Level of Development is the most misquoted term in a BIM scope. It gets treated as a quality dial — LOD 400 must be better than LOD 300, so ask for 400 and you get a better model. That reading costs money, because the two describe different purposes, not different standards of care.
The distinction matters at the point you sign a scope. Ask for the wrong one and you either pay for fabrication-grade geometry nobody will use, or you reach the shop and find the model cannot answer the question you bought it for.
What LOD actually measures
LOD describes how much you are allowed to rely on an element, not how detailed it looks. The AIA definitions, carried into the BIMForum Level of Development Specification, are about reliability of information:
| Level | The element is | You may rely on it for |
|---|---|---|
| LOD 200 | Generic placeholder, approximate size and location | Massing, early coordination, order-of-magnitude quantities |
| LOD 300 | Specific, accurate size, shape and location | Design intent, coordination, permit drawings, takeoff |
| LOD 350 | LOD 300 plus interfaces to other trades | Multi-trade clash detection that reflects real connections |
| LOD 400 | Fabrication-ready, with assembly and installation detail | Shop drawings, fabrication, procurement of made-to-order items |
| LOD 500 | Verified as-built | Asset handover, facilities management |
A visually rich model can sit at LOD 200. A plain-looking one can sit at LOD 400. Detail in the render is not the measure.
The real difference between 300 and 400
At LOD 300, a steel beam is the right section, in the right place, at the right elevation. You can measure it, schedule it, clash it against a duct, and issue a drawing from it.
At LOD 400, that same beam carries its connections: bolt patterns, plate thicknesses, weld specifications, camber, hole locations, the fabrication marks the shop will actually cut to. The geometry is now committed to how it gets built, not just what it is.
Three practical consequences follow.
Someone must own the means and methods
LOD 400 encodes decisions that usually belong to a fabricator or a specialty contractor — connection design, sequencing, tolerance. Asking a design-side modeller for LOD 400 asks them to make choices they may have no contractual right to make. This is the most common reason an LOD 400 request stalls.
The cost curve is not linear
Going from 200 to 300 is largely a matter of committing to real products and real dimensions. Going from 300 to 400 multiplies the element count: one beam becomes a beam, two end plates, twelve bolts and a weld spec. On a structural package the modelling hours between the two can differ by a factor of three or more, and the review burden rises with it.
It goes stale faster
A fabrication-level model is tied to a specific procurement decision. Change the supplier and the connection detail may change with it. LOD 400 produced too early is rework waiting to happen — which is why it is normally staged by package, after the relevant trade is appointed, rather than applied across the whole model at once.
Which one does your project need?
Work backwards from the deliverable, not from the number:
- Permit and design intent → LOD 300. Anything more is unused.
- Multi-trade clash detection → LOD 300, moving to LOD 350 for the systems that actually collide. Interfaces are where clashes live, and plain LOD 300 often models elements without the connections that cause the real conflicts.
- Quantity takeoff for a bid → LOD 300 is usually enough. See quantity takeoff for what drives accuracy more than LOD does.
- Fabrication and shop drawings → LOD 400, scoped per trade package. This is the territory of steel detailing, rebar detailing and shop drawings.
- Handover to an FM system → LOD 500 is about verified data, not geometry. Most of the value is in the asset attributes, not the shapes. See digital twin and handover data.
The most efficient scopes are mixed. A model that is LOD 300 throughout, LOD 350 at the congested interfaces, and LOD 400 only in the packages heading to a fabricator, will cost less and be more useful than a blanket "LOD 400 please".
Write it into the scope properly
An LOD number on its own is not a scope. What prevents an argument at delivery:
- LOD by element category, not by project. Structural frame at 400, architectural finishes at 300, and so on. A model element table is worth more than a paragraph.
- Who authors each level. Name the party responsible for the fabrication-level content, and when they are appointed.
- What the model is authorised for. State explicitly whether quantities, dimensions or clash results may be relied on for contract purposes.
- The stage each level is due. LOD is a milestone, not a constant.
- The exchange format. A LOD 400 model delivered as a flat IFC may lose the parametric connection data that made it LOD 400.
If your existing conditions are being captured from a laser scan, the accuracy of the survey sets a ceiling on all of this — a model cannot be more reliable than the point cloud it came from. That trade-off is covered in scan to BIM.
LOD 300 and LOD 400 — common questions.
Is LOD 400 better than LOD 300?
No. They serve different purposes. LOD 300 supports design intent, coordination and takeoff; LOD 400 supports fabrication. Requesting LOD 400 where LOD 300 would do increases cost and review effort without adding usable information.
What is LOD 350 and when do I need it?
LOD 350 is LOD 300 plus the interfaces between elements — supports, connections and penetrations. It is the level most multi-trade clash detection actually needs, because conflicts usually occur at the connections rather than in the middle of an element.
Can a whole project be delivered at LOD 400?
It can, but it is rarely economical. Fabrication-level content depends on procurement decisions, so producing it before a trade contractor is appointed risks rework. Most efficient scopes apply LOD 400 per package, staged as each trade is engaged.
Does a higher LOD mean a more detailed-looking model?
Not necessarily. LOD measures how far the information can be relied on, not visual richness. A photorealistic model can sit at LOD 200, and a visually plain model can be fully fabrication-ready at LOD 400.