Radon System Design for New Apartment Buildings

A radon system design for a new apartment building is a plan-specific engineering package that shows how soil gas is collected under the slab and vented above the roof, drawn to ANSI/AARST CC-1000-2018 so your plan reviewer and your lender can approve it. It is a design deliverable for your permit set, not an installation bid. New apartment buildings are explicitly in scope for that standard, so the system has to be designed for the building from the first foundation sheet, not added after the slab is poured.

An apartment building is not a scaled-up house. It has a large slab footprint, stacked occupancies over shared soil, and vertical chases that vent stacks have to follow from the ground to the roof. The radon design accounts for all of that on the same sheets your architect and structural engineer are already working from.

CC-1000-2018 is the consensus standard for soil gas control in new construction of large buildings. It applies to any building intended for human occupancy other than one- and two-family dwellings, which places new apartment buildings squarely in scope. The prescriptive residential radon provisions that cover single-family homes do not carry over, so an apartment project needs a design keyed to the large-building standard from the start.

The reason is practical. A plans examiner checks the radon package against CC-1000-2018 line by line, and the EPA recognizes the ANSI/AARST consensus standards as the radon standards of practice. A design that only gestures at radon, or that leaves it to whoever installs the system, gives the reviewer nothing to approve and slows the permit.

The design is the document set a contractor builds from and a plans examiner stamps. For an apartment building it covers the full footprint and every stacked level above it, not a single foundation. A complete package includes:

• A sub-slab collection layout: the gas-permeable layer, suction point locations, and the spacing that ties them together under each slab-on-grade and below-grade area.
• A continuous soil gas barrier specification: the membrane, the laps, and how it is sealed at every penetration, footing, and construction joint across the footprint.
• Vent stack routing and sizing from each suction point up through the building to a discharge above the roofline, clear of operable windows and air intakes.
• Passive and active provisions: where the system runs passive, where it is built to convert to active, and the electrical rough-in for any fan.
• Code references and a certified radon professional's review, so the credential the compliance chain expects is built into the deliverable.

Because the package travels with your permit set as a standalone document, your contractor installs from it and your examiner checks it without design being bundled into a single installation bid.

Every CC-1000 design starts passive and is engineered so it can go active without rework. The two modes differ in how the soil under the building is depressurized:

• A passive system relies on the stack effect. Warm air rising in the vent stacks creates enough draw to pull soil gas up and out with no fan. It runs silently, uses no power, and on many sites holds indoor radon below the action level on its own.
• An active system adds an inline fan to each stack. It is specified when the footprint is large, the soil is tight, or post-construction testing shows the passive draw is short. Because the design already fixes the fan position, the wiring, and the labeling, conversion is a field change rather than a redesign.

For an apartment building, designing for both from the outset matters more than it does for a house, because the finished stacks run through occupied units. Locating the active provisions on the passive sheets is the difference between a one-line field upgrade and opening a chase behind tenants.

The routing question is what makes apartments different. Each suction point needs a path to the roof, and in a stacked building that path runs vertically through the same chases that carry plumbing and mechanical risers. The design coordinates stack locations with those chases early, sizes each stack for the collection area it serves, and terminates every discharge above the roofline and away from operable windows, balconies, and air intakes on the units below.

Getting the routing on paper before the structure is framed avoids the two expensive failures: a stack that has nowhere to go once the shafts are laid out, and a discharge that re-enters the building through a window or intake it was meant to clear. Both are cheap to solve on a drawing and costly to solve in a finished building.

If the apartment project is HUD-financed, radon control stops being optional. HUD recognizes ANSI/AARST CC-1000-2018, “Soil Gas Control Systems in New Construction of Buildings,” as the applicable standard for new-construction radon control. In practice the lender and the plan reviewer both expect a design keyed to CC-1000-2018 and signed by a certified radon professional in the package they approve. A design bundled into an installer's scope without its own stamped sheets slows the financing down.

The same logic applies to any apartment building inside the standard's scope, financed or not. A design built to the governing standard, carrying the credential the reviewer looks for, answers the radon question before it is asked.

The design is drawn from your building, so it starts with your plans. Send a vector PDF architectural set exported from CAD or Revit. The workflow reads the foundation geometry, lays out the collection and vent system across the footprint, specifies the barrier and sealing details, routes the stacks through the building, and references the governing standard. A certified radon professional reviews and signs the result. You receive a code-referenced package ready to drop into your permit set, quoted up front with no retainer and no bundled installation contract.

If you are scoping a new apartment, condominium, or mixed-use building, start with the multifamily building-type page for what the package covers, then request a quote with your plans and we return a fixed price before any work begins.