Radon Mitigation in East Kildonan

East Kildonan sits on the east bank of the Red River with housing concentrated between roughly 1910 and 1960. It is an older, settled area, and the foundations reflect their age: early concrete and block, shallow by current standards, with no original damp-proofing or vapour control. Homes close to the river deal with a high water table; homes further east deal primarily with clay heave and poor surface drainage.

Crawl areas here come in both forms — original foundations under smaller or older houses, and additions built over many decades. The condition we find most often is a shallow space with bare soil, open vents, and framing that has spent decades in the damp range. Mould on the underside of the subfloor, rust on hardware and ducting, soft wood at sill plates and the musty odour that follows air upward into the living space are all routine. Where additions sit on shallow piers, seasonal frost movement has usually racked the framing as well.

Our work starts with identifying the water source and the founding depth, because those two facts determine everything else. Exterior grading and downspout corrections remove a surprising share of the load. Interior drainage and a properly discharged sump handle the rest where groundwater is active. Support is brought to stable bearing where piers have been cycling. Then the space is encapsulated with reinforced material sealed to the walls and penetrations, insulated at the perimeter, and monitored for humidity through a full seasonal cycle.

East Kildonan calls often come from homes close to the river with early concrete or block foundations and no original damp-proofing. Owners describe a smell that carries upstairs, mould on the underside of the floor, rusted hardware and ducting, and damp soil that never seems to dry. Further east, the calls shift toward frost-heaved addition piers.

Our first recommendation is to establish the water source and the founding depth, since those two facts drive everything else. Exterior grading and downspout correction removes a meaningful share of the load cheaply; interior drainage handles active groundwater. Support is corrected where piers have been cycling, and only then is the space sealed and insulated.

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.