LOCKED strongest discipline in the doc

LDD-12 · Exposed Ceiling Systems

One-line intent

The ceiling is a designed system, not exposed chaos.

Hierarchy (highest priority placed first)

Structure (PEMB frames, purlins, spine beam)
Main HVAC trunk
Branch ducts
Electrical conduit
Lighting

Routing rules

Only N–S or E–W
Only 90° intersections
No diagonal runs · No zig-zags
Round ducts only · Long straight runs · Aligned to structure
Electrical bundled · parallel runs · clean vertical drops

Open items / engineer review

Sprinkler / fire protection routing, if code-required — not in hierarchy
Communications cabling (Cat6, fiber, AV)
Plumbing vent stacks through roof — locate now
Smoke / CO detectors, security sensors — plan in
Acoustic treatment — exposed ceiling = no absorption; gym especially reverberant

Cost drivers

Ducts ~5–15% premium over residential. Electrical ~10–25% premium. Coordination: BIM/RCP designer fee $8–18K. Net premium: ~$20–35K across HVAC + electrical + coordination, baked into trade lines.

Air-gap concerns

Acoustic dead-end. Hard surfaces everywhere. Gym will echo like a high school. Add absorption to hierarchy.
Sprinklers may be code-required for 7,200 sqft mixed-use. Verify with AHJ now.
Coordination cost. Hire a GC who's done exposed-ceiling builds; budget the coordinator.
Cleaning. Plan 6–12 month vacuum regimen + tall-ladder access.
Anchor points for hooks/pull-ups/plants — designed grid in gym ceiling.

Cross-references

← Inputs from

All other LDDs (this is meta)

→ Outputs to

LDD-17 soffits as controlled exceptions

Diagram

5-layer hierarchy from structure to lighting.