# Dig out basement (lower floor)



## Ron6519 (Mar 28, 2007)

That's the way to do it if you have a death wish. I'm imagining you under a pile of house.
You seriously need to call professionals who do this for a living before you do harm.
Ron


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## dhoult (Mar 7, 2009)

Ron6519 said:


> That's the way to do it if you have a death wish. I'm imagining you under a pile of house.
> You seriously need to call professionals who do this for a living before you do harm.
> Ron


While I appreciate your concern for my life, I am trying to become more informed and educated on the subject, so simply telling me to call a professional isn't very helpful.

If you could explain why you think that's a recipe for disaster, I would be very grateful.

Thanks!

Daniel


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## TazinCR (Jun 23, 2008)

What you want can be done. You need to shore the house up on each side of the current footing (with jacks and timbers) and pour the new footing then shift the weight back your new footing when it is cured (30days)
I helped my dad do this very thing 30 years ago. It is a lot of work but you can do it.
Good Luck


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## piecesurpiece (Mar 17, 2009)

wow, just the info I am also looking for. I did glimpse this operation at one stage once, years ago, and am now looking at the same thing for my own building. Also looking for more detail, but pretty much resigned to trying to find a structural engineer to bend the ear of.

As I recall, though, the contractor had sectioned off the whole basement perimeter in 3ft increments with spray paint, labeled 1, 2, 3, 1, 2, 3 etc. When I saw it, he had already dug out and filled in with poured concrete the 1's, and was starting to dig the 2's. The sections seemed to be dug all the way under the wall, and I guess therefore the old footing as well. So I guess you dig out little sections (size determined by engineer) all around the basement at least the width of the previous footers, if not more, and fill them up, before digging the next set of sections. Therefore there are always 3ft dug up, then 6ft solid foundation, and whole thing is done evenly and incrementally. The floor had not been touched at the time I saw the work. I imagine all the central floor digging is done after the foundation is completely shored up.

The basement I saw was a 1920's 2 storey in Toronto, and it now has full height, and is dry, with no 'bench' around the basement perimeter that I can recall.

So it seems that you have part of the answer, but the idea seems to be not to go excavate then underpin adjacent sections one by one around the foundation, but rather to have multiple stages of spread out small excavated then underpinned sections, perhaps done more in the order of a star pattern...

Feedback?


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## caritimo (Mar 25, 2009)

I've been researching this for a while as well - if you want to have a quick demo, check out the video on HGTV.ca's Sarah's House, Season I:
http://www.hgtv.ca/sarahshouse/video.aspx?releasePID=RydxNTbcqGviL28Wxw9qGReDbYk5UOYS
From what I've seen already, you need to dig out portions of the foundation one by one, consolidate with concrete and then proceed to a new portion, gradually completing the basement perimeter. I think only after that is done do you then dig out the main floor and re-concrete entire surface of the basement.
I concur with Ron6519 - this is a very delicate job and I'm considering it myself for my house here in Montreal, but would NEVER attempt it on my own: playing around with the foundation of your home? Not without a full-blown warranty from a company that knows what it is doing!


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## Wildie (Jul 23, 2008)

My daughters house had the basement excavated in this manner. 
Looking at the signs from the forming, it appears that they under mined the footings in a 5 foot section, formed it up and poured the concrete! Then the skipped 5 feet and excavated another 5 foot section. Formed and poured again! They went around the whole perimeter under-pinning in the same manner.
I assume that once the under-pinning was complete, the excavation was completed and the missing sections finished!


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## Knucklez (Oct 21, 2007)

you might try search term "excavation" 

i'm thinking of similar project. but i will ask structural engineer his/her advice before i start project. also will get permit for this job too (mostly as 2nd opinion on critical reno). 

remember that you loose headroom when you finish the floor & ceiling.. so you need more like 3' lower to have 8' ceiling.

please post your project & what you learn along the way!

Knucklez


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## Scuba_Dave (Jan 16, 2009)

dhoult said:


> If you could explain why you think that's a recipe for disaster, I would be very grateful.
> Thanks!
> Daniel
> 
> Dig to the level of the bottom of the existing footing.


This part could be a recipe for disaster
Digging all the way around to the bottom of the footoing would be a mistake I think. If there is any outside pressure the walls could fall. I would do one section at a time

You most likely will have a ledge all the way around
The footer will stikc ina few inches past the walls:


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## Knucklez (Oct 21, 2007)

scuba.. in your picture, on the top of the wall is a piece of wood flat against the top with anchor bolts. why is there no gasket? 

is it right to have direct wood/concrete contact?

Knucklez


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## Scuba_Dave (Jan 16, 2009)

Not my pic, just some diagram I found
PT can be in direct contact with concrete
I use foam underneath the PT


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## jomama45 (Nov 13, 2008)

Just for the record, adding basement depth is probably the most expensive & labor intensive square footage you can possibly add to a house. I would personally look into a first floor addition with a full basement or moving somewhere else. JMO


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## wildcat (Oct 24, 2008)

I would not recommend messing with your basement. I would advise you to build up or out. Much better finished product and lighter on your pocket book. 

Just for giggles though, what type of basement/foundation walls do you have? Also, where is grade in reference to the top of the basement wall or in reference to the finished first floor?


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## dhoult (Mar 7, 2009)

wildcat said:


> I would not recommend messing with your basement. I would advise you to build up or out. Much better finished product and lighter on your pocket book.
> 
> Just for giggles though, what type of basement/foundation walls do you have? Also, where is grade in reference to the top of the basement wall or in reference to the finished first floor?



I have concrete block walls, and grade is about 4.5 feet above the slab, and 1.5 feet below the first floor/top of basement wall.


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## dhoult (Mar 7, 2009)

jomama45 said:


> Just for the record, adding basement depth is probably the most expensive & labor intensive square footage you can possibly add to a house. I would personally look into a first floor addition with a full basement or moving somewhere else. JMO




Actually, I have already gone up and out. I just finished adding a second story by myself, as well as a small addition off the back, so I'm certainly capable of doing a lot of the work myself to save money... now I want to go down


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## dhoult (Mar 7, 2009)

Knucklez said:


> you might try search term "excavation"


well that's a smart idea... haha. I'll do that 



> i'm thinking of similar project. but i will ask structural engineer his/her advice before i start project. also will get permit for this job too (mostly as 2nd opinion on critical reno).


I've actually spoken with a structural engineer and foundation expert, and they wouldn't tell me anything specific about how to do it. 





> remember that you loose headroom when you finish the floor & ceiling.. so you need more like 3' lower to have 8' ceiling.
> 
> please post your project & what you learn along the way!
> 
> Knucklez



I actually had a blog up about building the second story on my house (complete with an insanely long narrative and lots of pictures of the progress). If anyone's interested, I can try to get it up again and post a link.


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## dhoult (Mar 7, 2009)

caritimo said:


> I've been researching this for a while as well - if you want to have a quick demo, check out the video on HGTV.ca's Sarah's House, Season I:
> http://www.hgtv.ca/sarahshouse/video.aspx?releasePID=RydxNTbcqGviL28Wxw9qGReDbYk5UOYS
> From what I've seen already, you need to dig out portions of the foundation one by one, consolidate with concrete and then proceed to a new portion, gradually completing the basement perimeter. I think only after that is done do you then dig out the main floor and re-concrete entire surface of the basement.


I tried to watch the video, but it wouldn't let me since I'm not in Canada!! Is it worth it for me to find a proxy server in Canada to watch it?



> I concur with Ron6519 - this is a very delicate job and I'm considering it myself for my house here in Montreal, but would NEVER attempt it on my own: playing around with the foundation of your home? Not without a full-blown warranty from a company that knows what it is doing!



You're probably right, and I haven't decided whether I actually want to do this on my own yet... one of the reasons I'm trying to get more info. I still haven't heard anyone say anything about attaching the new foundation/footing, or if it's even necessary.

One other thing I was thinking about... It seems to me that I wouldn't be able to guarantee I completely filled the void with concrete after digging under the footing, and therefore some settling would occur. What about not quite filling it all the way, and then packing the space with something? Anyone have any comments/suggestions?


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## Scuba_Dave (Jan 16, 2009)

dhoult said:


> I've actually spoken with a structural engineer and foundation expert, and they wouldn't tell me anything specific about how to do it.


So you hired an engineer to help you & they wouldn't?

Or you were just looking for free advice ?? :whistling2:


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## dhoult (Mar 7, 2009)

Scuba_Dave said:


> So you hired an engineer to help you & they wouldn't?
> 
> Or you were just looking for free advice ?? :whistling2:



Well I hired a structural engineer a while back to make sure my foundation could support the second story I built, but he didn't seem to be able to tell me anything more specific than what I've already said when I asked him about lowering the floor.

I also spoke with a foundation person about hiring him to draw me some plans for doing the work, but he said he wouldn't do it if I was potentially going to do the work myself. (And I don't need to hear from anyone that I should take that as a sign.... )


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## Scuba_Dave (Jan 16, 2009)

That is a sign
Most likely no-one will be responsible for telling you how to do this due to the risk involved with collapse


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## joel v. (Jan 26, 2009)

First off let me say that am not going to be responsible for what I write in the reply or any other reply on this forum. If I was that desperate for extra space I would probably do that to a basement but you should be aware that even if that basement doesn't leak water now it could when you dig another 3 feet down. You also have to be EXTREMELY CAREFUL when you go and possibly undermind the main structure of you house.
What I would do is dig a hole about 4 feet deep and 1 foot wide every 4 feet. I would then pour a footing about 2x2x1 foot deep. Do that all around you house and wait 30 days for it too cure. Then get some 6x6 pt post and cut them to fit between the new footing and the old footing. When you place them in be sure toplace it under the old wall and not just under the footing. You can now proceed to dig the rest down 3-4 feet. Make another footing in the area of 12"x6" deep. Pour a new wall directly under the old wall. It will have to come out past the footing to be able to get the concrete into the forms.( if you wall is 6"wide and the footing is 12"wide then you will have to go under the wall plus another 3 inches to come flush with the footing then another 3 inches to be able to get the concrete in there) Let that cure but in the mean time you can clean out the rest of the basement and pour a new slab. Again do not consider this good conprehensive advice. I would recommend building an addition as far as living comfort and cost go.


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## dhoult (Mar 7, 2009)

Scuba_Dave said:


> That is a sign
> Most likely no-one will be responsible for telling you how to do this due to the risk involved with collapse


Obviously I can't blame anyone for advice given to me here. I think there's even a disclaimer to that effect somewhere. But I do understand that no one wants to hear about a house collapse in Maryland after posting here, let alone with a body underneath.


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## GeDeBel (Dec 30, 2009)

*Hi Caritimo*



caritimo said:


> I've been researching this for a while as well - if you want to have a quick demo, check out the video on HGTV.ca's Sarah's House, Season I:
> http://www.hgtv.ca/sarahshouse/video.aspx?releasePID=RydxNTbcqGviL28Wxw9qGReDbYk5UOYS
> From what I've seen already, you need to dig out portions of the foundation one by one, consolidate with concrete and then proceed to a new portion, gradually completing the basement perimeter. I think only after that is done do you then dig out the main floor and re-concrete entire surface of the basement.
> I concur with Ron6519 - this is a very delicate job and I'm considering it myself for my house here in Montreal, but would NEVER attempt it on my own: playing around with the foundation of your home? Not without a full-blown warranty from a company that knows what it is doing!


Hi Caritimo,

Have you done the work of digging the basement of your house in Montreal? I am looking into doing the same, can you give me any reference for the contractor...Thanks a lot


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## caritimo (Mar 25, 2009)

*Basement digs in Montreal*

The plan is to do it summer 2010. I have started contacting contractors:
Henault & Gosselin
Bisson Experts
They came, but haven't provided quotes yet. They are considered the full service and expensive options. Their solution is a big job of digging underneath existing foundation either to reach bedrock or to place wide metal plates on top of which to pour concrete. Either method would obviously be done in sections.

I have also contacted an independent engineer who claims with his solution he could be half the price of the other two. His solution is to place jacks every 2m that would support house while digging the rest (it's more detailed than that, but I didn't quite understand it).

I am still mulling about what to do and I think I will continue searching for a few more options.

Good luck to you. Are you also in Montreal?


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## SPS-1 (Oct 21, 2008)

dhoult said:


> If you could explain why you think that's a recipe for disaster, I would be very grateful.
> 
> 
> Daniel


Its not clear what happened here, but appears to be something you should review:

http://www.contractortalk.com/f11/house-collapse-70196/

Steve


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## GeDeBel (Dec 30, 2009)

*HI Caritimo*

HI, I in South Shore. Thanks for your reference. I am planning to start mine around end of February before spring....but have not decided which contractor. THanks for you reply


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## badsanta (Apr 19, 2011)

I know this is old, But how did it go?


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## sparkewe (Jun 20, 2011)

*Resource*

I've been thinking about this as well with my basement...found an AWESOME forum that had pictures start to finish. 

http://www.avsforum.com/avs-vb/showthread.php?t=1235793

Hope that helps!


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## Knucklez (Oct 21, 2007)

ya, i saw that post also and thought it was good. i have done a lot of research on this subject now and have a good feeling on the process involved. there is not a lot of info out there, you REALLY have to search. i have not found a single book on residential underpinging. another good website is http://www.contractortalk.com

i saw a another blog where it rained and then the holes for the underping were filled with water. that would FREAK ME OUT if i were in the process of underpinning and it got all soggy and wet. but the blog i was reading said that they called the structural engineer and he said it was no problem, but you can wet shop vac the water out so you can keep working. 

i am still trying to learn how to deal with a chimney. looks like you underpin half of it, and then the other half. 

also, how to deal with the sewage & water lines that are currently UNDER the foudation wall but will actually be in the area between the new footing and original foundation wall after underpinning process. are these pipes supposed to be surrounted with plastic ABS to create an air gap until the cement dries... and then fill with foam? remove ABS and fill with foam? none of the above? don't know yet.

this project is a long way away for me, so i got some time. post your pics if you already started!

Knucklez


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