/ Field knowledge · IMC 511
If it is unlabeled, it will get capped.
IMC 511: a subslab soil exhaust system pulls soil gases from under the slab and discharges them above the roof so they do not build up under or inside the building. If it is labeled like a plumbing vent, it gets capped on the next remodel.
Educational 2024 IMC 511. Confirm adopted edition. This is not a radon design or a soil-gas survey.
- Materials: UL 181 listed Class 0 air-duct material, or IPC-approved sanitary DWV/vent materials (cast iron, galvanized steel, copper Type DWV or heavier, or plastic piping).
- Do not trap the duct. Minimum slope 1/8 in per 12 in (1%) so it drains.
- Terminate through the roof: at least 6 in above the roof and at least 10 ft from operable openings or outdoor-air intakes. Dimension it on the roof plan — do not just note it.
- Permanently label the duct at each floor level.
Added after the slab
If the project is in a high-radon area, design a passive riser with a future-fan provision before the slab. After pour, routing options collapse.
Source: DCT 511 · discharge: 501.3.
What to send
Whether this is new slab or existing, roof plan with nearby intakes/windows, and any radon or vapor-intrusion report.
If the riser looks like a plumbing vent
Send the roof plan and whether the slab is already poured. MasterBuild will say whether 511 clearances even work — or the termination is in the OA intake.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
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