Code Applied by the app hvac.duct.grease-duct
Grease duct metal and its weight
A commercial kitchen hood's exhaust duct is welded carbon steel of at least 16 gauge or stainless of at least 18 gauge, never the galvanized gauge schedule, so the Duct tool prices a grease run at that fixed gauge and its own sheet weight.
| When | The app uses |
|---|---|
| carbon steel (black steel), minimum gauge | 16 ga |
| stainless steel, minimum gauge | 18 ga |
| 16 gauge carbon steel sheet | 2.5 lb/ft² |
| 18 gauge stainless sheet | 2 lb/ft² |
| cleanout spacing on horizontal duct, at most | 12 ft |
- Source
- IMC · 506.3.1.1 Grease duct materials (NFPA 96 7.5.1 says the same) · read the public text
- Editions checked
- 2021
- Used by
- Duct Schedule
- Amendments
No state or local amendment to this rule is on file. Not on file means the model code as written — check your jurisdiction.
A model code the authority having jurisdiction adopts.
A grease duct is a chimney for a fire. The code fixes its metal: carbon steel not less than 0.055 in (16 gauge) or stainless not less than 0.044 in (18 gauge), joints continuously welded liquid-tight, cleanouts at changes of direction, and no damper of any kind inside it. The SMACNA gauge schedule the Duct tool carries is for galvanized supply, return and general exhaust at low pressure; it would call an 18 in round at 1 in w.g. 24 gauge and weigh it at about half what the welded duct weighs.
What the app does with it
A duct run has a material: galvanized by default, or welded black steel or welded stainless from the Duct dialog or the run's right-click menu. A grease run tallies on its own row of the Duct Schedule at the fixed gauge above and the sheet weight above, with its fittings priced the same way, and the per-size gauge override never touches it.
The schedule's Grease duct block then prices what is not sheet metal by the pound, on its own lines outside the bid weight: cleanouts by the piece, one at each change of direction (each elbow on a grease run) and one per 12 ft of horizontal run (NFPA 96 7.4), and the listed wrap by the square foot of duct surface, straight duct only, since fittings are wrapped by the piece. The welding labor stays with your pricing.
Cited by section, not reprinted: the code text belongs to its publisher. Company practice is not a rule here — it lives with your pricing.