how a branch pipe ties into a main, how a cable tray transitions between two structural bays. Components still aren't manufacturer-specific, but their relationships to each other and to other systems are explicit.

This matters most when several disciplines are converging in a tight space — a plant room, a service riser, a congested ceiling void — where knowing that two things are near each other isn't enough. You need to know whether they actually interfere at the connection point, not just along the run.

LOD 350 is often the right upgrade from LOD 300 late in design development, when a project is congested enough that generic clash detection starts missing real conflicts hiding in the connection details.

LOD 400: this is where fabrication lives

LOD 400 is a different kind of model, not just a more detailed version of LOD 350. Components become manufacturer- and product-specific: actual fitting geometry, actual support spacing and type, actual sleeve and penetration sizes, actual valve and equipment models with their real connection points and maintenance clearances.

This is the level a model needs to reach before shop drawings, spool drawings, or fabrication packages can be produced from it directly. Everything downstream — cut lists, spool numbering, support schedules — depends on the model already carrying this level of real-world accuracy. Skip straight to LOD 400 too early in design, before layouts are settled, and you'll pay for it in rework every time a system gets rerouted. Leave it too late, and fabrication gets delayed waiting on detail that should have already existed in the model.

A clash-free LOD 300 model tells you the systems don't conflict in principle. A clash-free LOD 400 model tells you they don't conflict in reality.

Why the jump from 350 to 400 is the expensive one

Going from LOD 300 to LOD 350 is mostly a modelling exercise — same components, more relationships defined between them. Going from LOD 350 to LOD 400 is a different kind of work: every generic fitting gets swapped for a real manufacturer part, every support gets sized and placed against actual load and spacing requirements, every connection gets checked against a real clearance envelope, not a generic one.

This is also where clash detection stops being a design-coordination exercise and starts being a construction-readiness one. That's the reason a clash-free sign-off only really means something once a model has reached LOD 400.

Which one do you actually need?

In practice, this tends to split cleanly along one line: are you designing, or are you building?

If you're a consulting engineer running design-stage coordination — resolving conflicts before documents are issued, still iterating on layout — LOD 300 or LOD 350 is almost always the right target. Pushing to LOD 400 before the design has settled means re-detailing the model every time something moves, which is expensive and mostly wasted effort.

If you're a contractor taking a model into procurement, fabrication and installation, LOD 400 isn't optional — it's the only level detailed enough to actually build from, and it's the level a clash-free guarantee should be measured against. Anything less, and "clash-free" is describing the design intent, not the thing that's about to get fabricated and installed.

Two tracks, not one blanket service

This is exactly why we run two different engagement tracks rather than one blanket service. Design-stage coordination for consultants is scoped to LOD 300/350, focused on resolving conflicts fast without over-detailing a layout that's still moving. Construction-ready delivery for contractors is scoped to LOD 400, with a clash-free guarantee that actually means what it says, because the model has the fabrication-level detail to back it up.

If you're not sure which side of that line your project sits on, that's a normal question to have at kickoff — it usually comes down to how settled the design is and what the model needs to produce next.