Toronto Semi - digging basement lower

myleviApril 5, 2010

The current ceiling height is 6'5 where there are no furnace ducts. I would be happy with only one more foot. The basement is about 400 square feet. There is a common party wall with the attached neighbour. Any idea of what this would cost for a professional to do it? Can I do it myself? Do I need a permit? Where can I find the information necessary for me to do this job? The house is at Coxwell and Gerrard. It's brick construction about 1960's I think.

I appreciate any help or comments.

Cheers!

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worthy

Check with the Buildings Department for current rules. Dial 311.

I did this at Bathurst/ Dupont (about 750 sq. ft.) in the late '80s working from the stamped plan of a structural engineer.

You can do the work in one of two ways: remove all soil in three-foot sections and underpin or dig down about two feet in from the wall and build a "bench" around the existing wall. Much will depend on the soil. Coxwell and Gerard may be very sandy, so the bench method may not be feasible.

Because of the structural nature of the work, this is not a diy job. I would look for a company that specializes in this work.

I didn't intend to lower the basement floor. But when I removed the finished surfaces put in by the previous owner, I found that he had done so with no attention to what he was doing. There was a dirt floor, the footings were undermined and the exterior brick wall was starting to show settlement cracks. You would have thought I was on crack to have bought this fixer upper to begin with!! But hot real estate markets make people do strange things.

    Bookmark   April 5, 2010 at 1:46PM
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mylevi

I understand the Hot Real Estate market thing for sure. We were in a bidding war and had to remove all conditions for the offer to be accepted. I don't even care about making the basement legal for a second suite, I just want to be able to use it comfortably myself. A 2 foot bench around the perimeter doesn't leave much floor space. Somewhere I read that if you only lower by a foot, that it won't undermine the original footings so a bench may not be necessary.

    Bookmark   April 5, 2010 at 2:23PM
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A newer home such as yours will typically have 4"-5" of gravel followed by an equal thickness of concrete. Remove that and you're below the level of the footings, thus undermining the material they're sitting on.

If you make a mistake, you may be paying your neighbour's repairs too.

    Bookmark   April 5, 2010 at 3:54PM
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mylevi

Is there any other method of lowering the basement floor without losing so much square footage?

Thanks for your comments by the way. They are very much appreciated!

    Bookmark   April 7, 2010 at 1:15AM
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brickeyee

"Is there any other method of lowering the basement floor without losing so much square footage?"

Digging under the foundation in sections and shoring.

    Bookmark   April 7, 2010 at 11:16AM
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mylevi

Is that what underpinning is?

    Bookmark   April 7, 2010 at 12:56PM
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Same thing.

Underpinning to increase headroom in a basement.
Image: Draincom.com

This is not an endorsement.

    Bookmark   April 7, 2010 at 2:17PM
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The image above reminds me of the surgical illustrations in medical books my physician father used to show me in his attempt to have me follow in his footsteps. He always admonished me that when you start cutting, it doesn't look much like the illustrations: blood starts flowing, greasy fat gets in the way of your scalpel and the organs aren't always where they're supposed to be. At that point, I would blanch and grow faint, knowing my future wasn't in medicine.

    Bookmark   April 7, 2010 at 2:26PM
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mylevi

LMAO

Well this picture does suggest that this process is indeed a lot of work. Do you have to dig on the outside of the wall as well as the inside?

    Bookmark   April 8, 2010 at 9:15AM
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Do you have to dig on the outside of the wall as well as the inside?

Typically not.

But once you start digging, you have to be prepared for anything.

I dropped by a large detached late 19th Century house under renovation on Rusholme south of Bloor. In the gutted basement where people were working I noticed a dark wavy line about six feet up. It was a high water mark, left when water had rushed into the basement as the floor was being excavated for greater headroom. They had no choice then but to install two large pumps with backup power running continuously.

Looking at the map below, it looks like they had hit one of the tributaries of Garrison Creek, one of Toronto's many hidden rivers.

Source: Lost Rivers of Toronto

There may have been a reason beyond saving a row of blocks that the original builder of your home went with a 6.5 foot basement height.



Here is a link that might be useful: Lost Rivers of Toronto

    Bookmark   April 8, 2010 at 10:13AM
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