How to choose basement flooring in Ottawa

Key takeaways

• If any part of the slab is below ground level, the floor is below grade, walkouts included, and moisture can move up through the concrete.
• Fix leaks and dampness before anything goes down, and keep the humidity between 30% and 50%, as Health Canada recommends.
• Rigid-core vinyl, engineered wood (floated or glued, never nailed) and tile all work below grade. Makers don’t allow solid hardwood there.
• Before finishing, test for radon over at least 91 days of the heating season, and look at the City’s rebates for a backwater valve and sump pump.

01

What makes a basement floor different?

Flooring makers draw the line simply: a concrete slab is below grade when any part of it is below ground level. A basement with a walkout still counts. The ground on the other side of the concrete holds moisture, and the concrete doesn’t stop it moving through.

Natural Resources Canada’s advice for basement floors deals with that directly: put a moisture barrier on the floor, or seal it, for comfort, for moisture control and for radon reduction. Most of this guide follows from that one idea.

02

Is the basement dry enough to finish?

Answer this before choosing a floor. Natural Resources Canada warns against finishing a basement from the inside while it has moisture problems, because interior finishes hide moisture problems as they develop. A new floor is a finish. The signs it lists:

• Leaks: water coming in through the walls or the floor.
• Dampness: concrete that stays damp to the touch.
• Efflorescence: white, powdery deposits on the concrete, left by water moving through it.
• Blistering paint on the foundation walls.

Health Canada’s advice on mould comes at it from the other side: fix the underlying water problem first. Then keep the air in range. It recommends relative humidity between 30% and 50%, with a dehumidifier running in the basement if that’s what it takes.

Last comes the slab itself. In one maker’s words, below-grade slabs “must be carefully tested”, and each maker names its own test and limit. On every floor we lay, the base is checked for moisture, level and flex before anything goes down.

03

Which floors work below grade?

So the real choice is between three floors, and what separates them is less the surface than what has to go underneath. Each one handles the slab its own way:

04

What goes between the slab and the floor?

First, a flat surface. One rigid-core vinyl maker’s limit is 3/16 inch over 10 feet. On the floors we lay, high spots are ground down and low ones self-levelled before the floor goes in. Then the layer that deals with moisture, which depends on the floor:

• Under vinyl: a 6‑mil plastic sheet. One rigid-core maker requires it on all concrete floors, even with a pad already attached to the plank, and voids the warranty without it.
• Under engineered wood: a pad with a built-in moisture barrier if the floor floats, or a vapour-control system from the adhesive maker if it’s glued.
• Under tile: an uncoupling membrane bonded to the slab. Its maker says the space under it gives moisture and vapour from the concrete a route to escape.

05

Should you test for radon first?

Yes, and finishing is what makes it matter. Health Canada’s guideline for radon, 200 Bq/m³ averaged over a year, applies to the parts of a home where someone spends more than 4 hours a day. An unfinished basement is left out. A finished one, with a family room or a bedroom, is in.

Health Canada’s method takes time: a long-term test of at least 91 days, during the heating season, on the lowest lived-in level of the home. If a basement is to be finished over the winter, the autumn is the time to start the test. Sealing the floor or putting a barrier over it, which the flooring needs anyway, is also one of the things NRCan lists for reducing radon.

06

How do you protect a finished basement from flooding?

No floor can stop water backing up through a drain. For that, the City of Ottawa’s Residential Protective Plumbing program rebates part of the cost of backwater valves and sump pumps with battery backup, up to the amounts below or the cost of the work, whichever is less.

• Age of the house: built before 1 January 2004 for a storm backwater valve, or before 1 January 2012 for a sanitary one.
• Permit first: the work needs a building permit before it starts, and a City inspection when it’s done.
• Timing: since 1 July 2026, the work must be finished and the application in within 18 months of the permit’s issue date.
• New devices only: repairs and replacements of existing devices aren’t covered.

07

Does it need a permit, and how long does it take?

The floor on its own doesn’t: new flooring is on the City’s list of work exempt from a building permit. Finishing the rest of the basement is a separate question, and our guide to which renovation work needs a building permit in Ottawa sets out where the line falls. If the plan is a separate unit with its own entrance, the rules in the legal basement guide come before any flooring decision.

Flooring typically takes 3 to 4 weeks on site, depending on the size of the area and how much the slab needs. Floating vinyl and click engineered floors can be walked on straight away; glued floors and tile within a day, because we use rapid-setting adhesive and grout. For how that fits with the rest of the work, see how long each stage of a renovation takes. A basement floor is often one part of a larger home renovation in Ottawa, and the checks above are worth doing before any of it starts.