Canadian Contractor


Code changes that could save thousands Part 2: The need for innovation: slab on grade

Why do we build foundations a minimum of 4 feet below grade in Canada?


By Paul Duffy, M.A.Sc., P. Eng.

Last issue, Duffy pointed out why the regulatory industry makes innovation so expensive. In this issue, he uses the real-world example of Slab on Grade construction to illustrate the roadblocks to innovation and how they create real world problems.

There are many factors driving the need for innovation, ranging from energy and environmental imperatives to limits on raw material resources, or simply finding more effective ways to build, reduce cost or improve affordability, etc. We have all seen the workings from researchers, policy analysts, lobbyists and the like. To continue building without new systems and technology advances is nothing short of crazy.

To illustrate the point, it really takes a couple of examples.

Slab on Grade Construction

Firstly, consider slab-on-grade construction.  Why do we build foundations a minimum of 4 feet below grade in Canada? The answer is simple—to get footings below the frost line. But, what if you insulate the footings so that frost does not penetrate the ground, how far down do you need to go?  Well the Code does not tell you.

No big deal… you have to go down four feet, so insulate the walls and turn the basement into living space. It’s not the best solution—moisture ingress can be an issue and the view underground is less than ideal, but, creating living spaces below grade does kind of turn a lemon into lemonade, as the expression goes.

But wait, suppose you are building a home for seniors, or someone who has mobility problems. You don’t want a house with stairs. You can add an elevator, I suppose, with all the associated costs. Or, you can simply build a slab-on-grade house.  But that is not described in the Code particularly well, so you will need to hire an engineer, and because the Code doesn’t help much, be prepared for delays getting a building permit because most municipalities will balk at a house that does not have a basement or at least perimeter footings that go below the “frost line”.

Not convinced that this is important to you? Slab-on-grade houses are not common in this part of the world so is it a real issue or am I just making a mountain out of a molehill? How about building a house near a lake or river… chances are you will hit the water table close to the surface of the land… do you really want to go down 4 feet to avoid frost? Do you want to drain the lake?  I have seen lots of folks try to solve the problem by moving in soil, sometimes hundreds of cubic meters of soil to raise the grade and protect their foundation.  You can easily see lots of situations where tens of thousands of dollars are added to the cost of a construction project because the builder needs to place footing below the frost line. Does that sound more sensible than a slab-on-grade foundation?

Still not convinced? Maybe you simply want a basement walk-out at the rear of the home. If there was a simple solution that could save you thousands of dollars, wouldn’t you want to hear about it or at least have that option?

The interesting thing is that most of the world builds without basements. Yes, it is true that you don’t need to go down below the frost line in places like Florida or Texas so the way they build might not necessarily work in Canada.  But consider the way they build in places like Sweden. Swedes often build with insulated slab-on-grade construction and they have done so for years. Here is the crazy part…their Code was based on research partly done right here in Canada!  In the 1960’s, a Professor by the name of Fred DeLory at the University of Toronto did pioneering research into insulated slab-on-grade construction and his work made its way into Nordic Building Codes, but the Codes for foundation design right here in Canada never did change. It’s hard to say whether we should be proud or embarrassed.

It’s a pretty important (and ironic) gap in our Codes but is it the only area where we are lagging? Sadly, no it is not.

To read part 1 of this series, go here. Next issue: Roof venting

Questions and comments on this article can be addressed to Paul Duffy and Associates Inc.




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13 Comments » for Code changes that could save thousands Part 2: The need for innovation: slab on grade
  1. Jay says:

    With the amount of money invested in homes, do you really want to cheap out on the one item that could destroy the equity in that home? I think not. Frost heaving is an issue in Canada almost everywhere except a few places like Southern Ontario or Vancouver Island. I live in Fort McMurray and the winters here can be brutal. I had a neighbour who had frost heave problems simply because there was a slope at the back of his lot. Even worse is people pushing this design add extreme amounts of insulation to reduce heat loss. What keeps the ground from freezing?

    By the way, yes, I’m an engineer.

  2. Jeffrey Daigneault says:

    In the house I lived in, our basement walls would freeze all the time, you could see frost on concrete. My father attempted finishing our basement soon after we installed a gas fireplace in the corner above in our family room. Every winter after we installed that fireplace, the basement leaked, or had some type of water build up in that corner. The basement was unfinished mind you.

  3. Warren Tutton says:

    I have formed a group here in Niagara on the Lake that wish to downsize from there large homes and build a community of about 10 to 15 1,400 to 1,500 sq ft homes with no basements. I am having some difficulty in convincing them that there is a void in the system for this type of housing. We are all seniors and do not want the next step in our lives to be herded into a 900 sq ft assisted living block where one can not bring many of there life long treasures with them ( paintings, furniture, etc). Do you have any factual data to support my position?
    Surely there is new technology that makes it more cost efficient, to say nothing for ongoing costs, because you are not heating a basement you hardly use. Appreciate your input. Cheers, Warren

    • Leslie says:

      Warren, I’m most interested in your plans and agree completely that this type of housing is missing… there are many seniors or folks with mobility/accessibility challenges who are capable of independent living and their needs are not being met. While not at retirement stage yet, we are thinking of our future, possibly in the Niagara area. I have become very interested in the “pocket neighbourhood” concept, which serves a broad demographic, in my opinion: . I think this type of housing requires builders & City planners to be more creative and to shift from being so profit/tax revenue driven to being more community-minded. My experience with our local City administrators & builders would suggest they aren’t interested.

    • Ashir A Gill says:

      Warren I would be very interested in learning about the progress you guys make. If I can help in the group in some form, id be happy to.

  4. Ashir A Gill says:

    Thank you Paul for a very nice article. I am planning on building a home for myself in the country side and started studying the Ontario Building Code out of inquisitiveness. Primary reason we are moving to the is to have no stairs, no basements.
    Am I to understand that in Canada that is not possible or incredibly difficult to build a house without a basement?
    Any solutions, options, choices?

  5. G. Funk says:

    Over the last 40 years Ive been actively volunteering with our faith group building our meeting places 3-4000 sq ft with structural slab on grade with inflow heating system
    Our motive was cost reduction and to the best of my knowledge problem free.
    Built all through Canadas harshest arctic weather zones.
    I am designing a small 2 storey house with slab on grade which will require a engineer review.
    Basements are costly problematic and not recognized as sq footage at real estate marketing.
    I am a structural carpenter contractor with 35 years building custom wood frame homes PWF , Custom Concrete buildings and ICF with some structural steel, love the all but its a building is a costly process and having said that I place a very high level of importance on the structural durability and integrity of constructing anything.

    • Douglas Moffatt says:

      Expect many of us would be interested in the result of your house with slab on grade design effort, including specifics on slab and its insulation along with locale.
      We leased a condo townhouse in Kamloops, B.B. about 18 years ago, 2-story on slab on grade and it was great (although I am not sure of the depth of its edge concrete footings.)

  6. Steve Bator says:

    Slab on grade is an excellent concept because basements are expensive and are a wicking mechanism bringing moisture and water into the house . thousands of dollars can be saved by adding a utility room to the house mudroom or garage. Enough is enough. Make housing affordable by eliminating dated approaches. Start building pragmatic functional floorplans forvthe new millennium.

  7. Abe says:

    Thanks Jay
    We too are interested in the monolithic (thicker perimeter edges) insulated slab on grade home for our retirement/dream home. Are you aware of any municipalities that have accepted this design? We plan to build in the London ON area. I don’t have an issue paying an engineer a couple of hundred bucks to certify, if it saves me tens of thousands in extra concrete and labour. Please keep me posted on any progress or road blocks.

  8. Tamara says:

    I only want slab on grade for my builds

  9. malcolm thomas says:

    I have an Architecturally drawn plan to demolish a detached 16 ft x 22 ft single garage, and on it’s footprint construct an 18ft x 26ft slab on grade 1 B/R (460 sq ft) mini home. The existing damaged concrete floor will be replaced. The proposal is to use a water based in slab radiant heating system as the primary heat source, plus a wall mount A/C unit for cooling. We are currently in consultation with the local Building Inspector whom to-date, has not voiced any concerns with the concept. The build will be in Southern Ontario on the shore of Lake Erie. The heating system contractors we have approached for quotes have also not expressed any warnings regarding the proposal. If we run into objections I certainly will follow up this email with a findings

  10. jeff windover says:

    blind river and alot of other areas in canada allow monolithic slab on grade via using ez forms or eps panels on the exterior and interior of slab to achieve shallow frost free footing

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