/ Field knowledge · IMC 804.3.5
Height above this roof is not the whole check.
Rooftop coordination fails when the vent is reviewed only as a height. Mechanical-draft vertical termination is spatial: horizontal separation and vertical relationship to walkways, intakes, roof structures, openings, and the listed cap. A dimension visible only in plan rarely proves the height relationship that actually governs the conflict.
Educational 2024 International Mechanical Code (IMC) 804.3.5 from Daily Code Talk. Confirm the adopted edition, listing, manufacturer instructions, and actual roof geometry. Distinct from horizontal power-exhauster termination (804.3.3–804.3.4) and Type L / listed-vent heights (802.5–802.6). This page does not reprint 804.3.5 dimensions — verify them in the adopted text. This is not a termination layout. Packet: 804.3.5 PDF · ES.
- Daily Code Talk identifies vertical-termination controls for adjacent walkways, forced-air inlets in the stated horizontal review range, roof structures, doors/windows/gravity air inlets, vent caps, and separation from roof structure.
- A vent can clear a roof surface and still be too close to a higher roof, parapet, penthouse, outdoor-air intake, opening, or pedestrian route.
- Run two checks together: in plan, horizontal separation to intakes, openings, equipment, and roof structures; in section/elevation, relative height, roof relationships, listed cap, discharge path, and walkways.
On the set: roof plan and a roof-section callout wherever the termination is near a change in roof elevation or a parapet. Identify the vent cap and listing/manufacturer basis. Reconcile wind or enclosure conditions that need qualified design review. Do not leave the termination to field judgment.
Height above this roof, ignoring the next roof
Missed conflicts drive recirculation, draft problems, corrosion/staining, water entry, carbon monoxide, rework, and failed inspection. The permit set should show enough geometry that the AHJ, contractor, and commissioning team reach the same conclusion without redesigning the termination in the field.
Source: Daily Code Talk — IMC 804.3.5 · horizontal: 804.3.3–804.3.4 · 802 heights: 802.5–802.6 · 801.14: inlet side.
What to send
Roof plan and a section or photo showing nearby parapets, higher roofs, intakes, and the proposed termination. Draft type (mechanical vs gravity).
If the power vent terminates at the roof
Send the roof plan and the section. MasterBuild will say which adjacent roof or intake still has no dimension — before the curb is set.
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. 804.3.5 dimensions are not reprinted here — verify the adopted text, listing, and manufacturer instructions. This page is 2024 IMC education from Daily Code Talk, not a termination design or legal advice.