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Whether you own a new home or condo, are considering buying one, or just love to dream about it, the Open Door blog is here to share stories that can help you protect what is likely the biggest investment of your life.

The Open Door blog is published by Tarion, a non-profit corporation that administers Ontario’s New Home Warranty Plan and registers all new home builders in Ontario. Click here to learn more about us.


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Is your home radon safe?
November 14, 2017
Open Window

What you need to know about radon

If you have water leaking into your basement, eventually you’re going see the signs – dampness, mould or even floor or ceiling damage. When it comes to radon, however, this invisible gas can build up in enclosed areas of your home and you won’t be able to tell. Radon can be found virtually everywhere and that means that almost every house in Canada will have some radon. Concentration levels can vary widely from area to area and even among different homes in the same neighbourhood. With proper ventilation, radon will dissipate causing no problems at all. Unfortunately, enclosed spaces without good airflow can develop dangerously high radon levels. Long-term exposure to excessive radon can increase the risk of lung cancer. November is Radon Action Month so it’s the perfect time to learn the top five facts about radon.

  1. It’s a naturally occurring gas. Radon is created by the breakdown of uranium found in rock and soil. When it escapes from the ground and mixes with the air, it is diluted to very low levels. The problem with radon arises when it seeps into a home, often through cracks in basement floors or foundations, and gets trapped in enclosed spaces like basements and crawlspaces.
  2. You can’t see it, smell it or taste it. You can see mould and you can smell natural gas, but your senses can’t detect radon. There’s no way to determine if radon is going to be a problem before a home is built and most homes are not tested after they’re built.
  3. It can be detected. Radon is measured in units called ‘becquerels per cubic metre’ and Health Canada has set 200 becquerels per cubic metre as the safe limit for radon in a home. Levels of radon in a home can be detected using either a do-it-yourself radon test kit or by hiring a radon measurement or mitigation professional.
  4. It can be an issue in both homes and condominium buildings. You might think that only homes with basements and crawlspaces have to be concerned about radon. But enclosed areas in condominiums can also be affected. For example, radon can build up in the basement of a condominium townhouse or can seep through cracks in the foundation of a parking garage of a high-rise.
  5. Excessive levels of radon are not a “defect”. Radon in a home is not caused by a builder defect. It can’t be detected prior to home construction and a high radon level does not mean that your builder made an error or omission during construction.


The warranty requires that a home be safe and fit for habitation, which is why excessive radon levels are covered.

If you’re a new owner and you’re concerned about radon, the good news is that your statutory warranty includes coverage for high radon levels that lasts for the full seven years of your warranty. The warranty requires that a home be safe and fit for habitation, which is why excessive radon levels are covered. Ontario is one of only two Canadian jurisdictions that cover radon remediation in the statutory new home warranty. But whose responsibility is it to test for radon? That depends. If you’re an owner of a newly built home, you are responsible for radon testing. If you’re a condominium unit owner, you are responsible for testing areas that are part of your unit while the condominium corporation is responsible for testing areas that are part of the common elements of the building. If, for example, radon is a potential issue in the basement of your condominium townhouse, it may be up to you to test for it and report it to Tarion within your warranty timeline. If it’s in the parking garage of your high-rise, it’s likely up to the condominium corporation to test for it and report it within their warranty timeline. To determine which areas are part of your unit, review the registered declaration. If test results show radon levels are higher than 200 becquerels per cubic metre, the test results should be submitted to Tarion along with the applicable warranty form. Two important things to note when it comes to making a claim for radon remediation:

  • First: testing results need to be over a three-month period;
  • Second: whether you use a do-it-yourself radon test kit or a radon measurement or mitigation professional, both must be approved and certified through the Canadian National Radon Proficiency Program to be eligible for coverage under the new home warranty.

To learn more about radon, we encourage you to watch our video about Radon and Your New Home Warranty and you can visit the Health Canada website. If you are looking for do-it-yourself radon test kits or for a radon measurement or mitigation professional, you can contact the Canadian National Radon Proficiency Program by visiting www.c-nrpp.ca.

The goal of this blog is to provide you with general information about the warranty process by sharing real experiences from new homeowners. The blog should not be relied upon as legal advice. For privacy reasons, we will not address or resolve current cases in a public forum, so any comments or questions that are posted on this site that describe individual cases cannot be discussed. If you have a question about your warranty or Tarion generally, we would be pleased to discuss your issue, in the context of your particular circumstances and in confidence. We exercise reasonable care to avoid offensive, illegal or defamatory content from being posted, as well as comments that are intended solely for self-promotion or considered to be spam.