What Is Basement Underpinning?

As a contracting group specializing in basement underpinning in Toronto, we often get asked this simple question, “what is underpinning?”  Below is a brief answer to that question.

“Underpinning” is an industry term that’s generally used to describe reinforcing an existing foundation. This may be to shore-up a structure that was poorly built originally or has degraded over time, is subject to subsidence or land-slippage, or is being prepared to carry extra weight.  Underpinning is also performed when a homeowner wants to have their basement foundation dug out to increase the ceiling height of their basement.  This is also known as basement lowering.

Digging out a Toronto home for underpinning

.What’s That Got to Do with Basements?

Contractors usually become involved with underpinning basement walls because a home owner decides to deepen them to create a full height basement. In this instance, they are sometimes originally little more than crawlspace below a floor. At other times, the plan may be to deepen a basement built for storage, so as to create living space with livable head-height.

Simply excavating out the floor could upset the balance of the foundations, as they slide inwards and crack the walls above. That’s why it’s necessary to dig under them to create a new foundation. Basement underpinning solves the problem of “which comes first, the chicken or the egg?”

Stages in the Process

If there was a single basement job not recommended for amateurs or the uninsured), then basement underpinning has to be the one. Get it right, and you’ll add significant value to your home. Get it wrong though, and you could end up damaging the fabric of your house.

Appoint a licensed structural engineer with a record of completed jobs, to prepare statutory documents and obtain approval for the job.

Appoint a basement-underpinning contractor who’s similarly experienced to complete the following work:

Toronto home underpinning


  • Remove a small section of the existing foundation to obtain access underground, and replace it with a load-bearing joist.


  • Excavate alternate strips to the required depth, and pour shuttered reinforced concrete beneath the exposed sections of foundation.


  • When the new foundations are completely cured, complete the balance of the basement underpinning.


  • Lay a new floor when everything is stable, and build out the interior of the extended space.

Cost-Benefit Analysis

Houses are valued in terms of living space. A new basement could therefore increase the value of your home by up to 10% – and you get more living space too. Basements are especially popular when it comes to extending homes, because they retain existing footprints, and seldom affect the neighbors.

However, you are effectively building your house “upside down” by adding the walls and floor when the roof’s up already. While the job’s in process the structural integrity of the entire building is compromised in the short-run. If it fails, then your new basement could end up costing you a whole lot more than it’s worth.

adding a finished basement in toronto

Insure Yourself

Of course, you should take out extra insurance while the work’s in progress. But no insurer will compensate you for loss caused by an incompetent builder you chose yourself. It’s highly recommended to find an experienced basement under-pinner who is licensed (and insured themselves).


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NuSite Group is a Toronto based basement waterproofing and foundation repair company that specializes in Basement Waterproofing, Basement Lowering, and Foundation Repairs. Call us today at 416-622-7000 or 905-731-1228 for a free in-home estimate and inspection.

4 Responses to What Is Basement Underpinning?

  1. I like your tip on how a basement could increase the value of your home by up to 10%. It seems that if you successfully underpin your home you could really end up making your home worth more. My wife and I have been considering underpinning our home so maybe we should consider the increase of value our home could have if we do it.

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Mark Lipton - Homestars Review

Basement Waterproofing

Our basement leaked! Of course . . . we bought a 100 year old house! But my office needed to be in the basement permanently. I interviewed 10 different companies until we decided on the Steinbergs and their crew at Nu-Site! They are professional, reliable, courteous, honest, and they really make an effort to communicate with the client about every step of the process.

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After several years of chronic leaks, we decided to have our basement waterproofed once and for all. The team over at Nusite was professional, answered my questions during the project and stayed within their quoted price....which is always a concern for me when working with contractors. Great job overall

Joshua Persaud - Yellowpages Review

Basement Waterproofing

Had several cracks in my basement wall and they would leak whenever we had a heavy rain. It started about a year and a half ago and seems to have gotten worse over the past 6 months. I tried having my neighbor seal it, but it started leaking again within a few weeks. Called several waterproofing companies and got several quotes. Finally went with Nusite contractors for the job. They gave a reasonable quote and I liked the guy that came by for the estimate. They stayed within budget and cleaned up before they left. It's been almost 3 months now and it seems to be working great.