Radon in Quebec Condos: Duties and Testing

Radon is a natural, odourless and invisible gas that can infiltrate residential buildings, including divided co-ownerships. In Quebec, the issue raises legitimate questions for syndicates and boards of directors (boards): what are your obligations, how should you test, and what should you do if levels are too high? (Information current as of 2026-06-21.)

In this article, we clarify your responsibilities, propose a testing approach suited to condos, and present realistic mitigation solutions to protect occupants, the building and the syndicate’s budget.

Radon and co-ownership: the essentials

• Radon comes from the soil and infiltrates through cracks, joints, sump pits and penetrations beneath the slab, particularly on lower levels and in areas in contact with the soil.
• Elevated levels can affect long-term health. Syndicates must therefore address the risk from a prevention, maintenance and sound governance perspective.
• As of today, there is no general provincial obligation requiring radon testing for all residential divided co-ownerships. However, the syndicate has a duty to preserve the building and ensure the maintenance and safety of the common portions (see the Civil Code of Quebec, articles relating to the syndicate’s role). See the Civil Code on LégisQuébec.
• The Quebec Construction Code incorporates technical requirements inspired by the National Building Code to reduce the risk of infiltration (provisions for mitigation in newer construction). Refer to the Regie du batiment du Quebec (RBQ) for applicable requirements and work compliance.

What are the syndicate’s and board’s obligations?

The syndicate, represented by the board of directors, must preserve the building, administer the common portions prudently and diligently, and ensure the safety of occupants and visitors. In practice, this involves:

• Assessing reasonably foreseeable risks, including radon, especially in buildings with spaces in contact with the soil (garages, crawl spaces and finished basements).
• Planning preventive maintenance and documenting interventions in the maintenance logbook (EUC) and the co-ownership register.
• Informing co-owners, presenting an action plan at the annual general meeting and having the syndicate’s decisions recorded in the minutes.
• Ensuring, where necessary, the compliance of work and licensed contractors (see the Regie du batiment du Quebec (RBQ)).

Legal basis to review and paraphrase for your lawyers:

• The syndicate’s role and powers (preservation, maintenance and administration) are provided for in the Civil Code of Quebec (for example, articles concerning the syndicate’s mandate and the maintenance of the common portions). References are available on LégisQuébec.

Even without a general testing obligation, reasonable diligence recommends assessing the risk and taking action when a problem is identified, particularly when elevated levels are measured in units or common portions.

How to organize radon testing in a divided co-ownership

The testing strategy must reflect the reality of a divided co-ownership (private portions versus common portions) and aim for sufficient coverage. Here is a practical approach.

Recommended steps

1. Planning by the board
   • Appoint a board representative and approve a minimum testing budget (common expenses).
   • Define a protocol: duration, targeted locations, schedule and suppliers.
   • Prepare information for co-owners (objectives, confidentiality and access to units).
2. Choosing detectors
   • Give preference to long-term detectors (approximately 3 months), particularly during the heating season.
   • Keep short-term detectors for specific investigations (e.g., rapid validation before work), without replacing long-term measurement.
3. Where should you test?
   • Private portions: prioritize units at ground level, on a slab, above garages and those with floors in contact with the soil.
   • Common portions: mechanical rooms, crawl spaces, basements, corridors on the lower level and spaces adjacent to known cracks.
   • Document the exact location, height and exposure duration for each detector.
4. Communication and logistics
   • Notify co-owners and occupants in writing, explain the procedure and provide clear instructions.
   • Obtain the necessary access to units; record refusals or delays in the register.
   • Set up a single point of contact (management or a board member) for questions.
5. Analysis and interpretation
   • Have the analysis performed by a recognized laboratory and obtain a consolidated report.
   • Interpret the results at the building level. An elevated result in one unit warrants an investigation into infiltration pathways (cracks, sump pits and service penetrations). A common pattern may involve work on common portions.
6. Documentation
   • Archive the results and correspondence in the register, update the maintenance logbook (EUC) and prepare a summary for the annual general meeting.
   • When action is required, add the item to the agenda and have the required resolutions adopted; include them in the minutes.

For support with planning and communication, see our Administrative management page and our operations management offering.

Mitigation and work: solutions, responsibilities and budget

When concerning levels are measured, the objective is to reduce the concentration, ideally below the generally recognized Canadian guideline (200 Bq/m³). Solutions vary depending on the cause and the building’s configuration.

Typical solutions

• Targeted sealing of cracks, construction joints, conduit penetrations and access hatches.
• Sealing and installing airtight covers on sump pits; adding a drain or membrane where appropriate.
• Sub-slab depressurization (a soil suction system) in affected areas, with one or more collection points.
• Adjusting and maintaining ventilation (e.g., HRV), balancing airflow and improving exhaust ventilation in garages.
• Managing differential pressures (sealing mechanical shafts and fire-rated joints).

Who pays for what?

• Common portions (foundations, common slab, garages and shared crawl spaces): work is paid for by the syndicate through common expenses; financing comes from the operating budget, the contingency fund or special assessments, depending on the scope and nature of the work.
• Private portions: if an intervention is limited to strictly private elements and does not result from a defect in a common portion, the costs may fall to the co-owner concerned, subject to the declaration of co-ownership and the by-laws of the immovable.

Good governance practices

• Use contractors who hold the appropriate licences and comply with applicable standards. Consult the Regie du batiment du Quebec (RBQ) to verify licences and technical requirements.
• Plan a control re-test after the work (generally 3 months) and provide for a periodic follow-up campaign (e.g., every 5 years or after major building-envelope or foundation work).
• Update the maintenance logbook (EUC) and maintenance schedule; adjust financial planning accordingly. For the budget component, see our financial management services.

Useful resources and industry references:

• RGCQ — Good co-ownership practices (governance, communication and maintenance).
• OACIQ — Radon — Information related to real estate transactions and disclosure.
• LégisQuébec — Civil Code of Quebec — The syndicate’s role, maintenance and common expenses.
• Regie du batiment du Quebec (RBQ) — Quebec Construction Code, compliance and licences.

Governance, declaration of co-ownership and communication: integrating radon into your practices

• “Radon” policy: the board can propose an internal policy governing periodic testing, communication of results, access to units and cost-sharing. This policy can be incorporated into the by-laws of the immovable, subject to the declaration of co-ownership and the required majorities.
• Declaration of co-ownership and by-laws: review existing clauses concerning sanitation, access for work and cost allocation; amend them where necessary with the assistance of legal counsel.
• Annual general meeting and minutes: present the findings, options and recommendations; have the necessary budget allocations approved; keep clear minutes.
• Transparency: provide co-owners with an accessible summary while respecting the confidentiality of unit-specific data where appropriate.
• Planning: incorporate follow-up into the maintenance logbook/EUC and long-term planning (contingency fund and common expenses).

For examples of processes and communications, visit our blog and the About us section.

FAQ — radon in divided co-ownerships

Q1. Is the syndicate required to conduct radon tests?

As of today, there is no general obligation requiring testing for all residential divided co-ownerships in Quebec. However, the syndicate has a duty to preserve the building and ensure a safe environment, which justifies testing when the risk is plausible or after work that could alter infiltration pathways.

Q2. Who bears the mitigation costs?

Corrective work related to common portions (e.g., depressurization beneath a common slab or sealing a sump pit connected to the drain) is usually paid for by the syndicate. Strictly private interventions may fall to the co-owner, depending on the declaration of co-ownership and the by-laws. Financing may come from the current budget, the contingency fund or special assessments, depending on the scale of the work.

Q3. What happens if only one unit exceeds the guideline?

The board should investigate the source. If the infiltration comes from or is aggravated by a common portion (a crack in the common slab or negative pressure related to the garage), action by the syndicate is warranted. Otherwise, the syndicate can support the co-owner with a localized solution while planning additional checks in neighbouring units.

This article provides general information and does not constitute legal advice. Consult a lawyer or notary for your situation.

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