Current as of August 2026. Building code requirements and municipal inspection practice change; confirm with your authority having jurisdiction.
Ontario, British Columbia and Quebec all require radon provisions in new residential construction, and the 2025 National Building Code raises the national baseline to a passive vertical stack. That has produced a practical problem nobody planned for: a mandatory building detail that almost no one is certified to specify or inspect.
There are roughly 21 CRNCH-certified professionals in all of Canada — the credential for controlling radon in new construction. It is by a wide margin the smallest certification pool in the Canadian radon industry, and demand for it is rising as codes tighten.
TL;DR: The inspection happens before the slab is poured, because most of what matters is buried afterward. It covers the gas-permeable layer, the soil gas barrier, the collector and pipe, sealing at the perimeter and penetrations, pipe routing and termination, and labelling. Get it wrong and the remedy is coring a finished basement.
Know which level you are building
CAN/CGSB-149.11-2024 defines the levels codes reference. Confirming which one applies is the first question on site, because the inspection differs:
| Level | What it is | Termination |
|---|---|---|
| 1a — rough-in | Gas-permeable layer, soil gas barrier and collector, connected to a solid pipe accessible above the finished floor | Capped and sealed inside the building |
| 1b — extended rough-in | As above | Pipe extends outside through a rim joist or sidewall |
| 2 — passive stack | Vertical stack through the building, venting by stack effect. No fan | Through the roof |
| 3 — active system | Fan added; active soil depressurisation | Per design (now in CAN/CGSB-149.12-2024) |
Province-by-province status: is a radon rough-in mandatory in my province?
The inspection window
This is the whole practical point. Most of the assembly is inaccessible once the slab is poured. The gas-permeable layer, the collector, the barrier and the below-slab pipe connection can only be verified before concrete.
Municipalities that operate radon inspection programmes — Hamilton, Guelph and Kingston in Ontario among them — typically set out builder and owner responsibilities covering slab perimeter sealing, soil gas barrier installation, rough-in pipe and granular material, and pipe capping and labelling before occupancy.
Practically, that means two inspection moments: pre-pour, for everything below and at the slab, and pre-occupancy, for pipe routing, sealing, capping and labelling.
What a pre-pour inspection covers
- Gas-permeable layer. Clean granular material of the specified depth and grading, or a proprietary gas-permeable layer system installed to the manufacturer's instructions. Fines and contaminated fill defeat the purpose.
- Soil gas collector. Perforated pipe or the proprietary equivalent, positioned to draw from the layer rather than sitting in it decoratively.
- Soil gas barrier. Continuous, lapped and sealed, with penetrations sealed. Assemblies in contact with the ground must resist soil gas leakage under the applicable code provisions.
- Riser pipe. Correct diameter for the jurisdiction — Ontario's 2024 Code specifies a minimum 100 mm (4″) pipe — solidly connected, supported, and accessible above the finished floor.
- Penetrations and perimeter. Service penetrations, the slab-to-wall joint, sumps and floor drains sealed. A perfectly installed collector under a leaky slab does not perform.
- Routing feasibility. For Level 2, confirm the vertical route through the building actually exists before framing commits it.
What a pre-occupancy inspection covers
- Termination. Correct for the level being built. BC requires the vent pipe to extend through and terminate outside the building; a capped Level 1a pipe terminating inside will not satisfy a code requiring 1b.
- Sealing and capping. The pipe capped and sealed where the design calls for it.
- Labelling. This is where builders most often fall short.
Labelling
C-NRPP publishes labels developed in accordance with the CGSB standards, with distinct labels for Level 1 rough-in, Level 2 extended rough-in, and Level 3 active systems, plus electrical box labels. C-NRPP recommends bilingual labelling in accordance with the standard's recommendations — and because of the text volume, that generally requires two labels.
Labels matter for a reason that outlasts the build: the next owner, the next inspector and the next contractor need to know what is in the wall. An unlabelled capped pipe in a basement is an unsolved puzzle in ten years.
The credential problem
C-NRPP certifies Controlling Radon in New Canadian Homes (CRNCH) for professionals who specify, install, inspect and maintain rough-in systems, including active-ready and passive systems without fans. It is a short certification — a four-to-six-hour course and a 50-question exam, currently bundled with mitigation certification for renewal purposes.
With roughly 21 holders nationally against requirements already in force in Ontario, BC and Quebec and a national code raising the baseline, the mismatch between the requirement and the expertise available to implement it is likely to widen before it narrows. For building officials, that means inspecting a detail the trades are still learning. For builders, it means the person who knows the detail is scarce and worth booking early.
What the inspection does not establish
A passed inspection means the assembly was built correctly. It does not mean the finished building will be below 200 Bq/m³.
Radon levels cannot be predicted before a building is occupied — two homes on the same street built to the same plan can test very differently, depending on the soil beneath that foundation, pressure differences in the structure and how occupants live in it. Every Canadian code provision addressing radon requires preparation rather than promising a result. Quebec is the exception that proves the point: it also requires radon test results to be submitted to the authority having jurisdiction.
Health Canada's position is unchanged: test after occupancy, with a long-term test of at least three months during the heating season.
A short checklist
- Confirm which CGSB level your jurisdiction requires for this permit.
- Book the pre-pour inspection into the schedule, not around it — concrete does not wait.
- Verify granular material and barrier continuity before anyone calls for the pour.
- Confirm pipe diameter against the local code, not habit.
- Confirm the vertical or sidewall route before framing.
- Label before occupancy, bilingually.
- Tell the owner to test after they move in, over a full heating season.
Common questions
When does a radon rough-in get inspected?
Before the slab is poured for everything below and at the slab, and again before occupancy for routing, sealing, capping and labelling. Municipal programmes vary; confirm locally.
What size pipe is required?
It depends on the jurisdiction. Ontario's 2024 Building Code specifies a minimum 100 mm (4″) pipe for the rough-in. Confirm with your authority having jurisdiction.
Who is qualified to inspect a rough-in?
Building officials inspect to the code in force. C-NRPP's CRNCH credential certifies professionals to specify, install, inspect and maintain rough-in systems; roughly 21 professionals in Canada hold it.
Does a rough-in mean the home won't have a radon problem?
No. It means the fix will be simple and inexpensive if one is needed. Only a long-term test after occupancy establishes the actual level.
Do labels have to be bilingual?
C-NRPP recommends bilingual labels in accordance with the standard, and notes that the text volume generally requires two labels.
Read next
Rough-in requirements for builders · Is a rough-in mandatory in my province? · Canadian building codes and radon · New-home warranty coverage
RadonTest.ca provides testing logistics and laboratory submission. We do not perform radon mitigation, we do not install or inspect rough-in systems, and we do not interpret health risk — Health Canada is the health authority on radon in Canada. This page is not legal advice, nor engineering or code-compliance advice; your authority having jurisdiction is the governing source.
Sources
CAN/CGSB-149.11-2024, Radon control options for new buildings; CAN/CGSB-149.12-2024; National Research Council Canada, National Building Code of Canada 2025; 2024 Ontario Building Code (O. Reg. 163/24) and MMAH Supplementary Standard SB-9; 2024 British Columbia Building Code, Subsection 9.13.4; Code de construction du Québec; Health Canada, Radon action guide for municipalities; C-NRPP radon labels and professional resources; C-NRPP Technical Bulletin, Radon and New Construction.