# Underpinning



## LNG24

BuiltByMAC said:


> Hey LNG, Excellent thread! I learned a lot about something I knew nothing about!
> 
> One thought comes to mind looking at the ground level deck next to the 5' drop off - maybe a handrail system on that side of the deck so folks don't take a tumble into the newly excavated well?
> 
> Mac


Actually Mac, there is a bench seat that goes in that spot along the entire length of the wall. Its not in place yet because I need to modify it to fit the new dimensions which are smaller than the original dimensions. I'll be adding a back to the bench as well because well, I have good parties :thumbup:



Redneckpete said:


> Sorry guys, I've been busy and haven't been on this forum for a while.
> 
> I'm not trying to be contrary, or critical, and your end product looks great, good for you!
> 
> That said, I would never get away with constructing the walkout that way here (Southern Ontario)....
> ...Not the end of the world, but also not necessary. Ideally the concrete would have been under the entire footing, and insulated from the living space. Code here calls for r-12 on any basement wall to four feet below grade. 2 1/2 inches of SM insulation would have fit the bill nicely.
> 
> I'm really not trying to bash your workmanship or imply you are facing a catastrophic problem because you are likely not. Lets all learn from each other.
> 
> Pete


Hey Pete, What I built was EXACTLY how you would have built it if you were building from scratch. The ONLY exception is that it was not a continous pour and there is a horizontal seam where the old footing and new footing meet. Oh, and my new footing is wider than the original footing. There is no void because the new concrete was poured above the bottom of the old and vibrated in place. I will stand behind that design against any engineer. Now the wall we did :whistling I have my fingers crossed there. 

Take a look at this drawing, maybe that will help you understand it better


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## rbsremodeling

Redneckpete said:


> Foolish man you are. You have no idea who you are talking too, and the first stupid comment you make is questioning if I have ever done an underpin. You may be a big fish here, I don't know. Nevertheless, you are mistaken on every front.
> 
> Perhaps you were expecting me to tell you that I have never done any underpinning, that I was an inexperienced contractor who liked to lurk on forums such as this, simply to criticize and bring down the contractors I si clearly hate.
> 
> Regardless of your stupidity, I will respond.
> 
> Check out the post on this time and date. "10-09-2008, 01:04 AM " He posts a sketch SHOWING the underpin as I described it. I certainly must be incorrect in expecting that he constructed the underpin the same way as he drew it.
> 
> Pete


Have you ever done underpinning before? 

Where is the void being left? 

Do you see a void in his pictures of the actual pour?

I ask if you have done an underpin before because the questions you asked made me assume you didn't or have not done it correctly. 

This is a great thread, with great illustrations and pictures. The pictures showed that his pour is as wide or wider than the existing footing, what did I miss?


and its Mr. Stupidity:thumbsup:


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## Redneckpete

LNG24 said:


> What we ended up doing was to dig back (by hand ) approximately 1/2 the width of the footing (to the inside of the wall its supporting) so that left a portion of the footing on existing soil. See drawing.
> 
> Here are the pics. Will keep you posted.


Guys, I seriously couldn't care less, but from what was posted in the past it seems clear the dirt was left under the back of the footing. Knock yourselves out, do it like that every time, but it ain't done right. That dirt could freeze and will heave it it does so. Your house, not mine.

Pete


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## rbsremodeling

Redneckpete said:


> Guys, I seriously couldn't care less, but from what was posted in the past it seems clear the dirt was left under the back of the footing. Knock yourselves out, do it like that every time, but it ain't done right. That dirt could freeze and will heave it it does so. Your house, not mine.
> 
> Pete


Pete 

The back of the footing (the Side of the footing that is facing the inside of the house)? I am confused now


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## Redneckpete

Here are the problems as I see them with LNG's install, notated on LNG's sketch.










Here is how it could have been done better.










Feel free to disagree and debate coherently with me. I enjoy sharing and receiving advice, not trading pathetic barbs such as "you've never done this before and if you have you've done it wrong."

Pete


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## LNG24

Its true what they say, A picture is worth a thousand words.

Pete, Yes this is exactly how it was done. I must agree with you that the SM would be a great addition in a perfect world and if it was built prior to the completion of the house. In fact, in this area...Southern NY, we only just started putting an insulation barrier on the foundations, but it is installed on the exterior of the concrete prior to back filling. 

I think there is a large void between BEST practices and Acceptable Practices. Today we seal up ever nook and cranny with spray foam. A Best Practice, but it far exceeds Acceptable. Of course that in its self caused a host of other problems requiring Air Exchangers and Radon Mitigation Systems.

Every foundation in this area for a single family 1 or 2 story home built prior to 1990 is done on a 12" x 24-32" footing and a block or poured concrete wall 8" thick with 42" of that wall being underground. 

Using your theory, every interior slab around here should be heaving as the frost can easily get through the 8" concrete wall. To date, I have never seen that happen. If I am building a new home, do with insulate the below grade portion of a foundation...YES. Do we do it the way you drew...ONLY on COMMERCIAL. Is it a BEST Practice...YES. Is it the ONLY way...NO, Is it required where you are??? I have no idea, but its not here. 

Can you step out a footing like I did? According to our engineer...YES


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## Driftwood

*Question for LNG on Area drain*

I see an area drain. Does it drain to daylight By gravity? ,where does it dump?
Sump pit and pumped Up? Thanks' Drift


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## LNG24

Sounds like you are planning on something similar. Put up some pics for us to look at. Here is the drain plan. Right now there is an automatic sump pump that pumps into my leader drain which runs to daylight. 

The red line is a future drain to daylight using gravity and not the pump, but we can not put that in until the excavation of dirt under that portion of the house and a foundation is added under there. 

So what do you have going on?

(FYI: the footing drain behind the wall will eventually run around the outside of the new foundation of the addition. At that point the line going under the concrete will be disconnected and filled with concrete. It too will run to daylight.)


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## Driftwood

*Thank You LNG*

I do a lot of this work. I also do all My plumbing. Our larger retaining walls
are all Eng. Geo Tecks. are great teachers. I just have an interest in this work.
Thanks again Drift


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## jmacd

*We did one too*

I am new to this site, here is my firts post. This is a photo of a school we are working on that had underpinning involved, a lot of hand work. Did the work in 4' sections. 
View attachment 20900

Demo of the footing was not fun.


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## Stock

Thank lads enjoyed this thread,have done some underpinning years ago but at least we don't have the issues you have with frost penetration we might get three consecutive days of frost here over the winter ,last winter we had a week of frost in January keep up the good work and the brilliant posts .


Stock


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## ch0mpie

jmacd said:


> I am new to this site, here is my firts post. This is a photo of a school we are working on that had underpinning involved, a lot of hand work. Did the work in 4' sections.
> View attachment 20900
> 
> Demo of the footing was not fun.


 your engineer saw that photo?


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## jmacd

What's your point? Project is engineered. Project was done to plans. You know more than the very well paid company that put this project together?


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## neolitic

Your "pillar" seems a bit...
skimpy?


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## jmacd

Possible, but the dimension were spelled out on the plans that’s how we built it. The footing is wider than 16" we undermined; footing was 60", 12" thick poured wall that could have something to do with it. Notice the paint marks on the wall, this is a very large footing built 1965. Anyways the project is done and no settlement. The excavation was much larger area than photo shows when we were done. We also had to cut a door in the wall, used a hydro diamond chain unit to do the cut. The chain was $1000 bucks then we had to pull the very large concrete block out of the hole with new footing in place, wish I had a photo of that. All this for an elevator. I don't design em' just build em.


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## ch0mpie

Seems like you have a lot of unsupported building all at one time. Maybe I don't exactly understand what you are trying to do. You poured concrete in those two open areas under the building after excavating? Maybe you could explain your methodology a little better.


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## jmacd

Yes, we then formed up the two areas and poured them along with some footings. Then the space between the new and the old was dry packed with non shrink grout and then the other areas were dug out, formed and poured, then dry packed also. It looks like a larger area than it was, the footing had quite a bit still supported even in the dug out area because the footing was so wide. The excavated area was 4’, I guess we could of dug only one at a time but I wasn’t going to offer that being that it would of cost me more to do because of travel times etc.


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## ch0mpie

so that pillar supporting the building shown in the picture is a previously poured underpinning pier or soil?


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## jmacd

Undisturbed soil, gravel mix. Are you thinking that the building should of shifted? Are thinking the specs were wrong? What two sections would you take out first, maybe the ends and then the corner? I don't make it a habit to question the plans unless I know for a fact it won't work or two dangerous


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## neolitic

.....and I ain't afraid of nuthin.:blink:


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