/ Field knowledge · IMC 603.18
Air devices are not finish items.
The duct can be sized and installed correctly and the system still fails review at the air outlet. Registers, grilles, and diffusers are not finish items. They have to be installed per the manufacturer, adjustable for balancing with access to that adjustment, and kept out of wet-room floors the International Building Code (IBC) requires to be smooth, hard, and nonabsorbent. Dwelling units are the exception.
Educational 2024 International Mechanical Code (IMC) 603.18–603.18.2 from Daily Code Talk. Confirm the adopted edition. Distinct from air balancing (608) and flexible ducts (603.6). This is not a device schedule.
- 603.18: install per the manufacturer. Supply-air adjustment in the branch duct or at each individual register, grille, or diffuser. Any balancing device used for that adjustment must have access.
- 603.18.1: floor registers must resist a 200-pound concentrated load on a 2-inch-diameter disc without structural failure.
- 603.18.2: prohibited in the floor, or the upward extension of the floor, within toilet and bathing rooms that must have those IBC wet-room surfaces. Exception: dwelling units.
On the set: how each supply device will be balanced, balancing-damper or adjustment access, floor-register load basis, and wet-room floor coordination on the architectural sheets. Comments show up late because air devices get treated as finish.
A floor grille in a public restroom
Or a supply with no accessible balancing means. The permit comment arrives after finishes are bought. Show the adjustment and the wet-room restriction before the interior elevations lock.
Source: Daily Code Talk — IMC 603.18 · tool: Outlet screen · balancing: 608 · dispersion: 603.17.
What to send
The air-device layout (especially restrooms), whether each supply has an accessible balancing means, and whether any floor registers are in public wet rooms.
If a floor grille is drawn in a public restroom
Send the layout. Masterbuild will say whether 603.18.2 still has a wet-room floor miss — or 603.18 still has no accessible balancing means.
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. The 200-pound floor-register load and the wet-room floor prohibition are 2024 IMC 603.18 education from Daily Code Talk — not a device specification. This page is not legal advice.