Radon Gas Mitigation

Radon gas in existing homes

What is radon gas?

Radon is a gas formed by the breakdown of uranium, a natural radioactive material found in all soil and rock.  You can't see it, smell it or taste it.  

Radon gas can enter at any opening where the house contacts the ground, such as through cracks and holes in floors and foundations.  When radon gas escapes into the air outside it is not a concern because the air dilutes it. However radon gas can be harmful when it escapes into enclosed spaces such as a house.

Please visit Health Canada for more detailed information.

Radon gas is a serious health issue

Exposure to radon is the second leading cause of lung cancer after smoking and the leading cause of lung cancer for people who have never smoked. The risk depends on the level of radon gas in the home and how long a person is exposed. 

Radon gas testing

Please visit Health Canada for important information on Radon Testing Your HomeQuestions? Please contact Health Canada at 1-833-723-6600.

Most homes will have some radon gas in them.  The only way to know how much gas is in the home is to measure it. Radon levels can vary throughout each day. For accurate results, radon levels should be measured for at least 3 months over the winter season.  No matter where your home is located, the only way to know the radon gas level is to test. Even homes located next to each other can have varying levels of radon.

There are two options for testing a house for radon: 

  1. Purchase a do-it-yourself radon test kit
  2. Hire a certified radon measurement professional to perform the test in your home

Reducing the level of radon in your home

If the radon level is high, homeowners should take action to reduce it. Fix your home if the radon level is higher than the Canadian Guideline of 200 Becquerels per metre cubed (Bq/m3). Radon levels in most homes can be reduced by approximately 80% for about the same cost as other common home repairs such as replacing the air conditioner or furnace.

A building permit is not required to undertake radon mitigation in existing buildings where the work involved is non-structural, does not affect HVAC or plumbing systems or fire protection and the mitigation work does not interfere or pose a threat to the health and safety of the occupants.

New home construction - requirements for radon gas mitigation

Construction of a new house, semi-detached house, townhouse, or residential addition will require radon gas mitigation measures in compliance with the Ontario Building Code. Part 9 of the Ontario Building Code contains prescriptive compliance methods for soil gas mitigation.

The building permit applicant must provide a completed Radon Mitigation Form with the building permit application.

The builder is required to implement one of the following three radon gas mitigation methods:

Option 1:  Soil Gas Barrier System

  • 6 mil polyethylene under concrete floor
  • 6 mil polyethylene between concrete floor and separate floor over the slab
  • Perimeter of concrete slab and all penetrations through the slab shall be sealed

Option 2:  Subfloor Depressurization, (Full installation)

  • Minimum 100mm (4”) pipe installed at or near center of floor area
  • Increase amount of granular under the floor at pipe inlet location
  • Pipe extended to exterior of the building
  • System must include an in-line fan

Option 3:  Subfloor Depressurization, (Rough-in only)

  • Minimum 100mm (4”) pipe installed at or near center of floor area
  • Increase amount of granular under the floor at pipe inlet location
  • Pipe to extend above floor with removable seal pipe must be clearly labelled for removal of soil gas
  • NOTE:  When Subfloor Depressurization is roughed-in only, testing for Radon is mandatory once the home is occupied.  Testing must occur over the winter months for a period of not less than 91 days. The test results must be submitted to the City of Niagara Falls – Building Services. If the test results exceed Ministry tolerances a full depressurization system must be installed. 

New Home Warranty - Radon Gas

New homes in Ontario come with a new home warranty that is provided by the builder and backed by Tarion. The warranty covers radon gas levels exceeding 200 Bq/m³ in new homes for seven years from the date of occupancy.

Sources of Information