What Humidity Should a Basement Be in Canada?

Who this guide is for

This guide is for homeowners whose basement feels damp, smells stale, shows condensation, or who simply want to know whether their humidity is in a healthy range. It explains how to measure and interpret humidity. It is not a professional inspection, and it does not diagnose mould or health problems.

Measure first: how to read a hygrometer

A hygrometer (humidity meter) shows relative humidity (RH) as a percentage. Inexpensive digital models are widely available and are the simplest way to replace guesswork with numbers.

• Place it at roughly chest height in the main basement area, away from the dryer vent, bathroom, furnace, exterior doors and direct sunlight.
• Let it settle for at least an hour after moving it before trusting the reading.
• Record the reading at the same times each day for at least a week, and note the weather and anything unusual (laundry, showers, a humid day).
• If you have a second meter, compare readings side by side. Budget meters can differ by a few percentage points, so look at trends rather than a single number.
• Take extra readings in the spots you're worried about — a storage room, behind boxes against an exterior wall, or under the stairs.

What your readings mean

• Mostly between 30% and 50%: generally within the range Health Canada recommends. Keep monitoring seasonally.
• Regularly above 50%: worth investigating. Persistent high humidity increases the chance of condensation and mould growth on cool surfaces.
• Regularly above 60%, or visible condensation, dripping, or water marks: investigate the moisture source soon rather than just masking it.
• Below 30% (common in Winnipeg winters): the air may feel dry, but this is a comfort issue more than a basement moisture problem.

Why basements get humid

• Summer: warm, humid outdoor air enters the basement and cools against concrete, raising relative humidity.
• New or recently poured concrete: new homes can release a significant amount of moisture from concrete during their first years.
• Indoor activities: laundry, an unvented or poorly vented dryer, showers, cooking, aquariums and plants.
• Ventilation that isn't running or is poorly balanced, including an HRV that is switched off or has clogged filters.
• Water from outside: grading that slopes toward the house, downspouts discharging close to the foundation, or foundation cracks.

Check the moisture source before buying anything

• Walk the outside of the house: do downspouts discharge well away from the foundation, and does the ground slope away from the walls?
• Look at basement walls and the floor-wall joint for damp patches, water lines, stains or white mineral deposits.
• Check that the dryer vents outdoors and its duct isn't disconnected or crushed.
• Confirm bathroom fans and any HRV are working and actually being used.
• Note whether humidity spikes after rain, after laundry, or only in summer — the pattern points to the cause.

What a dehumidifier can — and can't — do

If your readings stay above 50% and you've ruled out obvious water entry and indoor sources, a dehumidifier is a reasonable next step, especially in summer. It removes moisture from the air. It does not stop water coming through walls or floors, fix drainage, or remove existing mould.

• Features to research: a built-in humidistat so you can set a target, continuous drain or pump options if you don't want to empty a bucket, and an ENERGY STAR certification for running costs.
• Size the unit to your space and conditions — a dedicated sizing guide is coming soon.
• Keep your hygrometer running after you start a dehumidifier so you can confirm it's actually bringing readings down.

When to call a professional

• Water is entering the basement, the sump pump runs constantly, or there is standing water.
• You see mould growth larger than a small patch, or it keeps coming back after cleaning. Health Canada's guidance explains when professional help is recommended.
• Foundation cracks are widening, leaking, or appear alongside doors or windows that are sticking.
• Humidity stays high despite reducing indoor sources and running a dehumidifier.

Winnipeg and Manitoba notes

Manitoba's cold winters make condensation on windows, rim joists and exterior walls a common sign that indoor humidity is higher than the cold surfaces can handle. If you see frost or condensation in winter, lowering humidity toward the 30–35% end of the range and making sure ventilation runs usually helps. Summer is when basement humidity in Winnipeg most often climbs.