Underpinning

Blockade

I would agree, the top of the footing is at the height of the doors threshold. The footing is extended 18" down to the bottom of the excavation. This puts the footing at 18" below grade, as the doors threshold is at grade. The footing will be challenged by frost if frost penetrates deeper than 18” in this part of the country.

LNG24

This might help: The new cement pour is the new footing. The bottom of that pour is 46" below finished grade. See pic

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Blockade

LNG...Good visuals, verses the written word. Seeing a picture and reading someone’s explanation sometimes has conflicting messages. I was judging the height of the footing based on the form work, material, hammer and casting left in the green concrete and trench walls. This does not reflect the reality of what you have done. I do see now by your drawing that the bottom of the footing is 42 inches below grade, and if that is deep enough in your area to resist frost, then my hat is off to you for a job well done. This process is not done enough to create good space from a basement room. You can even take the excavation out further so that a patio can be presented.

LNG24

Thanks Blockade. I try to tell all contractors building new homes to include Walk Out basements, but very few want to be bothered.

Did you see the finished pictures? The narrowest point is over 6' wide and where you see the t-111, that will eventually have a door to a new room under the current addition on the house. That will be an interesting dig!

The deck is HUGS so no need for a big patio here, just need access to the massive deck. FYI: deck is the same square footage as the house and we are making it bigger!

Next year will will have to support the current addition which they (previous owners) never excavated out under before building. There are NO footings under it! It was built on an old deck. I'll be putting some Micro Lams sistered up to the existing floor (deck) joists so I can span the entire length without support in the middle. Then we will get a steel beam under the outside edge, remove all the posts and dig it out. That will result in an additional 216 sq ft. added to the house. My Future Work Shop!

LNG24

I finished this a while ago, but never posted the final pics. OK, I still need to cap the block and steps in the Spring. After two years of having a mud pit and dreaming of my walk out...here it is

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LNG24

and more pics

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ruskent

So larry your mortared the retaining wall block together?

LNG24

Interesting, isn't it? Was not my idea, but the masons who put up the wall. These were left over from a job and I could not beat the price, if it holds. But I have their guarantee that it will.

Its kind of like a SRW block, but there are no grooves to lock them in and I wanted a vertical wall. So we used mortar between and filled the blocks and voids behind the blocks, the V's with cement too. There is also rebar vertical every other hole and horizontal every other course.

Not shown in the pics is, 2' of gravel behind the wall from the footing up to the second to last block. This winter was the wet (we had some heavy rain before the snow, and coldest at 2 degrees (only 10 today) and I am not seeing any signs of movement. Knocking on wood and keeping my fingers crossed.

neolitic

It's tedious, but deadmen
let you breath easier.
Cable ties from the vertical
re-bar back to helical anchors
in the undisturbed soil.
Try it next time.

By cable ties, I meant tie-backs
made with cable, not those
plastic things.....

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Tom M

I was curious about that wall too. Im not being critical I think the job came out great, I dont do walls like that. The rebar was the smart thing for sure. I was looking for some drain holes, did you get some in there?

LNG24

No Drain Holes! I did not want water pouring out onto the slab. Instead I used a 2' wide gravel back fill with 2 4" drains at the bottom to collect the water. I maintained the 2' thickness by using plywood to fill in the gravel on one side and dirt on the other. Then we would pull it up and fill in more. Water flows from those drains non stop and did not freeze up this winter.

Boadey

how do you have the floor drain tied in?

PrecisionCandR

wow.. i learned ALOT from this posts... im so glad i found this site

job well done!

greg24k

Nice work LNG, I know it was some job, did something like this a few years back.

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LNG24

Not exactly what you mean by tied in. I have a 4" Perf Pipe under that slab in a gravel trench taking the water to a sump pump pit. Same pit that the footing drain for the wall ties into.

The pit is temporary and permanent. Temporary as in the pump that is in there will eventually be removed once the excavation is completed under that addition. At that point, the pipe will be continued to daylight and the sump pump pit will revert to being a manhole of sorts where multiple drain lines tie in and exit via a 6" solid PVC to daylight. The pit will be used as a clean out as well. The pit is located right in front of the T-111 between the wall and the existing foundation.

We have had a bad winter in regards to cold and freeze thaw cycles. Wall is doing good (and I am knocking on wood ) I personally do not like block walls let alone like this. I always did poured and if I was doing this for a customer and not myself, I would have only done a poured wall.

BuiltByMAC

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

Boadey

Thanks, that does answer my question.. I have a similar set up at my home. Whats the worry on the block? Expansive soil? With that 2’ of gravel behind it, you should be fine.

Come on mac, that takes all the fun out.

Redneckpete

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).

You are correct that the heat bleeding from the basement may keep the frost out from under the back half of the old footing. That also would have been the case WITHOUT any concrete poured under the front, and the concrete you poured may actually have protected the front of your footing while making the back half more vulnerable.

Let me explain how.

The concrete you poured does not go to the back of the existing footing. The frost can penetrate sideways (yes frost will penetrate in every direction) through the new concrete you poured and into the dirt under the backside of the footing. The only thing preventing this is the heat loss from the building.

That creates a problem for you. Poured concrete has a r-value of .08 per inch, or essentially nothing. Concrete should not count as insulating value for frost protection. Earth has a r-value of .25 - .4 per inch. Thus, the dirt on the back of your footing is 3-5 times MORE exposed to the cold then it was before you poured any concrete.

Bleeding heat from a building to keep frost away is bad building practice. At the very least it creates a cold spot on the floor in front of the door, and could actually cause sweating of the concrete floor as well. Should the frost make it though, (perhaps you turn down the heat for an extended vacation and it's really cold outside) you could have issues with the door sticking.

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

rbsremodeling

The concrete underpinning is as wide or wider than the original footing. There is no void as you described.

Have you ever done an underpinning job?

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Redneckpete

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 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