Lowering A Basement: When Does It Make Sense?


We’ve had several homeowners contact us in recent months, with the idea of lowering the basement floor in their house to create more liveable space in the basement.  As always, they ask us if it is a project that makes financial sense.

First, let’s start with a definition.  Lowering a basement floor, or underpinning, is a process of digging below the existing basement footings and walls which support the house, and extending the walls downwards.  The work is done in small sections, since the house would collapse if it was all done at the same time.  And since it is being done from the inside of the home, it relies primarily on manual labour to complete the work.

Lowering a basement floor to create additional living space has become a popular project in Toronto, especially in older two and three storey home on small lots, which do not have space to go up or out.

So back to the question, when does this project make sense?  We’ll use three projects we looked at recently as examples.

House #1 – The homeowner lives in a 2 storey home, approximately 2,000 square feet in size.  The plan is to lower the basement floor to create additional living space in the basement, while the main floor and second floor of the house will remain untouched.

House #2 – The homeowner lives in a small two bedroom bungalow, on a small lot.  She wants to add a second floor, completely renovate the main floor, and lower the basement floor.

House #3 – The homeowner lives in a bungalow on a large lot in Etobicoke, and has plans to add an addition at the back of the house, renovate the existing house, and lower the basement floor.

So what did we think of these projects?

Lowering the basement floor in House #1 makes sense.  The work is confined to the basement area, and no other renovations are being contemplated.  Lowering the basement is a cost effective way to add valuable living space to the home.

The proposed renovation of house #3, combining an addition, renovation and basement lowering is an expensive project.  It would be less costly to tear down the old house and build a brand new home.  We would not recommend basement lowering as a cost effective option in this case.

House #2 is also an expensive project, which would generally be more effectively approached by tearing down and rebuilding.  However the small lot is an important factor to consider.  The existing house may be larger than currently permitted in zoning bylaws, and a new house may have to be smaller if it was torn down and rebuilt.  Keeping the existing house avoids potential issues with zoning.

A similar situation to the small lot issue is a semi-detached house, which is attached the neighbouring home and can’t be torn down.  In this case, lowering the basement is a good option to consider.

Read more about whether it makes sense to build an addition vs tear down and build a new home here.