What To Know About Radon Mitigation for Multi-Unit Buildings

Managing a property with multiple residences means accounting for shared structures, occupied spaces, and systems that may serve more than one area. When elevated radon levels need to be reduced, building characteristics can shape how the work is planned and installed. Radon mitigation for multi-unit buildings requires a system that fits the property’s foundation, layout, and available routing options.

How Multi-Unit Mitigation Works

A radon mitigation system creates negative pressure beneath the building to draw soil gas away from occupied areas. Depending on the foundation, suction may be created beneath a concrete slab, through a sump pit or drain tile, or below a sealed vapor mat. Larger or more complex properties may require multiple suction points to effectively reach different foundation areas.

Once the soil gas enters the system, a fan moves it through connected piping to an exterior exhaust point. The piping may be routed through an attic or along a side or rear wall, depending on the property and applicable requirements. From there, the system releases the gas outdoors, up and away from the building.

What Makes Multi-Unit Properties Different?

Radon mitigation for multi-unit buildings often requires planning around several connected spaces. A multi-unit property may need a system that accounts for how air and soil gases move across a larger footprint than in a single-family home.

Here are features of multi-unit properties and how they can shape the mitigation system or plan:

• Shared foundations can require the system to account for several units at once.
• Separate or connected slab sections can affect suction point placement.
• May require vapor mat and sealed vapor barriers and a different suction method than slab areas.
• Common hallways and utility areas can influence where piping and equipment can be routed.
• Limited piping locations can restrict where system components can be installed.
• Available electrical access can affect where fans and related equipment are placed.
• Suitable exterior exhaust locations can determine how piping is routed out of the property.

Designing the Mitigation System

No two multi-unit properties are built exactly the same, so the mitigation system has to be planned around the structure itself. Professional commercial radon mitigation services can identify the best locations for suction points and equipment so the system can serve the areas that need it.

Suction Point Locations

A suction point is an opening or connection that allows the mitigation system to draw soil gas from beneath the structure. Placement depends on how effectively each location can create the necessary pressure beneath the building.

Pipe and Fan Placement

Piping carries soil gas from the suction area to an exterior exhaust location. The route may pass through an attic or run along a side or rear exterior wall, depending on the building and applicable requirements. The fan also needs a suitable location that allows it to maintain airflow through the system while remaining accessible for service.

New Multi-Unit Construction

Phase One Vapor Mat

The VAPORMAT™ System is enveloped in a filter fabric and is comprised of 95% air space, allowing the radon and other soil gases and vapors to be channeled to the riser pipe connection. The Vapor Matt is installed around the perimeter of the property for maximum effectiveness.

Phase One Stub Ups

Once the foundation walls are in place for the building. A radon mitigation system stub-up will need to be put into place. Depending on the specs of the building, the required type and required number of stub(s) will be installed. Prior to starting the installation, the placement of the stub(s) will need to be approved by the G.C. or the engineer.

Phase 2 Full Passive Radon Mitigation System Installations

There will be a full passive soil depressurization system using white 3”, or 4” PVC pipe installed. The system will start at the stub. The pipe will be routed vertically through the structure of the building. Then the piping will be vented through the roof. In the attic space 110 volt power will need to be supplied by others. This is for the activation of the system by installing a Radon Fan.

Phase 3 Charcoal Radon Testing

An activated charcoal test kit provided by a third-party company will be delivered, set up, taken down, and mailed in by our technician. The testing confirms if the passive system alone is going to mitigate the building.

Phase 4 Full Active System

A fan is installed to convert the passive system to an active system to further reduce radon levels if needed.

Choosing a Mitigation Method

The method used to create suction depends largely on the foundation and the features already present beneath the property. Some buildings may use a single method throughout, while others may require a combination to address different foundation conditions. New construction foundations utilize a vapor mat and vapor barrier as part of the method.

Common mitigation methods include:

• Sub-slab depressurization: Creates suction beneath a concrete floor through an opening in the slab.
• Sump-pit depressurization: Connects mitigation piping to an existing sump area when the property configuration allows it.
• Drain-tile depressurization: Uses existing drain tile as part of the suction network beneath the structure.
• Submembrane depressurization: Draws air from beneath a well-sealed vapor barrier installed over exposed crawl space soil.

Installing Around Occupied Spaces

Unlike an empty construction site, a multi-unit property may remain active while work is underway. That can require coordination around residents, common areas, building operations, and spaces with limited access.

Coordinating Unit Access

Some parts of the installation may require access to individual units, shared rooms, basements, crawl spaces, or utility areas. Property managers may need to coordinate entry so that technicians can access the necessary areas. Identifying those access needs before installation begins can make scheduling easier when several residents or property contacts are involved.

Minimizing Installation Disruption

The system layout can account for how residents use the property day-to-day. When the building configuration and code requirements allow it, piping and other visible components can be routed through practical locations that avoid unnecessary interference. Installation steps can also be organized to reduce repeated access to the same areas.

Meeting Building Requirements

A mitigation system must fit the property physically while also complying with state and local building codes and applicable radon standards. Electrical wiring, conduit, piping, roof penetrations, and exhaust placement may all affect the final installation. In some cases, those requirements can change where components can be located.

The building itself can introduce additional constraints. A preferred pipe route or fan location may not be feasible if it conflicts with structural features or code requirements, so an alternative path may be needed. Properties with specialized construction, such as post-tension slabs, may require additional steps before openings are cut in concrete.

Maintaining the Mitigation System

Once installed, the system should remain accessible for future maintenance and service. Several components work together to keep air moving in the right direction.

Here are the key parts of the mitigation system and what they do:

• The manometer shows the pressure inside the mitigation piping and can indicate when airflow changes.
• The fan keeps air moving through the system so soil gas continues to be drawn away from occupied areas.
• The piping carries soil gas from the suction point to the exterior exhaust location.
• The suction point connects the system to the area beneath the slab, sump pit, drain tile, or crawl space membrane.
• The exhaust point releases the collected soil gas outdoors and away from occupied spaces.

If you notice a change in the manometer reading, unusual fan noise, damaged piping, or any other visible issue, contact our specialists at Affordable Radon Southwestto inspect the system. Follow-up radon measurements can also show how indoor radon levels are responding after mitigation. Keep records of repairs, system changes, and post-mitigation results, so you have a clear history of the system over time.

Multi-unit properties may require careful coordination because foundations, occupied areas, and system components can be interconnected. Effective mitigation starts with understanding those conditions and designing the system around the property. Proper installation and ongoing system care can keep the equipment functioning correctly. With a clearer picture of how the process works, property owners and managers can better understand what to expect from multi-unit radon mitigation.

Affordable Radon Southwest has the expertise to mitigation existing and new construction multi-units. Contact one of our specialists for all your radon mitigation needs.