LOD 300 and LOD 400 are the two BIM Levels of Development most commonly conflated in proposals, scopes of work, and project execution plans. Both refer to specific, accurate model elements. Both are used on documented production projects. Both look similar in a screenshot. But they describe two completely different deliverables, and the labor difference between modeling to LOD 300 versus LOD 400 on a steel-intensive project is routinely thirty to fifty percent of the total modeling hours. Getting the LOD specification right matters — contractually, financially, and downstream.
The framework, briefly
The Level of Development framework, published by the BIMForum in the United States, defines six discrete levels: LOD 100, 200, 300, 350, 400, and 500. Each level corresponds to a specific combination of geometric accuracy, location precision, and embedded information. LOD 300 is the level most production-stage projects target as the baseline. LOD 400 is the level most steel detailing, precast detailing, and MEP fabrication scopes target as the deliverable. The two are designed to be complementary stages of a single workflow — but they specify materially different model content.
LOD 300: documented design
LOD 300 elements have accurate geometry, accurate size, accurate location, accurate quantity, and accurate orientation. Specific systems are committed: a wall has a specific wall type with specific layers, a steel beam has a specific section size, a duct has a specific diameter. The model is sufficient for construction documentation, permit submittal, contractor pricing, and inter-discipline coordination. What LOD 300 does not include: connection details, fabrication-specific information, bolt patterns, weld preparations, or any element-specific information needed for shop fabrication.
LOD 400: fabrication-ready
LOD 400 elements include everything LOD 300 includes, plus the specific information required to fabricate the element. For steel: bolt holes, weld preparations, copes, chamfers, shop notes, material specifications, fabrication tolerances. For precast: lifting points, embeds, edge details, panel-specific reinforcement. For MEP: fitting types, support locations, hanger details, fabrication spool information. The model element is sufficient for a shop to fabricate the piece directly from the model with no further design or detailing required.
Where the confusion comes from
The confusion between LOD 300 and LOD 400 usually starts with a project that needs LOD 350 — an intermediate level introduced after the original framework to capture connection and interface information without requiring full fabrication detail. Buyers who do not know LOD 350 exists often default to "LOD 400" when they actually mean "LOD 300 plus connections." This pushes the modeling labor up by thirty to fifty percent on a steel project for no downstream benefit — the fabricator does not need the LOD 400 detail because they detail in-house from the LOD 300 model and shop drawings.
The labor and cost difference
On a typical steel-intensive commercial project — say, a 300-ton steel frame with around 150 unique connections — the modeling labor breakdown looks roughly like this. LOD 300 modeling of the frame: 80 to 120 hours of senior modeling. Adding connection details to bring it to LOD 350: another 30 to 50 hours. Adding fabrication-specific information (bolt holes, weld preps, shop notes) to bring it to LOD 400: another 100 to 180 hours on top of that. The LOD 400 increment is the single largest cost step in the framework, and it should only be paid for when the downstream use of the model genuinely requires it.
When LOD 400 actually pays for itself
- Steel fabrication where the fabricator uses the BIM model directly to drive CNC equipment (KISS, NC, Fabtrol output)
- Precast manufacturing where the model drives the panel fabrication and reinforcement schedule
- MEP spool fabrication off-site where the model drives fitting cuts and assembly routing
- Modular construction where module assemblies are fabricated from the model
- Any scope where the model element will go to a shop without further detailing in between
When LOD 300 (or 350) is the right target
- Permit submittal and construction documentation
- Inter-discipline coordination and clash detection
- Steel projects where the fabricator runs their own Tekla detailing in-house and only needs LOD 300 design intent
- Multifamily and commercial projects where the structural and MEP work is field-installed rather than shop-fabricated to model precision
- Any scope where the model will be used for documentation rather than direct fabrication
Specifying LOD correctly in the BIM Execution Plan
The cleanest way to avoid the LOD 300 vs LOD 400 confusion is to specify LOD per element per phase in the BIM Execution Plan (BxP), not just per discipline. A typical BxP for a steel-intensive project might specify LOD 300 for the structural frame at construction documents phase, LOD 350 for connection coordination during shop drawing review, and LOD 400 for the structural frame at fabrication phase when the detailer takes over the model. The deliverable to the contractor stays at LOD 300; the deliverable to the fabricator moves to LOD 400. Both sets of stakeholders get what they need without the project paying for over-modeling.
The contractual implication
When a contract says "BIM at LOD 400" without further specification, the modeling team is contractually obligated to deliver fabrication-ready content on every element in the model. On a building with thousands of structural and non-structural elements, that is a substantial scope. When the same contract says "BIM at LOD 300 for the structural frame, LOD 350 for connection coordination, LOD 400 for fabrication-released steel assemblies," the modeling team can scope the work precisely and the project pays only for the LOD 400 detail on the elements that actually need it. The contractual specificity is worth the extra effort during scoping every time.
Bottom line
LOD 300 is the right target for documentation, coordination, and contractor pricing. LOD 400 is the right target for elements that go to a shop. Most projects need both, but on different elements at different phases. Specifying LOD per element per phase in the BIM Execution Plan is what separates a clean BIM contract from one where the modeling team and the owner end up arguing about what "LOD 400" actually means after the project is two months in. The framework exists to be specific — use it that way.
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