Radon Mitigation in Steinbach

Steinbach sits southeast of Winnipeg on sandier glacial deposits rather than the dense lacustrine clay of the Red River valley. That difference matters under a house. Sandy and gravelly soils drain well, so surface water is less likely to pond against a foundation, but they also transmit groundwater freely. When the regional water table rises during melt or after a sustained wet spell, it can come up through a crawlspace floor instead of running down the backfill. Homeowners here are often surprised by water appearing in a space that has never had a drop in a decade.

As the largest community in the southeast, Steinbach has a broad range of housing: pre-war homes near the core, large mid-century neighbourhoods, and substantial new construction on the edges. Crawlspaces appear throughout, most commonly under additions, sunrooms and secondary structures, and in older homes as the original foundation type. The recurring issues we document are condensation-driven rather than flood-driven in most of the city — summer humidity entering through vents, condensing on cool surfaces, and feeding mould on joists and the underside of the subfloor while batt insulation holds the moisture in place.

Because the soil drains, the right system here often differs from what we would install in Lorette or St. Adolphe. Interior drainage may be less critical, but a well-sealed floor barrier is more important, since a permeable soil column under the house moves both moisture vapour and radon upward efficiently. Manitoba has some of the highest indoor radon readings in the country, and a crawlspace with a bare or poorly sealed floor is the usual entry route. We test, seal properly, and where readings warrant it, install active sub-membrane depressurization alongside the encapsulation.

Steinbach calls have a different character from the clay communities, and it reflects the soil. Homeowners describe crawlspaces that have never had standing water but smell musty every summer, with condensation visible on ductwork and cool surfaces in July. That is a vapour and condensation problem rather than a drainage one, driven by humid outdoor air entering a vented space and meeting cool framing. The other common call is from owners who have tested for radon and found an elevated result.

Permeable soil has a specific consequence worth understanding: it transmits both water vapour and soil gas upward very efficiently. In clay, a poorly sealed floor is a moderate vapour source. In sand and gravel, it is an open channel. That makes a properly sealed, fastened and terminated membrane more important here than in the clay communities, not less — and it makes radon testing genuinely worthwhile given Manitoba's provincial readings.

Our first recommendation for a Steinbach-area property is usually to test for radon before sealing, so the collection pipe and permeable layer can be installed under the membrane rather than retrofitted through it afterward. Alongside that, sealing the floor and walls properly and moving insulation to the perimeter addresses the summer condensation that drives most of the mould we find here. Interior drainage may be unnecessary — we will tell you if the readings say so.

Radon is a naturally occurring radioactive gas produced by the decay of uranium in soil and rock. It is colourless and odourless, it moves upward through soil, and it enters buildings through any opening in contact with the ground. Health Canada identifies it as the second leading cause of lung cancer after smoking, and sets a guideline of 200 becquerels per cubic metre for indoor air, recommending remedial action above that level. Manitoba consistently records some of the highest residential readings in Canada, which makes this a local issue rather than an abstract one.

A crawlspace is the most efficient radon entry point a house can have. Where there is exposed soil, or a thin unsealed membrane, soil gas moves into the space essentially unimpeded — and from there into the living area, because the stack effect pulls air upward through a house continuously during the heating season. Our long heating season means that pressure difference operates for a large part of the year. A house with a sealed basement slab but an open crawlspace under an addition can still have substantially elevated levels.

Testing has to come before mitigation, and it has to be done correctly. A long-term test of at least three months, ideally during the heating season when windows are closed and the stack effect is strongest, gives a representative result. Short-term tests are useful as a screening indicator but fluctuate too much to base a decision on. We will arrange or guide testing, and we would rather you test first than buy a mitigation system you may not need — though in a crawlspace with exposed soil, sealing the floor is worthwhile on moisture grounds regardless of the radon number.

Where mitigation is needed, the standard approach in a crawlspace is active sub-membrane depressurization. A sealed membrane is installed across the floor and up the walls — the same membrane used for encapsulation, which is why these two projects belong together — and a dedicated fan draws continuously from beneath it through a perforated collection pipe, venting above the roofline. That negative pressure under the membrane captures soil gas before it can enter the space. The system is simple and highly effective, but it depends entirely on how well the membrane is sealed, which is why installation quality matters more than equipment selection.

Post-mitigation verification is not optional in our view. After the system is running and the building has returned to normal operating conditions, the space and the living area should be retested to confirm the reduction. We also label the system, explain what the manometer reading means, and tell you what to check — because a mitigation fan is a mechanical device that will eventually fail, usually silently. A system nobody monitors is a system that may have stopped protecting you years ago.

Pressure and building dynamics explain why two apparently identical houses can test very differently, and why your neighbour's result tells you nothing about yours. Radon entry depends on the pressure difference between the soil and the building interior, and that depends on stack effect strength, exhaust appliances, mechanical ventilation balance, wind, and how tight the building is. A house with powerful kitchen and bathroom exhaust and no make-up air runs at a greater negative pressure, and draws correspondingly more soil gas. This is also why sealing work and mechanical changes can shift a reading in either direction, and why testing after any significant envelope work is sensible.

System design details separate a mitigation that works from one that merely hums. The collection point beneath the membrane needs a permeable layer — clean gravel or a drainage mat — so the fan can draw from the whole footprint rather than a single spot. The fan has to be sized to the soil's permeability and the area served: too little suction leaves parts of the footprint uncaptured, too much wastes energy and can pull conditioned air if the membrane has gaps. The exhaust must terminate above the roofline and away from windows and air intakes. And the pipe needs a manometer, so the system reports its own status.

Timing relative to encapsulation is the practical advice we give most often. If you are sealing a crawlspace for moisture reasons and you have not tested for radon, test first. The collection pipe and gravel layer belong under the membrane, installed before it goes down; retrofitting them means cutting open a barrier you just paid for and compromising its continuity. A long-term test takes three months, which is usually compatible with planning a project anyway. If the number comes back low, you have lost nothing but gained a documented baseline. If it comes back high, you have saved yourself from doing the job twice.