HVAC Duct Shop Drawings: 2025 Guide | Built In BIM

What are HVAC ductwork shop drawings?

HVAC ductwork shop drawings translate design intent into buildable, coordinated, and fabrication-ready documentation. They capture the exact routing, sizes, materials, gauges, joints, hangers, penetrations, and connections to equipment and terminals—plus the metadata needed for procurement and fabrication.

How they differ from other drawing types:

• Design drawings: Convey intent and performance (airflows, zoning). Not build-level detail.
• Coordination drawings: Resolve clashes between trades and structure.
• Shop drawings: The final, approved record of what gets fabricated and installed—often including spools and cut lists.

Typical sheets: plans by floor/zone with system color coding; sections/elevations at congested areas; isometrics for risers and complex runs; spool drawings with piece marks and BOMs.

Standards & specs you must align to (2025)

A compliant set always ties back to governing standards and the project specification.

• SMACNA: Construction standards for duct joints, seam types, reinforcement, tie-rod spacing, and hanger rules.
• ASHRAE: Airflow, pressure, velocity, and leakage class guidance that influences sizing and sealing.
• Regional standards: e.g., DW/144 for UK/EU projects.
• Project Specifications: Always override generics if more stringent. Deviations must be recorded, clouded, and approved.

Built In BIM practice: We annotate each sheet with the applicable standard, pressure class, and material notes, and we maintain a Variance Register so every exception is explicit and traceable.

HVAC Ductwork Shop Drawing Deliverables

• Title sheet, legends, abbreviations
• Color-coded plans with duct sizes, material, gauge, pressure class, insulation/lining, and airflow tags
• Sections/elevations at congestion zones with elevation bands for MEP trades
• Isometrics & spools with piece marks, joint numbering, and cut lists
• Fittings schedule using SMACNA notation (radius elbows, transitions, taps)
• Hanger & support details (rod size, spacing, attachment, trapeze, seismic notes)
• Dampers, access doors, test ports—with access clearances indicated
• Equipment connections (AHU/RTU/FCU/VAV) with flex duct limits and vibration isolation notes
• Penetration/firestopping details, sleeves, and fire/smoke zoning
• BOMs at sheet and package level; revision control with date/author stamps
• Labeling & tagging schema for traceable install and commissioning

Inputs to Start Ductwork Shop Drawings

• Latest IFC/CD drawing set, including architectural RCPs
• Project spec sections (23 31 00 etc.) for materials, gauges, leakage class
• Equipment submittals and diffuser/damper schedules
• Structural openings, sleeves, and embeds; slab/beam models if available
• Coordination rules (priority matrix), LOD targets, layer/naming conventions
• Point cloud or as-built survey (when accuracy to existing is critical)

Duct Sizing & Material Selection

• Rectangular vs. round/oval: Round often reduces leakage and pressure drop; rectangular can fit tight ceilings but may need more reinforcement.
• Materials: Galvanized for most supply/return; stainless for high-humidity or corrosive; double-wall or lined for acoustics and thermal control.
• Pressure class & gauge: Selected per standard and project spec; impacts seam type, reinforcement, and hanger spacing.
• Fire/smoke zoning: Drives damper locations, sleeve/firestop details, and access door placement.

Built in BIM note: We include a quick-reference table on the title sheet showing pressure class → typical gauge → joint type, so reviewers see the logic up front.

BIM Coordination & clash resolution

• LOD 300 → 350 → 400 milestones with defined sign-off points
• Corridor cross-sections: We freeze elevation bands by trade so ducts, pipes, trays, and sprinklers coexist predictably
• Clash categories: Structural, MEP-MEP, and architectural finishes (e.g., soffits)
• Tolerances & clearances: We model maintenance zones for dampers, coils, filters, and access panels
• RFI/change logs: Every issue gets a unique ID, status, owner, and date; approvals are traceable

Model-to-Fabrication Handoff

• Fabrication parts vs. generic families: We prefer fab-ready parts where vendor workflows require it; otherwise we map parameter sets for clean exports.
• Spooling strategy: Logical zones, floor splits, and truck/pallet constraints; each spool has a piece-marking system that installers can follow at a glance.
• Numbering & traceability: QR/barcodes on spools and BOMs link drawings ↔ parts ↔ install sequences.
• CAM/Nesting: Deliverables align to plasma/coil line inputs; we export cut lists in mutually agreed formats.

Hangers, seismic, and installation details

The difference between a neat ceiling and a change order often rests here:

• Hanger spacing: Determined by duct size, weight, and pressure class; trapeze systems used where shared supports make sense.
• Seismic bracing: We show brace locations, hardware, and anchorage concept—supported by manufacturer submittals.
• Anchors & deflection: Slab/beam anchors, allowable deflections, and vibration isolation are detailed.
• Access & maintenance: We protect access around dampers, coils, and test ports; everything that needs a wrench gets space.

Hanger spacing cheat sheet (indicative):

Final spacing per standard, gauge, and project spec.

Submittals & approvals (step-by-step)

• Pre-submittal QC: Our internal checklist ensures completeness, standards compliance, and legibility.
• First submittal: Clouded notes highlight assumptions and requested clarifications.
• A/E review & comments: We log every comment, cross-link to sheets, and respond inline.
• Resubmittal: Revisions clouded; Revision Table updated with Rev/Date/By/Description.
• Final issue (IFC/IFD): Approved set issued with distribution matrix for field, fab, and commissioning.

QA/QC Checklist for Duct Shop Drawings

• Views present: Plans, isos, sections at congestion zones
• Dimensions & levels: Centerlines, soffit clearances, slopes (if any)
• Materials/gauges: Matched to pressure class and spec; double-wall/lining shown where required
• Fittings: Within SMACNA limits; radius/transition rules observed
• Dampers & access: Access doors, test ports, and clearances shown and dimensioned
• Hangers/seismic: Rod size, spacing, trapeze details, anchors referenced to standard details
• Penetrations/firestopping: Sleeve sizes, firestop details, and UL references (where applicable)
• BOM integrity: Sheet BOMs match spools; totals reconcile
• Title blocks: Project data, sheet number, scale, revision, drawn/checked/approved stamps
• Coordination sign-offs: Structural, MEP trades, and A/E approvals captured

Cost, Timeline & Risk (HVAC Shop Drawing Projects)

Typical timelines depend on scope and drawing quality:

• Small tenant fit-out: 1–2 weeks for shops + 3–5 days approval
• Mid-rise multi-floor: 3–5 weeks for shops + 1–2 weeks approval
• Large healthcare/industrial: 6–10+ weeks staged by area

Risk reducers:

• Lock equipment submittals before shop start
• Freeze sleeve/penetrations early
• Agree on spooling and shipping sequences during coordination
• Use a single source of truth for revisions (decision register)

Value engineering levers:

• Convert long rectangular mains to round/oval to reduce reinforcement and leakage
• Prefabricate risers and repeated typologies
• Standardize hanger types and trapeze spans across floors

Common Ductwork Shop Drawing Mistakes

• Damper access not modeled → no clearance = failed inspection
• Oversized rectangular in narrow corridors → impossible elevation stack
• Uncoordinated diffuser necks vs. supplier catalog → last-minute adapters
• Missing piece marks on spools → install confusion and rework
• Ignored ceiling types (hard ceilings, feature soffits) → re-routing on site

Case snapshot (Built In BIM)

Project: 12-story mixed-use, 340,000 sq ft

Challenge: Persistent MEP clashes at corridors and shafts; late equipment submittals.

Approach: Rapid LOD 350 sections at all corridors, standardized elevation bands, weekly RFI cadence, spooling by core/floor.

Results:

• –62% clashes prior to final coordination sign-off
• –48% RFIs during construction phase
• +19% faster install for main runs (tracked via piece-mark progress)

Tools & file formats (vendor-neutral)

Authoring/coordination/viewers: Revit, AutoCAD, Navisworks, IFC viewers

Exchange formats: RVT, DWG, IFC, NWC/NWD, CSV, PDF

Versioning: Clear naming and Rev tables (e.g., BIB-HVAC-XX-FL02-SHOP-PLN-001_RevC_2025-01-18.pdf)

Why Built In BIM

• Outcome-first coordination: Field-ready drawings that pass review and install cleanly
• LOD-400 rigor: Fab-friendly spooling and traceable piece-marking
• Tool-agnostic: We fit your vendor and CAM workflows—not the other way around
• Transparent documentation: QC checklists, variance registers, decision logs
• Flexible engagement: Fast-track, surge support, and night-shift collaboration for compressed schedules

FAQ

Q: Who sizes the ducts in shop drawings?

A: Designers typically define flows and preliminary sizes. In shops, we validate against standards and constraints; where field conditions dictate change, we raise an RFI and document the accepted adjustment.

Q: How do you prove SMACNA compliance?

A: We cite the exact table/section on sheets, show joint/reinforcement types, and include a title-sheet matrix mapping pressure classes to gauges and seams. QC screenshots and calculation snippets can be appended.

Q: What makes a drawing “fabrication-ready”?

A: Fab parts (or mapped parameters), complete spools with piece marks, BOMs that reconcile, joints and seam definitions, hangers with spacing/anchors, and zero unresolved clashes.

Q: How do spools reduce site errors?

A: Each spool bundles installable segments with unique IDs that tie to BOMs and sheets. Installers follow the sequence; QA can track progress via piece-mark scans.

Q: What’s a realistic turnaround for a mid-rise?

A: Assuming stable inputs: 3–5 weeks for shops and 1–2 weeks for approval. Parallelizing by zone can compress this.

Q: How do you handle damper/access clearances?

A: We model access doors and maintenance boxes, dimension the clear space, and coordinate with ceilings/adjacent trades. Any squeeze is flagged in coordination.

Q: Can you work with our fabricator’s CAM?

A: Yes. We agree on export formats and parameter mapping up front, then test a sample spool to validate nesting and cut lists before full release.