/ Field knowledge · IMC 507.1.6
CFM will not fix a hood that is too short.
Most hood failures are geometry failures. If the hood is too short, too high, or too far back, it will never capture consistently — no matter how much cubic feet per minute (cfm) you throw at it. IMC 507.1.6 applies to both Type I and Type II. Canopy: inside lower edge at least 6 in beyond the cooking surface on all open sides; front lower lip no more than 4 ft above the cooking surface. Noncanopy: no more than 3 ft above, set back no more than 1 ft.
Educational 2024 International Mechanical Code (IMC) 507.1.6 from Daily Code Talk. Confirm the adopted edition. Distinct from NET cfm (507.2.10) and 507.2 construction. This is not a hood selection. Flush exception: the hood can be flush at the appliance edge where that side is closed off by a noncombustible wall or panel.
- Canopy (Type I and II): 6 in minimum overhang on all open sides. Lip height: 4 ft maximum above the cooking surface.
- Noncanopy: 3 ft maximum above the cooking surface. Setback: hood edge no more than 1 ft from the edge of the cooking surface.
- Dimension it on plan and section. Missing section views are the leading cause of overhang comments — overhang and hanging height can only be verified in section.
- Size the hood to the appliance footprint first, then calculate exhaust from the sized hood. Exhaust rate and overhang are related but separate. A hood sized to cfm instead of the lineup is the usual miss; moving it at inspection is structural, exhaust, and makeup-air rework.
On the set: hood tag with a capture-geometry line — canopy 6 in min overhang + 4 ft-0 in max lip, or noncanopy 3 ft-0 in max height + 1 ft-0 in max setback. Show wall/panel closures where using the flush exception.
Canopy drawn tight to the fryer with no 6 in overhang
Or a noncanopy hung at 4 ft. Smoke rollout, odor complaints, failed capture tests. Cfm will not fix it.
Source: Daily Code Talk — IMC 507.1.6 · tool: Overhang screen · Type I: 507.2 · filters: 507.2.8.
What to send
Kitchen plan and a section (or elevation) through the hood, the appliance lineup, and whether the hood is canopy or noncanopy.
If the hood is drawn tight to the equipment
Send the plan and a section. Masterbuild will say whether 507.1.6 still has a 6 in overhang miss — or a lip still over 4 ft.
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. 6 in overhang, 4 ft canopy lip, 3 ft / 1 ft noncanopy, and the flush-to-wall exception are 2024 IMC 507.1.6 education from Daily Code Talk — not a hood design. This page is not legal advice.