Radon-Ready New Buildings in Nova Scotia: Rough-Ins, Testing, and What the Code Actually Requires

Radon is the single most consequential indoor-air risk a residential development in Nova Scotia has to design around — and one of the few that is almost entirely solved at the foundation stage, before a slab is poured. The Government of Nova Scotia estimates that approximately 36.8% of homes in the province are expected to have radon levels exceeding the Health Canada guideline of 200 becquerels per cubic metre (200 Bq/m³) — more than double the national average of 17.8% [1]. For anyone deciding what to build on a Halifax-area parcel and how to build it, radon is not an afterthought to bolt on later. It is a line item in the feasibility study.

Helio is a computation-driven real estate development company in Halifax. We don't pour concrete — established builders do that — but we compute what a parcel can support, set the development program, and carry a project from raw land through to a completed building. Radon control sits squarely inside that program: it touches the foundation detail, the construction budget, the building-code compliance path, and the long-term operating risk of the asset. This article lays out what the rules actually require, what a rough-in does and does not buy you, and how the testing standard should be written into a development plan from the start.

As of 2026-06-23. Building-code editions, tier dates, and program figures below reflect the rules in force in Nova Scotia in mid-2026. Codes are revised on a published schedule; confirm current requirements against the primary sources cited before relying on them for a specific project.

What radon is, and why Nova Scotia is a high-risk province

Radon is a naturally occurring radioactive gas formed by the breakdown of uranium in soil and rock. It is odourless, tasteless, and invisible [1]. It seeps into buildings through cracks and openings in foundation walls and floors, drawn in by the pressure difference between the warm building above and the cooler ground below. Once inside, it can accumulate to levels that present a real health risk — and because you cannot see or smell it, the only way to know a building's radon concentration is to measure it [1].

The health stakes are not abstract. Health Canada attributes over 3,000 lung cancer deaths each year in Canada to radon exposure, and in Nova Scotia specifically the province attributes more than 100 deaths per year to radon [1]. For a multi-unit building, the exposure question scales with the number of households: a single building with elevated sub-slab radon can expose every ground-contact unit over the life of the asset. That is precisely the case where designing the problem out at construction — rather than retrofitting later — is the rational decision.

Nova Scotia's elevated risk is geological. The province publishes a radon potential / risk map so that landowners and developers can see how local bedrock and surficial geology translate into radon-release potential [1]. The map is a planning input, not a substitute for measurement: the provincial guidance is that testing is recommended regardless of the mapped risk zone, because radon concentrations vary lot-to-lot — even between adjacent properties — with soil composition and how a building is constructed [1].

What the building code actually requires

Nova Scotia adopts the national model codes. As of mid-2026, the province's building regulation adopts the National Building Code of Canada 2020 (NBC 2020), in force since April 1, 2025 under N.S. Reg. 198/2024, with the energy provisions phasing in by tier [2]. The Building Code Act and Regulations are provincial law, but permits, inspections, and occupancy approvals are administered municipally — in the Halifax region, by HRM's Planning & Development office [3].

The relevant radon provision lives in the soil-gas-control requirements of the code. The national radon rough-in approach was added to Canada's National Building Code in 2010 and has since been carried into provincial codes [4]. In practice, for new construction it requires:

• Sealing of radon and other soil-gas entry points in the foundation;
• A gas-permeable granular layer beneath the slab, so soil gas can move freely under the building rather than being forced up through it; and
• A radon rough-in "stub" — a short vent pipe rising from below the slab, capped — so that an extraction system can later be completed and, if needed, made active with a fan [4].

Two points matter for development decisions. First, the rough-in is a provision for future mitigation, not mitigation itself. The capped stub and the granular layer make it cheap and non-destructive to add an active system later; they do not, on their own, guarantee the building will sit below 200 Bq/m³. (British Columbia is the only province to mandate a full passive soil-depressurization system in radon-prone areas; the other provinces, Nova Scotia included, require the sealed and capped rough-in [4].) Second, the code does not require radon testing, and it does not require activating a fan during construction [4]. Those steps are left to the owner — which is exactly why a development plan has to specify them rather than assume the contractor will.

Rough-in versus a verified outcome

A radon rough-in is the right first move because it is overwhelmingly cheaper to install before the slab is poured than to retrofit afterward. But a rough-in is a passive setup by default — it relies on the natural "stack effect," the upward air movement created by temperature and pressure differences, to draw soil gas out through the vent pipe. In modern, well-air-sealed multi-unit buildings — exactly the energy-efficient envelope Nova Scotia's tiered energy code is pushing toward — that natural airflow can be too weak to reliably pull radon down to target levels. The fix is to convert the passive rough-in into an active soil-depressurization system: a fan draws radon from beneath the foundation through the existing pipe and exhausts it outdoors [5].

This is the standard, proven mitigation method. Health Canada and the Nova Scotia government both point owners to active soil depressurization as the primary approach — a pipe through the foundation floor and a fan that continuously draws sub-slab radon and releases it outside [5]. The reason developers should leave room in the design and budget for it is simple: it works regardless of weather or pressure conditions, where a passive system's performance depends on them. Supplementary measures — diligent foundation sealing, well-maintained HVAC and exhaust, crawl-space ventilation — help, but Nova Scotia's guidance is clear that they are complements, not standalone solutions, and that the only way to confirm a building is safe is to measure it [1][5].

The honest framing for a development program is therefore: install the rough-in for every ground-contact building; budget the contingency to make it active; and let post-construction testing decide whether that contingency is spent.

The testing plan: the part the code leaves to you

Because the code stops at the rough-in, the testing plan is where a development firm earns its keep. The standard is set by Health Canada and echoed by the province:

• Use a long-term test of at least 3 months. This is the Health Canada recommendation, and Nova Scotia's professional-testing guidance specifies that a certified measurement provider should conduct a long-term test [1][5]. Short-term tests (under a month) are not reliable for a decision because radon concentrations swing daily and seasonally.
• Test during the heating season. In Nova Scotia that period — roughly October through April — is when windows stay closed and the thermal stack effect pulls the highest indoor radon levels, so a heating-season measurement is the conservative one for a new building's first occupied winter.
• Test against the 200 Bq/m³ guideline. That is the Government of Canada radon guideline and the level Nova Scotia treats as the acceptable indoor ceiling; above it, mitigation is recommended [1][5]. It is a health-based guideline, not a legislated occupancy limit — which means a responsible owner acts on it whether or not a permit forces the issue.
• Test units, not just the building. In a multi-unit building, radon can differ markedly between ground-contact units and between stacks of the building. Unit-level long-term measurement is what actually confirms protection across the whole asset.
• Use a C-NRPP-certified provider for measurement and any mitigation. Nova Scotia directs owners to the Canadian National Radon Proficiency Program (C-NRPP) directory for certified professionals, both for long-term measurement and for installing an active mitigation system if results come back high [5].

Mitigation, if needed, is a known and bounded cost. Nova Scotia reports typical active-system installation in the $1,500–$3,000 range for an existing single home [5]; on a multi-unit building the per-system cost varies with building size and the number of sub-slab zones, but the economics still favour the building that already has the rough-in, granular layer, and entry-point sealing in place.

How radon fits into a Nova Scotia development feasibility study

The reason to address radon at the computation stage, rather than as a construction-site decision, is that it interacts with three things a feasibility study already has to resolve:

1. The compliance path. A radon rough-in is part of the soil-gas-control package the building must satisfy to pass inspection and obtain its permits. In Nova Scotia, an occupancy permit is required before a building (other than a single dwelling, shed, or pool) can be occupied, and in HRM that permit depends on a valid building permit and a passed final inspection [6]. Getting the foundation detail right the first time keeps that critical-path step from slipping.

2. The construction budget. The rough-in is inexpensive at the foundation stage and expensive to retrofit. Building it into the scope — and reserving a contingency for converting it to active if testing requires — is the difference between a predictable line item and an unplanned post-occupancy capital cost. Note that building permit fees themselves are modest and separate: in HRM, new residential construction of four units or fewer is charged per square metre of floor area (with a $31.25 minimum fee), and renovations or other construction are charged $6.88 per $1,000 of estimated construction value [7]. Radon control is a design-and-detail cost, not a permit-fee cost.

3. The long-term asset risk. For a purpose-built rental held for income, an elevated-radon building is a standing liability — to tenant health first, and to the owner's operating position second. A documented radon program (rough-in installed, long-term test completed during the heating season, mitigation activated if warranted) converts an invisible, open-ended risk into a closed, evidenced one. That is the posture a development firm should be able to put on the record for any building it brings to market.

None of this requires guessing. The geology is mapped, the guideline is fixed at 200 Bq/m³, the rough-in detail is specified by the National Building Code, and the testing standard is published by Health Canada. The work is in sequencing them correctly — install the provision at the foundation, measure the outcome over a full heating season, and act on the number. That sequence is what "radon-ready" actually means, and it belongs in the development plan from the day a parcel's program is set.

Frequently asked questions

If a building has a radon rough-in, does it still need to be tested? Yes. A rough-in is a provision that makes future mitigation easy and cheap; it is not proof that radon is below the guideline. Radon concentrations vary lot-to-lot, even between neighbouring properties, so the only way to confirm a building meets the 200 Bq/m³ guideline is a long-term test of at least three months, ideally over the heating season [1][5].

Is it cheaper to plan radon control during construction or to retrofit later? During construction. Installing the granular layer, sealing soil-gas entry points, and placing the capped rough-in stub before the slab is poured is far cheaper than cutting into a finished foundation. The forward-looking approach is to build the rough-in into the scope and reserve a contingency to make it active if post-construction testing shows elevated levels [4][5].

Does the National Building Code require an active radon fan in a new home? No. The code (via its soil-gas-control provisions, with the radon rough-in added nationally in 2010) requires the sealing, granular layer, and a sealed, capped rough-in pipe. It does not require radon testing or the activation of a fan during construction — those decisions are left to the owner, which is why they should be specified in the development and testing plan rather than assumed [4].

What does Helio actually do about radon on a project? As a development company, Helio sets the program and standards for a parcel and coordinates the team that delivers it. That includes specifying the radon rough-in at the foundation stage, writing the long-term, heating-season testing plan into the project, and reserving for active mitigation by a C-NRPP-certified provider if results require it — so the finished building's radon position is evidenced, not assumed [5].

Sources

1. Government of Nova Scotia — Make Sense of Radon (NS vs. national exceedance rates of 36.8% / 17.8%; 200 Bq/m³ guideline; >3,000 Canadian and >100 Nova Scotia radon-linked lung-cancer deaths per year; odourless/invisible gas; radon risk map; test regardless of risk zone). https://novascotia.ca/make-sense-of-radon/
2. Government of Nova Scotia — News Release, Province to Adopt 2020 National Building Codes (NBC 2020 in force April 1, 2025; tiered phase-in). https://news.novascotia.ca/en/2024/09/20/province-adopt-2020-national-building-codes
3. Halifax Regional Municipality — Building Code & Regulatory Information (provincial code, municipal administration of permits and inspections). https://www.halifax.ca/home-property/building-development-permits/building-code-regulatory-information
4. Health Canada — Radon action guide for municipalities: Building codes, bylaws and provisions (radon rough-in added to the National Building Code in 2010; sealing of entry points, granular layer, capped rough-in stub; BC full-passive vs. sealed-and-capped rough-in in other provinces). https://www.canada.ca/en/health-canada/services/health-risks-safety/radiation/radon/action-guides/municipalities/building-codes-bylaws-provisions.html
5. Government of Nova Scotia — Radon (Environmental Health) (long-term professional testing; 200 Bq/m³; active soil depressurization with a fan as the primary mitigation method; C-NRPP certified professionals; ~$1,500–$3,000 typical mitigation cost; NS radon risk map). https://novascotia.ca/nse/environmental-health/radon.asp
6. Halifax Regional Municipality — Application to Occupy (occupancy permit required before occupying a building, per the Nova Scotia Building Code Act; requires valid building permit and final inspection). https://www.halifax.ca/home-property/building-development-permits/commercial-mixed-use-building-permits/application-occupy
7. Halifax Regional Municipality — Permit Fees (Administrative Order #15) (per-square-metre new-residential fees and $6.88 per $1,000 of construction value; $31.25 minimum fee). https://www.halifax.ca/home-property/building-development-permits/permit-fees