Canadian Contractor

John Bleasby   

‘Sealing the deal’ for a dry, mold-free basement

Canadian Contractor

Experts debate personal use vs. income stream, but all agree on avoiding common errors

Renovating a basement for personal use or as a potential rental income stream makes tremendous sense for homeowners. Paul Maranger, a high-end real estate broker with Sotheby’s International Realty Canada recently told BNN News “Basements today have a very high return compared to previous years. If your basement reads storage, you pull away from value.”

Personal use or rental income; the aim is the same
Some homeowners like the idea of a subterranean hideaway, perhaps with a home theatre, a pool table, a bar, or exercise equipment. The possibilities for this extra space are endless.

A better way to insulate and finish basement walls.

A better way to insulate and finish basement walls.

Property renovation experts like Scott McGillivray, host of TV’s Income Property, see a basement as a route to financially viable home ownership. In the same BNN article he explains “If you’ve got two houses side-by-side for $500,000 and one has an income suite, someone who is qualified for a $400,000 mortgage based on their income can’t buy the one without the income suite. The income suite may add $1,200 or $1,500 per month to their qualified income. Now they can qualify for financing on the property,”

Out of sight should not mean out of mind
Key in both cases is a basement renovation is using the correct materials. In today’s world of improved building material choices it means avoiding common errors concerning mold and moisture control, the ‘dream-killer’ of basement renovations. Sadly, it is often not seen until it has become a serious problem.


Here are the some of the most common mistakes:

Using standard wood studs on basement walls
Condensed moisture that forms between the cold foundation walls and the warm interior finishing will be absorbed by standard wood studs and turned to mold. Use inorganic materials instead.

Plastic vapour barriers
Plastic makes a bad situation even worse, particularly when combined with popular fibreglass batt insulation. Moisture trapped between foundation wall and the vapour barrier is absorbed by the batts, reducing their insulation effectiveness and allowing mold growth. Use rigid foam or spray insulation instead.

Using batts and plastic vapour barrier on ceilings
Sound insulation is important in the basement, whether used for personal or rental purposes. Fibreglass batts and vapour barrier in the ceiling are subject to the same risks as on the walls. A 3” layer of spray foam insulation foils mold and moisture.

Using spray foam on basement ceilings reduces noise and significantly reduces the chance of moisture and mildew

Using spray foam on basement ceilings reduces noise and significantly reduces the chance of moisture and mildew

It almost goes without saying that moisture that dribbles down walls will find its way to the floor. That’s why a properly conceived sub-floor using underlay like DMX 1-Step is critical for completing the moisture ventilation package of a renovated basement.

The result is a comfortable, healthy and warm below-grade living space that will deliver true long-term equity value.


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1 Comment » for ‘Sealing the deal’ for a dry, mold-free basement
  1. Kyle says:

    I’m a contractor based out of Toronto and there have been many times where I’ve gone on a quote for a basement renovation and the homeowner doesn’t want to update the existing builder insulation with vapour right on the concrete wall with the proper building method. As contractors it’s our job to inform the homeowner of proper building practices and spend the money where it counts. Either finish your basement properly of don’t do it at all because there will be tons of mould issues in the future.

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