# Foundation underpinning



## Leafan

Hey guys. I have a client that wants their basement floor lowered a good 12-18 inches. This is something I don't have alot of exp with. (no worries I am getting quotes as well) 

So what's the best way to do this. ?? I know there are a few methods.

The attached picture is what I am planing on doing. I figure we will dig down to the existing footings. Then start working 4' sections lowering and adding the footing extension. 

Any tips or advice from you guys is always appreciated


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## TheBuildingFirm

Rent a conveyor.


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## jomama

Constructing the wall in a manner similar to the picture is guaranteed to leak for sure.

Generally, underpinning is by far the most expensive square footage you can add to a house. But the site is probably too small for an addition?


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## Leafan

jomama said:


> Constructing the wall in a manner similar to the picture is guaranteed to leak for sure.
> 
> Generally, underpinning is by far the most expensive square footage you can add to a house. But the site is probably too small for an addition?


The site is decent sized. And we are adding a second floor. Will total close to 3000sqft when done. But the bsmt is 7'3 high and he wants push it to 8'.


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## Leafan

TheBuildingFirm said:


> Rent a conveyor.


Lol definitely


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## jomama

I think every homeowner with a basement under 8' wants "just a few more inches". The reason you won't find much info on the web on how it's done is because it's rarely done due to the cost and it's highly job specific.

The picture has a ton of issues. The joint between the existing footing and wall will constantly leak, unless it's in an arid climate. The existing concrete floor is just part of the system that's required to keep the base of the wall from rotating inward. W/O the floor there, you'll need some serious dowel work between the footing & wall. I wouldn't even bother trying to conjur up a guess as to cost to complete the job w/o first getting an onsite inspection & drawn plan from a structural engineer.


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## TheBuildingFirm

Jomama, it's actually quite common to underpin older homes in this neck of the woods. You are correct that there will be some water migration between the existing footing and the new bench footing. All of the underpinning I have done, we had to add dimple drain floor to ceiling along with a interior weeper. 

Is it an acceptable method....for sure. Is it cost effective? That's for the clients to decide.


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## MikeV

In Toronto you have to limit the underpinning to 3' lengths, separate by 6' undisturbed. If the foundation wall is crumbling, or the soil is sandy, you may have to limit to 18" section. We always put a layer of Delta MS or something like it from the interior weepers up to grade to control any water that may come in at the old footing level. You need a permit, and maybe a structural design as well. Since this is an expensive job, you should also push the client to put in radiant heating, which can be connected to the water heater. That depends on how large the floor is. There is a specific way to do the plumbing so that you don't get stale water in the pipes over the summer, and all of the parts have to be for potable water, including an all bronze circulating pump. Count on $150 per running foot of underpinning only, and then you have the excavation of the floor, the interior waterproofing and the new floor. You can also do some bench footing which costs about $100 per foot. We have done the benches in conjunction with underpinning. If you have a 1' bench, you can build shelving above the bench, or something like that. You will probably need a sump pump and pit, and also a sewage ejector pump. You should count on $1,200 each, installed and connected.


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## PPRI

Why not just lift the house and add it to the top of the foundation?


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## Leafan

PPRI said:


> Why not just lift the house and add it to the top of the foundation?


Is that really feasible. Were talking about a 1400 sqft home here Double brick...... How would one go about lifting an entire house??? I guess it's possible. But ........


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## PPRI

New basement underpins were the bread and butter when I was a sapling. My grandpa was an oldschool mason and his house mover lifted some houses you would never believe would hold together well enough to lift. Those same lifters grandsons just lifted a two story that had been added onto 3 times for me this last season. It involves a lot of beams a lot of angle iron and a lot of yelling. A good lifter/mover could lift it no problem.


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## Rockmonster

Lifting, and in some cases moving houses in big business here. We have tons of houses that were built pre Civil War, and often the new owners decide that the weak link was/is the foundation. So they go from 18" or so to 10' or so. And a company from the Midwest was here maybe a year ago, and moved a _massive_ brick lighthouse about a quarter mile. This is a great option if a) you have a company nearby that does this, and b) the owners have some money, as it is not cheap......It is very doable......


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## Leafan

Rockmonster said:


> Lifting, and in some cases moving houses in big business here. We have tons of houses that were built pre Civil War, and often the new owners decide that the weak link was/is the foundation. So they go from 18" or so to 10' or so. And a company from the Midwest was here maybe a year ago, and moved a massive brick lighthouse about a quarter mile. This is a great option if a) you have a company nearby that does this, and b) the owners have some money, as it is not cheap......It is very doable......


I think the only problem with the whole lifting idea is we are already trying to push the Hight restrictions on living space. We are 6" higher than the allowed Hight. We are submitting the plans anyways. I see a few houses in the area are as high as we are hoping for. So I don't anticipate any problems. But to further lift the house 8" I think will not go over well. 

Besides it sounds like it's probably in tge same ballpark pricewise as underpinning


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## S.R.E.

Leafan said:


> I think the only problem with the whole lifting idea is we are already trying to push the Hight restrictions on living space. We are 6" higher than the allowed Hight. We are submitting the plans anyways. I see a few houses in the area are as high as we are hoping for. So I don't anticipate any problems. But to further lift the house 8" I think will not go over well.
> 
> Besides it sounds like it's probably in tge same ballpark pricewise as underpinning


Then lift the house, support it, and remove the existing foundation and install a deeper one. that way you might be able to lose the 6" you are over height. Just make sure the client has wads of Cash before you start. :thumbsup:


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## dcbuilder

*Underpinning*

We have to underpin in almost every project we do here in DC. Houses here almost never have full height height basements, and when we convert a rowhome to condos, the basement needs to be underpinned to get enough headroom. I have some engineer's specs I could send you from our last project if you're interested. Want them?


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## Leafan

dcbuilder said:


> We have to underpin in almost every project we do here in DC. Houses here almost never have full height height basements, and when we convert a rowhome to condos, the basement needs to be underpinned to get enough headroom. I have some engineer's specs I could send you from our last project if you're interested. Want them?


That would be awesome. Thanks. I have been swamped like crazy the last month and change. I haven't even scheduled the time to do this underpinning thing. Lol.


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## HallisseyDesign

IF you don't want to spend the money underpinning that wall you can also pour the dead wall and that will shore it up and cost a lot less and then you can talk them into going like 8'6 to give you a little more work for saving them all the other money.


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## designbuildnj

*Under Pinning Foundation*

Based on the picture and the scope of work I think you summed it up pretty good in the last paragraph of your post. I really think this is the way to go as well as the cheapest.:thumbup:


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## Redneckpete

Here's what your underpin pours look like.


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