Architects are not responsible for delivering LOD 400. That level belongs to fabricators and contractors. What architects own is LOD 300 — measurable geometry, verified dimensions, confirmed material assignments — produced by the end of design development. Everything before that is LOD 100–200. What comes after is someone else's model.
No Single Standard Defines What LOD Architects Must Deliver — and That's Where Most Disputes Start
Neither the BIM Forum Level of Development Specification 2024 nor AIA Contract Document G202™ prescribes a fixed LOD target per phase per discipline. Both documents establish the vocabulary — what LOD 100 through LOD 400 mean — but they deliberately leave phase-by-phase assignments to the project team, documented in the BIM Execution Plan (BEP). The Model Element Table inside the BEP is the actual standard for each project: who produces what, at what phase, for which building systems.
This is not a gap in the standard — it's intentional. Different delivery methods, contract types, and owner requirements produce genuinely different LOD needs. The problem arises when a project starts without a signed BEP that specifies those assignments explicitly. When LOD targets are ambiguous, disputes land in shop drawing review — the most expensive place to resolve them.
What Architects Are Typically Expected to Produce — Phase by Phase
The following reflects common industry practice based on BIM Forum LOD Specification 2024 patterns and AIA G202™ Model Element Table conventions. These are typical targets, not universal requirements — the BEP governs on every project.
- Schematic Design — LOD 100–200 (Architect). Massing and approximate component layout. The building form is still changing; facade rhythms, floor-to-floor heights, and system types are still being explored. Common mistake: modeling at LOD 300 before the design is stable — the most frequent form of over-modeling, because every design revision requires re-modeling fully specified geometry.
- Design Development — LOD 300 (Architect). Geometry measurable, dimensions verified, material assignments confirmed. This is the level contractors and consultants can coordinate from, and the level AIA G202™ ties to design-phase deliverables. Common mistake: delivering LOD 200 — the contractor cannot coordinate from approximate dimensions.
- Construction Documents — LOD 300, select elements to LOD 350 (Architect + Facade contractor). For facades and curtain wall systems, specific elements reach LOD 350: system interfaces — anchor locations, slab edge conditions, transitions to adjacent assemblies — resolved between architect and facade contractor before fabrication modeling begins. For a closer look at why LOD 350 exists, see LOD 300 vs LOD 400.
- Construction Administration — LOD 400–500 (Fabricator / Contractor). LOD 400 belongs to fabricators and contractors, not architects. When architects are pushed to produce LOD 400 — manufacturer components, bolt hole locations, weld plate dimensions — they take on liability and work that belongs to the fabrication team.
What Under-Modeling Costs — When LOD 200 Is Delivered Where LOD 300 Is Expected
Delivering LOD 200 elements where the contract requires LOD 300 forces the team to revisit every element: verify dimensions, reassign component types, add orientation data. That work cannot be delegated to the contractor — it's the architect's deliverable.
The downstream effects compound quickly. Contractors coordinating from a LOD 200 model cannot reliably stage work or prefabricate components — dimensions are approximate, not verified. MEP consultants cannot confirm penetration clearances. Structural engineers cannot verify load paths against approximate wall thicknesses. The result is a stack of RFIs, change orders, and schedule delays that could have been avoided if the model had been taken to LOD 300 before issuing construction documents.
What Over-Modeling Costs — When Architects Push Past LOD 300
Over-modeling during design phases is less visible than under-modeling — but it's just as expensive, and it compounds differently. Three specific failure modes show up on facade projects.
First, the model becomes slow. Large, fully detailed curtain wall systems modeled at LOD 300 during schematic design require significant computational resources to coordinate and clash-detect. BIM managers on facade projects regularly report models becoming difficult to work with after premature LOD escalation — coordination sessions slow down, file sizes balloon, and simple design iterations require extended processing time.
Second, design changes become disproportionately expensive. Shifting a facade module from 1,500mm to 1,200mm — a routine schematic revision — means re-modeling a fully specified LOD 300 curtain wall system rather than adjusting a massing element.
Third, premature LOD 300 modeling on facade systems often forces a manufacturer selection before the design is stable. The model is built around a specific panel system's dimensions and anchor constraints. Switching systems later — because the owner changes direction or a better-priced option emerges — means rebuilding the model, not revising it. For more on this failure mode, see LOD 300 vs LOD 400.
How LOD Responsibility Splits Across Disciplines on a Facade Project
On a typical facade project, LOD responsibilities divide by discipline and phase — not applied uniformly across the entire model. The common split, based on BIM Forum LOD Specification 2024 patterns and AIA G202™ practice:
- Architect: LOD 300 — envelope, architectural systems, interior layouts, and facade grid geometry.
- Structural engineer: LOD 350–400 — connections, member sizing, and anchor interface geometry.
- MEP consultants: LOD 300 for design-phase coordination; the contractor escalates to LOD 400 for prefabrication.
- Facade contractor / curtain wall specialist: LOD 400 — fabrication modeling after manufacturer selection and design freeze.
The anchor interface — where the curtain wall system meets the structural frame — sits between architect (LOD 300 facade geometry) and structural engineer (LOD 350–400 connection details). Without an explicit assignment in the BEP, this interface falls into a gap: neither party models it fully, and the conflict surfaces during shop drawing review. On unitized curtain wall systems, where the fabricator's LOD 400 model depends on accurate anchor geometry from both architect and structural engineer, clear BEP assignments at this interface matter a great deal.
Five Things a BEP LOD Clause Must Specify to Be Enforceable
A BIM Execution Plan that assigns LOD without specifying all three variables — element, phase, responsible party — creates ambiguity that becomes a dispute. Under AIA G203–2022 and ConsensusDocs 301, the BEP is a contractually binding document; vague LOD assignments undermine that binding.
For each building system covered, the LOD clause should answer:
- What element — not "facades" but "curtain wall panels," "anchor assemblies," "spandrel panels" — specific enough to be unambiguous.
- What LOD target — expressed using BIM Forum LOD Specification definitions (LOD 100, 200, 300, 350, 400), not informal descriptions.
- Who produces it — architect, structural engineer, MEP consultant, facade contractor — named specifically.
- By which milestone — end of SD, end of DD, 50% CD, permit submission — not "during design development."
- What it will be used for — coordination, permit, fabrication — because this drives LOD adequacy checks during review.
The architect typically initiates and leads the design-phase BEP; the general contractor leads the construction-phase BEP. Both documents need to be co-authored and signed by all contributing disciplines — a step many projects skip, leaving LOD assignments unenforceable even when they are documented.
Staying at LOD 100 Through Schematic Design Makes the LOD 300 Transition Cleaner
Some facade teams have restructured their workflow to maintain LOD 100 through all of schematic design — exploring panel layouts, module rhythms, and material zone configurations without committing to a specific manufacturer's component catalog. When schematic design is approved, they transition to LOD 300 documentation from a stable, coordinated base.
Kora Studio — a Revit-native facade design plugin — is built for this sequence. Kora Studio Grid Editor lets architects define panel spacing, floor-to-floor module heights, and cladding zone assignments inside Revit using formula-driven dimension fields, without linking to any manufacturer's panel catalog. The facade schedule, material assignments, and panel layout update parametrically as the design evolves — without escalating to LOD 300 before the design is stable.
When schematic design is complete, the Kora Studio LOD 100 model becomes the coordination foundation for LOD 300 construction documentation — not a throwaway file rebuilt from scratch. For how curtain wall system families and loadable panel families work in Revit, see curtain wall families and system setup in Revit.
If your team is spending design development hours re-modeling schematic decisions, the issue is LOD sequencing — not scope. Book a demo to see what a LOD 100 facade workflow looks like in Revit.
FAQ
Does an architect ever need to model to LOD 400?
In standard practice, no. Architects own the design through LOD 300. LOD 400 — which includes manufacturer part numbers, bolt hole locations, and fabrication assembly details — is the fabricator's or contractor's deliverable, produced after the design is frozen and a manufacturer is selected. Some design-build contracts or specialty consultant arrangements assign LOD 400 production to the design team, but that is a specific contractual negotiation, not the default. AIA Contract Document G202™ is designed to make this assignment explicit through the Model Element Table. For most facade projects, LOD 300 is the architect's final responsibility.
What happens if the BIM Execution Plan doesn't specify LOD?
When the BEP omits LOD assignments, teams default to informal assumptions — which rarely match across disciplines. The architect may assume LOD 300 is the CD deliverable; the contractor may expect LOD 350 for system interfaces. The mismatch surfaces during shop drawing review or construction coordination, where it generates RFIs, change orders, and schedule impact. AIA G203–2022 and ConsensusDocs 301 both require LOD assignments in the BEP for the document to be contractually enforceable.
Can architects use LOD 300 for permit submissions in all jurisdictions?
Most building departments accept permit documents derived from LOD 300 models — measurable geometry, precise dimensions, and confirmed locations are sufficient for evaluating zoning compliance, fire separation, and structural requirements. LOD 200 is generally not accepted, as dimensions remain approximate. Requirements vary by jurisdiction; confirm with the authority having jurisdiction before submitting. For more on what LOD is required at each phase, see LOD 100, 200, 300, and 400 explained.
Who decides when to escalate from LOD 300 to LOD 350 or LOD 400?
The BIM Execution Plan governs escalation timing. In practice, the BIM Manager or Coordinator monitors LOD compliance per the BEP milestones and flags when elements need to advance. The decision to escalate to LOD 350 for a facade system, for example, is triggered by the pre-fabrication coordination milestone — typically after the facade contractor is selected and before fabrication modeling begins. Escalating outside BEP milestones — because a schedule is compressed or a contractor requests it — is a common source of over-modeling on facade projects.
Is LOD 200 ever acceptable for construction documents?
LOD 200 is not appropriate for construction documents on most projects — elements carry approximate rather than verified dimensions, which creates coordination errors and cannot support permit submissions. There are narrow exceptions: background elements that will not be constructed by this contractor, systems outside the project scope, or placeholder elements formally documented in the BEP as LOD 200. Every LOD 200 element in a CD-phase model should be explicitly labeled in the BEP with a justification — otherwise it creates uncertainty for every party coordinating from the model.
