What Is Included in a Radon Mitigation Design Package for Large Buildings

A radon mitigation design package for a large building contains four things: scaled drawings of the sub-slab collection system and vent stack routing, written specifications for the soil gas barrier and every sealed penetration, provisions for fan conversion and post-construction testing, and the code references plus a certified radon professional's review that let a plans examiner and a lender approve it. It is a design deliverable that travels with your permit set. It is not an installation bid, and for any building other than a one- or two-family dwelling it is drawn to ANSI/AARST CC-1000-2018, the consensus standard for soil gas control systems in new construction of buildings intended for human occupancy.

This page walks through each part of the package, what a reviewer checks it against, and how the contents shift when the building is already standing.

The drawing set is the core of the package and the part your contractor actually builds from. For a large building it covers the entire foundation footprint, not a single representative bay. A complete set shows:

• A sub-slab collection layout: the gas-permeable layer beneath the slab, each suction point location, and the spacing logic that ties them together across every slab-on-grade and below-grade area. Large footprints usually need multiple suction points because one point cannot depressurize soil under an entire wing.
• A soil gas barrier plan: where the membrane runs, how it laps, and how it stays continuous across footings, grade beams, elevator pits, and construction joints.
• Vent stack routing: the path from each suction point up through conditioned space to a discharge above the roofline, located clear of operable windows and outdoor air intakes.
• Riser diagrams and sections at the details that fail most often, such as pipe penetrations, sumps, and slab edges.

Reviewers read these sheets the way they read a plumbing riser: line by line against the standard. A package that shows the layout in plan, section, and detail gets through review faster than one that leaves the examiner to infer how the barrier crosses a grade beam.

The written specifications back the drawings with the material and performance requirements the standard sets. Expect the package to specify:

• The gas-permeable layer material and depth, typically clean coarse aggregate, and the vent matting alternative where aggregate depth is not available.
• The membrane product class, thickness, lap widths, and the sealant used at every penetration and joint, so the barrier is airtight as installed rather than airtight on paper.
• Vent stack pipe material, diameter, and labeling, sized so the system can move the design airflow when it runs passively on stack effect alone.
• Active-conversion provisions: the fan location on each stack, an electrical rough-in beside it, and a system monitor, so a passive system can be converted with a field change instead of a redesign.
• Post-construction testing requirements, because the design's job is to hold indoor radon below the EPA action level of 4 pCi/L, and the only way to confirm that is to test occupied levels after the building is closed in.

That last item matters commercially as well as technically. If testing shows the passive system is not pulling enough, the conversion provisions already in the package turn the fix into installing a fan, not cutting a finished slab.

The third part of the package is what makes it approvable rather than merely buildable. The EPA recognizes the ANSI/AARST consensus standards as the radon standards of practice, and plan reviewers, HUD environmental staff, and lenders key their checklists to those documents. The package therefore carries:

• Explicit references to the governing standard on the sheets themselves, so the examiner can map each detail to the requirement it satisfies.
• A review by a certified radon professional, the credential the compliance chain expects to see attached to the design.
• Inspection provisions for the construction stage. The 2023 revision cycle moved construction-stage verification from optional to required, which means the package has to state what gets inspected before, during, and after the pour.

A design that skips this layer often costs more than it saves. When a lender's environmental reviewer finds radon addressed by a note that says “contractor to provide radon system per code,” the response is a request for a real design, and the schedule absorbs the delay.

Which standard the package answers to depends on whether the building exists yet. CC-1000-2018 applies to new construction of buildings intended for human occupancy other than one- and two-family dwellings, which puts apartment buildings, condominiums, schools, offices, and mixed-use projects in scope. The design goes into the permit set and the system is built into the slab from day one, which is the cheapest point in the building's life to install it.

For a building that is already standing, the package is drawn instead to SGM-MFLB-2023, the soil gas mitigation standard for existing multifamily, school, commercial, and mixed-use buildings. The contents shift with it: a diagnostic phase replaces the assumption of a clean aggregate layer, suction points are located from pressure-field measurements rather than a blank plan, and routing has to thread existing chases and roof penetrations. The deliverable is still the same idea, a stamped document set a mitigation contractor prices and installs from, but the engineering starts from measurements instead of drawings. If your project is an existing building, the CC-1000 reference page explains where the new-construction standard stops and the existing-building standard takes over.

The package is derived from your building, so the starting point is your architectural set. A vector PDF exported from CAD or Revit is enough: the foundation geometry drives the collection layout, the stacking plans drive the vent routing, and the occupancy type sets the standard the sheets reference. From there the workflow lays out suction points, details the barrier, sizes and routes the stacks, writes the specifications, and puts the result in front of a certified radon professional for review.

If you are scoping a multifamily project specifically, the multifamily building-type page covers how unit stacking affects the design. Pricing is flat by building type and published on the pricing page, so the number is known before any work starts. When you are ready, request a quote with your plan set and you get back a fixed price and a delivery date for a permit-ready, standard-referenced design package.