Radon action guide for municipalities: Building codes, bylaws and provisions

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Building codes

Varying building code provisions across Canada

There are radon provisions in the (model) National Building Code (with the radon provisions last updated in 2010). Many provinces have incorporated some radon provisions in their code.

To unpack the variety of codes in Canada it may be useful to analyze different radon reduction strategies, ranging from the most rudimentary to the most effective.

Soil gas barriers

This involves placing a membrane between the slab and the ground below. Soil gas barriers are not considered an effective stand-alone radon reduction strategy.

Radon rough-in with stub

This involves the sealing of radon (and other soil gas) entry points, granular material below the slab, and a radon rough-in ‘stub’. This is a short vent pipe which rises from the floor and is capped. This was added to Canada’s National Building Code in 2010 and has been adopted into several provincial and territorial building codes. There is a significant risk that high radon environments remain untested and unmitigated. Current best practices require more complete systems.

Passive sub-slab depressurization

This involves a pipe installed through the foundation that runs upwards through the inside of the building and vents to the outside at the roofline. British Columbia’s building code started with the rough-in stub (following the National Building Code). A study found the radon rough-in stub was generally insufficient. This led to changes to the BC Code to require an outside venting pipe. While often effective at reducing radon, these systems cannot be relied on to reduce high radon concentrations to below the guideline level. Homes with these systems should still have the radon level tested.

Learn more about:

Active sub-slab depressurization

This involves adding a fan to passive sub-slab depressurization systems to further increase the reduction of radon. Québec’s Construction Code now requires:

Table 1: Building codes in Canada and radon system requirements
Building code If limited area of application Soil gas barrier Radon rough-in with stub Passive sub-slab depressurization

National Building Code of Canada, 2015



Explained here


Provinces and territories that follow the National Building Code: Saskatchewan, Manitoba, New Brunswick, Nova Scotia, Newfoundland and Labrador, Northwest Territories, Yukon, Nunavut. PEI in major municipalities.



Explained here


British Columbia Building Code, 2018

Select municipalities predominantly east of Coast Mountains, see Table C-4

Locations in British Columbia Requiring Radon Rough-Ins



s. 9.13.4

National Building Code – 2019 Alberta Edition



Explained here, to be augmented with testing and other design as per and “good engineering practice’


Ontario Building Code, 2017 in Conjunction with Supplementary Standard SB-9, providing three options

Areas of Ontario with known radon problem

s. and Supplementary Standard SB-9, explained here(with voluntary radon gas testing)

Supplementary Standard SB-9, explained here 4(b) and Supplementary Standard SB-9, explained here

Quebec Construction Code


Quebec Construction Code A- (prior to Sept 2020)

Quebec Construction Code, (as of September 2020)

Quebec Construction Code, (as of September 2020), if test results show need

Current best practices in mitigation are outlined in the Canadian General Standard Board’s 2019 “Radon control options for new construction in low-rise residential buildings” and should be referenced in building codes. The standard provides detailed technical prescriptions for radon mitigation strategies.

There are significant benefits to targeting radon prone areas and requiring new homes to have operational systems (at least a passive sub-slab system), ensuring that homes are built with less radon in them and reducing the incidence of radon-induced lung cancer in higher risk regions.

If building codes continue to require forms of ‘rough-ins’ that are incomplete, provinces and territories should consider requiring clear labelling on these systems stating that they are incomplete, and that further radon testing is required by homeowners once they occupy the home. Provinces and territories can consider requiring builders to leave radon test kits and informational guides with new homeowners and requiring occupants of new homes to test for radon.

Learn more about:

Radon in municipal building codes

In some provinces (Quebec, Newfoundland and Prince Edward Island), there are possibilities for municipalities to put more stringent requirements in place that go beyond provincial building code requirements.

Some municipalities independently enact codes that meet the National Building Code (including for radon).

Municipalities that have implemented their own radon standards include:

In Ontario, the radon provisions only apply in “known radon areas”. The following municipalities have taken steps to implement the Building Code provisions and provide explicit direction to builders:

In British Columbia, the BC Building Code, 2018 lists specific municipalities where radon mitigation systems are needed (at Division B Appendix C Table C-4. Locations in British Columbia Requiring Radon Rough-Ins). Municipal governments can take steps to be added to this list if they have evidence of elevated radon in their area.

Building Code Enforcement

Municipal building inspectors are encouraged to make use of Canadian- National Radon Proficiency Program (C-NRPP) Training for Building Professionals: Controlling Radon in New Canadian Homes (CRNCH): CNRPP-EL-9.

Hamilton, Ontario’s radon inspection process can serve as an important example. The web page clearly indicates builders’ and owners’ responsibilities. For new construction and/or additions, the property owner or builder is required to arrange for inspections relating to:

As well, depending on the radon gas mitigation option chosen by the builder, it is the property owner’s responsibility to conduct radon gas testing (following specified procedures) and submit the results to the City. Where mandatory radon gas testing results come back above 200 Bq/m³, the property owner is to install an active subsoil depressurization system and ensure any resultant decrease in soil temperature will not adversely affect the foundation using documentation provided by a qualified person.

Standards of maintenance bylaws

Housing and maintenance standards

Many provinces have specific wording in municipal law allowing local governments to make standards of maintenance bylaws. For examples see:

In some cases, there is a process for approval of standards of maintenance bylaws:

Provinces also at times provide specific language directing municipalities to receive complaints, make investigations and issue orders against landlords.

Municipalities are encouraged to have standard of maintenance bylaws that protect renters indoor air quality, including from radon. Radon specific provisions can specify that:

Enforcement of bylaws

Municipalities should take steps to enforce standards of maintenance bylaws.

An example of an enforcement bylaw is the City of Waterloo’s Rental Licensing Bylaw 2011-047. This has a number of provisions that could be used to enforce standards of maintenance:

Iowa City, Iowa has instituted Radon Testing Requirements for rental properties. This plans for a 2-year inspection cycle whereby all single family detached and duplex units that become rentals will need to be tested and come into compliance with the regulation.

Radon requirements in public spaces

Radon provisions for clean air and health bylaws

Municipalities can regulate radon in indoor spaces, including for businesses, recreation centres and other areas accessible to the general public. Similar to smoking regulations, these can be made a part of general health or clean air bylaws. Details can include:

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