CDLTG · Family Authoring Reference

Lighting Family LOD

How our AL.### library tiers map to the BIMForum Level of Development Specification — so every family is authored to a known, deliberate maturity.

D5040.50 · Lighting Fixtures BIMForum LOD Spec · 2024 21-04 50 40 50 Level of Development, not Detail

Two axes, one number

The finding that reframes the whole scheme — read this before the ladder.

BIMForum defines lighting LOD on geometry and coordination only. Every grade is size, shape, spacing, location — plus the supports, seismic control, and code clearances that make an assembly coordination-ready. Read the D5040.50 rows and you will not find a single word about manufacturer, catalog number, photometrics, wattage, or dimming.

Our spec data — the real deliverable — rides a second axis the standard tracks elsewhere (AIA G202 model-element information). So AL.### commits to geometry only; spec floats above the tier, filled per project, and never sets it. A blank AL.100 symbol can end a 2D job carrying full spec data, and an accurate model with no spec is still its full geometric tier.

On the geometry axis our library tops out at an accurately-modeled AL.300 — our workhorse. AL.350 adds the field-installed coordination layer (supports, seismic restraint, clearance volumes), which is the electrical engineer's scope, not ours — so we hold it as a reserved ceiling, not an authoring target.

Geometry — the LOD axis authored range · workhorse at 300 100 200 300 350 400 authored by exception Spec / data — floats independently blank full any tier · set per project · never sets the LOD
Geometry — the AL.### / LOD axis Spec / data — floats, set per project

The tier ladder

Author to the tier's geometry; spec floats independently and never sets the tier.

100
AL.100
Conceptual Design
BIMForum D5040.50 · LOD 100
“See D50.” Fixtures aren't defined individually — the luminaire is only implied within the electrical system's generic representation.
Our geometry

A 2D symbol — nested generic annotation plus an electrical connector, if it carries one. No modeled body.

Our data / spec

Blank. Ships with no specification filled in.

Finer than the standard. BIMForum doesn't bother defining a fixture at 100; our per-fixture symbol is a deliberate library floor for 2D deliverables.

200
AL.200
Schematic Design
BIMForum D5040.50 · LOD 200
“See D5040” → “Schematic layout with approximate size, shape, and location of equipment.”
Our geometry

“2.5D” — generic modeled, hosted geometry. All round downlights share one housing/trim; distinct from the square family.

Our data / spec

Minimal. Generic type only, no manufacturer.

Clean match. “Approximate, generic equipment” is exactly BIMForum 200 — the round-vs-square split is textbook generic geometry.

300
AL.300
Design Development · workhorse
BIMForum D5040.50 · LOD 300
“Design-specified size, shape, and location of lighting fixtures; approximate allowances for spacing and clearances required for all specified hangers, supports and seismic control; access/code clearance requirements modeled.”
Our geometry

Accurately modeled to the specified luminaire at real product dimensions. No coordination geometry.

Our data / spec

Anything from blank to fully specified — spec floats and does not change the tier.

Our completed-family tier. Geometry aligns with “design-specified size, shape, and location”; we omit the hanger/seismic/clearance coordination BIMForum layers on here and completes at 350.

350
AL.350
Construction Documents · reserved ceiling
BIMForum D5040.50 · LOD 350
“Actual size, shape, spacing, and location of lighting fixtures. Actual size, shape, spacing, and location for supports and seismic control. Actual access/code clearance requirements modeled.”
Our geometry

Everything at AL.300 plus the coordination layer — supports/hangers, seismic restraint, clearance volumes — modeled as real geometry.

Our data / spec

As at AL.300 — spec is independent of the tier.

Reserved ceiling — we don't author this. The 300 → 350 gate is coordination-readiness, and that geometry is the electrical engineer's / contractor's scope. A family reaches AL.350 only if we ever produce that layer — rare, and by exception.

400
AL.400
Fabrication & Construction
BIMForum D5040.50 · LOD 400
“Supplementary components added to the model required for fabrication and field installation.”
Our geometry

Shop-drawing accurate. Custom or complex fixtures modeled as-fabricated.

Our data / spec

Full spec plus fabrication detail.

Rare, and correctly so. Catalog fixtures top out at 300 — you buy them, you don't fabricate them. Only bespoke/architectural fixtures reach 400, matching BIMForum's “fabrication” intent.

500
AL.500
As-Built · Facility Mgmt
BIMForum D5040.50 · LOD 500
Not defined in the element tables. BIMForum excludes 500 — it's a field-verified condition, about verification, not model development.
Our geometry

Field-verified actuals.

Our data / spec

As-installed record.

Not a library tier. If a family ever reaches as-built and differs from its library tier, it stays in the project only — never saved back to the shared template directory. This matches the spec's own treatment of 500.

Where we adapt the standard

Deliberate deviations — document them so the divergence stays intentional.

We stop at AL.300

supports · seismic · clearances · penetrations

The 300 → 350 gate is coordination geometry — hangers, seismic bracing, code-access clearances — the electrical engineer's and GC's scope. As a lighting design firm we don't model it, so our families top out at an accurately-modeled 300 and AL.350 is a reserved ceiling.

Spec rides a separate axis

manufacturer · catalog · photometrics · dimming

Our real deliverable is the spec, and BIMForum keeps it on a separate track. It's filled in per project and never sets the tier — an accurate model with no spec is still its full geometric tier. Keep the parameter schema constant across tiers; only fill it in further.

LOD is the authored geometric tier

AL.### = library maturity

The name commits only to the family's baked-in geometry — the axis a project can't change. Spec data floats above it per project, so a 2D CD set full of AL.100 symbols is coherent, not wrong.