Radon-control design for multifamily buildings
New multifamily buildings carry the same soil-gas risk as single-family homes, but at a scale where a generic prescriptive detail no longer fits. Garden apartments, podium construction, and mid-rise residential all sit on slabs or below-grade levels that contact soil, and radon entry routes multiply with every shared corridor, elevator pit, and utility chase.
ANSI/AARST CC-1000-2018 is the consensus standard for radon-resistant design in new construction of multifamily and other large buildings. It calls for an engineered approach: gas-permeable material below the slab, a continuous soil-gas-retarder membrane, sealed penetrations, and a vent pipe network sized for the building rather than a single dwelling.
We read your architectural set, lay out the sub-slab collection and vent routing, size the riser network, and produce a code-referenced design package. A certified radon professional reviews and signs off on every package before it ships, so the credential that the compliance chain expects is already in place.
What the design package covers
- Sub-slab gas-permeable layer and soil-gas-retarder membrane specification
- Vent pipe routing and riser network sized for the building footprint
- Sealing details for slab penetrations, expansion joints, and below-grade walls
- Provisions for future active fan installation if post-occupancy testing warrants it
- Code-reference summary keyed to ANSI/AARST CC-1000-2018
Governing standard
Further reading
HUD Radon Requirements for Multifamily: Testing & Mitigation
What HUD multifamily financing expects for radon, and where engineered design built to the AARST standards fits.
How to Design Radon Mitigation for Multifamily Buildings
Designing radon mitigation for a multifamily building to ANSI/AARST CC-1000-2018: package scope, passive vs. active systems, and HUD requirements.
Radon Vent Stack Sizing for Multifamily Buildings
How radon vent stack sizing works for multifamily buildings: the 2-inch, 3-inch, and 4-inch airflow bands, and what pressure field extension decides.
Passive vs. Active Radon Control in New Construction
Passive radon control vents soil gas on stack effect; active adds a fan. New construction starts passive, converting only if a test exceeds the limit.
Radon Mitigation Design Package Contents for Large Buildings
What a large-building radon mitigation design set contains: collection layout drawings, barrier and sealing specifications, vent routing, and fan provisions.