/ Field knowledge · IMC 506.4
Type II exhaust is not a loose arrow.
IMC 506.4: Type II exhaust is not a grease duct — and it is not a loose arrow on the plan. Rigid metallic. Run the 3-10-10-10-30 termination check before the roof plan freezes.
Educational 2024 IMC 506.4 (Daily Code Talk Type II ducts & terminations). Confirm adopted edition. If the appliance produces grease-laden vapors, Type I grease-duct rules apply regardless of the hood label. Do not use flex or nonmetal duct.
- 506.4.1: ducts and plenums must be rigid metallic. Construction, install, bracing, and supports follow Chapter 6. Positive-pressure or moisture-/waste-heat-laden runs must be constructed, joined, and sealed in an approved manner.
- 506.4.2 terminate per the hood manufacturer and:
- Minimum 3 ft from openings into the building.
- Minimum 10 ft from property lines or buildings on the same lot.
- Minimum 10 ft from outside air intake.
- Minimum 10 ft above grade.
- If above roof: minimum 30 in above the roof surface.
- Minimum 30 in from exterior vertical walls.
- Protect against local weather. Do not discharge onto walkways. Meet IBC exterior-wall opening protectives.
Field check from Daily Code Talk: 3 ft openings · 10 ft property/same-lot buildings · 10 ft OA intakes · 10 ft above grade · 30 in above roof and 30 in off walls. If any one is tight, relocate now — not at inspection.
Flex to the Type II outlet
Nonmetal duct and missing sealing on a positive-pressure dishwasher run are the common redlines. Distances belong on the drawing, not only in the spec.
Source: DCT 506.4 · tool: 3-10-10-10-30 screen · hoods: 507.3 · discharge: 501.
What to send
The roof/exterior outlet location and distances to openings, intakes, property line, and grade.
If the Type II outlet is near a door
Send the roof plan. Masterbuild will say whether 506.4 even clears 3-10-10-10-30 — or the outlet has to move.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Confirm the adopted edition. NET cfm and gages below are 2024 IMC model-code education from Daily Code Talk — not a hood selection.