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Foundation Wall Beside Existing Slab

 
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Old 10-18-2018, 11:26 PM   #1
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Foundation Wall Beside Existing Slab


Hey Guy,

I have a garage addition coming up where I need to remove a part of a exposed aggregate patio to add a tandem bay to a garage.

The existing attached garage has 4ft poured concrete walls with the pad poured inside of it

My question is is there any way to pour the new walls tight to a saw cut on the patio so that when I’m finished there isn’t a section of patio missing beside the garage wall?

(If this is in the wrong section feel free to move it)
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Old 10-19-2018, 02:10 AM   #2
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Re: Foundation Wall Beside Existing Slab


Layout the "footing edges" on the patio concrete, wet saw full depth, make a second cut 8-12" further in, save the pieces, reinstall on block 'brick'ledge, caulk the new joint, using stainless pin keep the saw cuts level with the un-cut patio SOG...

dig and pour the new footing fast!. use non shrink back fill....bid in at least ONE do over when it settles.

Under promise, everything but COST.

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Old 10-19-2018, 03:49 PM   #3
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Re: Foundation Wall Beside Existing Slab


You would have to do a "Blind Side" foundation.

Essentially, you need to form the inside wall and soil is the outside form. We use bentonite sheet to waterproof the foundation.

The biggest hassle is making sure the form bracing for the inside wall is stout enough hold fast without tie backs to the outside form.

So in short, yes it can be done.
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Old 10-20-2018, 08:12 AM   #4
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Re: Foundation Wall Beside Existing Slab


How deep and wide do you need to go?

Along what tgeb is talking about the blind side footing. Could you do a “shovel” footing.
Just dig the proper depth and width, pour it full with concrete letting the soil be your “forms”. Then form the walls and pour them as normal on top of it.
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Old 10-20-2018, 08:53 AM   #5
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Re: Foundation Wall Beside Existing Slab


Thanks guys that’s what I was hopping to hear. I knew it was possible but getting confirmation that I’m not losing my mind is great.

The footing needs to be 4ft down to get below the frost line. The existing wall is 8inches thick so I would match that to make it uniform.
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Old 10-20-2018, 12:44 PM   #6
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Re: Foundation Wall Beside Existing Slab


By far easier, would be cutting away the SOG above the toe of the footing and replacing it with other material as transition/border, like brick/CMU pavers or new crete with an colored mix?.

Or using the demoed washed finished old crete cut up as large 'paving stones' laid in sand. like the first post less the caulk and pins, and the pieces sawed into common lengths...

As a practical matter, you can't easily stand on the last 4" of slab that abuts a sided garage wall anyway....

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