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Worth lowering basement while insulating?

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  • Jan 3rd, 2023 11:45 am
[OP]
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Oct 16, 2022
6 posts
1 upvote

Worth lowering basement while insulating?

Doing a big green reno of our 100-year-old Toronto house. The basement is finished, with 6'4" ceilings, but has no insulation either in the walls or below the slab. We are replacing the HVAC essentially entirely, and insulating the walls, of course, as well as doing interior waterproofing. We plan to open up the slab to insulate below as well. The floorplate is 500 square feet.

We don't plan on using the basement extensively, so hadn't planned on underpinning or otherwise lowering the basement. But given that we are going to crack the slab anyway, what is the ballpark additional cost of dropping the floor six inches to a foot through benching? Obviously many variables, but are we talking 5k, 20k, 50k, or what? Thanks!
13 replies
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Jan 6, 2002
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No. (imho.)
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Oct 13, 2008
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RFDKB1 wrote: We don't plan on using the basement extensively, so hadn't planned on underpinning or otherwise lowering the basement. But given that we are going to crack the slab anyway, what is the ballpark additional cost of dropping the floor six inches to a foot through benching? Obviously many variables, but are we talking 5k, 20k, 50k, or what? Thanks!
No .... not worth it.
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Jul 5, 2004
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$50k wouldn't be out of the question
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Sep 5, 2009
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$50k seems about right. Turn it into an apartment. That’s what we did when renovating. We had no intention of using the basement and contractors told us we were nuts not to rent.

2 years later and the rental income has paid $40,000 of a $100,000 basement renovation.
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Oct 2, 2018
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'Worth it' is a relative term, if you're very well off then sure sky's the limit, for those just getting by then likely not.

However $50k is ballpark so you can decide what is within your means and wants.

Personally making the space fully useable is worth the cost to me, it's the financial cost that many have concerns with.
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[OP]
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Oct 16, 2022
6 posts
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Just to clarify, I am asking the additional cost of lowering a foot or so given that we are already cracking the slab to insulate below and to replace plumbing/HVAC/etc., not the total cost of this project.

Definitely not planning to rent, which would require a much more detailed basement reno (and we have no interest in having tenants in our own house, particularly given the nigh impossibility of evicting a bad one in Toronto).
Deal Guru
Jan 25, 2007
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Paris
RFDKB1 wrote: Just to clarify, I am asking the additional cost of lowering a foot or so given that we are already cracking the slab to insulate below and to replace plumbing/HVAC/etc., not the total cost of this project.

Definitely not planning to rent, which would require a much more detailed basement reno (and we have no interest in having tenants in our own house, particularly given the nigh impossibility of evicting a bad one in Toronto).
The additional costs are $50k, which as someone who just had a foundation poured with easy access seems low to me. My guess is around $80k. You are talking about HAND digging under your existing footings to add another foot of footing and wall. All the pining in place to make sure your house doesnt fall down will be an immense effort, plus taking all of the waste out of the basement by hand, and adding concrete back in.

My friend just finished digging a trench all the way around the inside of his outside wall of his basement and he removed close to 8 tonnes of waste, and carried 8 tonnes backs down to refill it, all up and down a ladder (stairs had to be removed).
[OP]
Newbie
Oct 16, 2022
6 posts
1 upvote
Jerico wrote: The additional costs are $50k, which as someone who just had a foundation poured with easy access seems low to me. My guess is around $80k. You are talking about HAND digging under your existing footings to add another foot of footing and wall. All the pining in place to make sure your house doesnt fall down will be an immense effort, plus taking all of the waste out of the basement by hand, and adding concrete back in.

My friend just finished digging a trench all the way around the inside of his outside wall of his basement and he removed close to 8 tonnes of waste, and carried 8 tonnes backs down to refill it, all up and down a ladder (stairs had to be removed).
Got it, thanks. We actually have an existing walk-out (crazy for the ceiling height, I know) and the house is square rather than narrow and long, so benching down a foot to make an 18x18 room rather than underpinning would be an option (and hence nothing is being dug under the existing footings).
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Jan 25, 2007
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Paris
RFDKB1 wrote: Got it, thanks. We actually have an existing walk-out (crazy for the ceiling height, I know) and the house is square rather than narrow and long, so benching down a foot to make an 18x18 room rather than underpinning would be an option (and hence nothing is being dug under the existing footings).
How would you achieve this? You would still need to add a foot of footings, and the walkout makes it worse. My shop is also a walk out, and the footings at the walkout end are about 3.5 feet below the floor. To lower my floor a foot, we would need to dig down that 3 feet and add another foot. Your footings still would need to be 3 feet plus under your new floor height.
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Sr. Member
Mar 25, 2002
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50k would be on the lower end, keep in mind the soft costs as well (Architect/Permits)

Again all depends on the size etc being underpinned, I have a few quotes from some of the more reputable under pinning companies in Toronto and it will be 80k+ including a separate entrance for my basement.
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Mar 13, 2004
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your just over 6ft on your ceilings right now in the basement. Ours is similar height finished and its fine for us.
I would leave it how it is and use the money to properly water proof from the OUTSIDE and not the Inside. You want to stop the water from coming inside the house not deal with it after its inside which could be doing damage you cannot see.
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Dec 4, 2009
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RFDKB1 wrote: We don't plan on using the basement extensively, so hadn't planned on underpinning or otherwise lowering the basement. But given that we are going to crack the slab anyway, what is the ballpark additional cost of dropping the floor six inches to a foot through benching? Obviously many variables, but are we talking 5k, 20k, 50k, or what? Thanks!
I think "cracking the slab" is the easy part of what you're thinking of doing. Seeing as you don't plan on using the basement extensively, I wouldn't bother.

I've often found, once you start doing a,b,c it quickly and unexpectedly leads to x,y,z. Especially in a 100yr old home.
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Lucky
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Mar 22, 2017
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Personally I'd ask around as having an entire additional floor turn from storage into usable space would be important to me. It's a lot cheaper than an addition. If you have a walkout, then you can also finish and rent out the space for quite good money, meaning it gets paid back (excluding the increase in equity from having a usable basement). It's also worth nothing that a basement rarely gets used if it's 6'4", but might be used a lot more if it's 8'+ and nice to be in.

So yeah I'd do it because it'll be partially offset by equity increase, more than fully offset by renting it as a unit, and if you decide to use it yourself someday then you now have a lot of extra space which can be in somewhat short supply in many older Toronto homes.

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