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Discussion Starter · #1 ·
I'm a professional but not in the concrete business. I do need some advice please. I have a 24x24 garage that I need to put a 32 to 36 inch frost wall on one side asap. The garage slab is floating with no footing at 4 inch thick. Im unsure if the slab can hold 4 course of block or a poured wall? The exterior will be backfill with 24 to 28 inches of soil. It is in northern wi so I do have snow load. I'm not looking for a easy way but the right way that will last. Any advice would be great. Thanks
 

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I'm confused. A frost wall goes below the slab, a retaining wall goes above the slab. Sounds like you need a retaining wall. Any chance you have enough room to fit a retaining wall behind the garage, and independent of the garage slab all together?
 

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You can dig under or cut it out and dig that way. Depends on whats above the section, garage doors only? Make sure it is properly braced if needed. Could do 4' sections skipping 8 feet then 4' sections.
 

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I understand but how deep should I go with the footing? I live in northern wi. I already build a temp wall to support the roof so I can do it all at once. And do I connect the slab to wall with like rebar where they meet?
 

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What does you're code in the area say footings need to be for depth? Check with city.

Never rebar slab to wall! Smooth steel dowels, expansion joint and grease (or plastic) sleeve the dowel in the pad.
 

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Take a deep breath..... Floating slab and then converting One wall to frost footing????? Guaranteed to fail. If you need to pile dirt against one side of the pre-existing slab on grade, build the retaining wall separate from the legacy floating garage. Drain tile,washed rock back fill, filter cloth, etc... Some type of mira-drain system over a Bituthan(WR Grace)type of water proofing over the existing stud wall. N Wisconsin = 48" frost footing?

A giant "window well" out of purpose made retaining wall concrete dry laid block or a trenched and form poured in place concrete retaining wall with adequate rebar.

If you insist on building a bi-sexual footing, just dig and pour/lay a new footing toward the problem, and make the garage that much larger, cutting off the bottom of the moved wall to fit on the higher sill. Infill the side walls and extend(add a truss) the roof.
If the roof trusses bear on the relocated wall some lintels and posts would be required to carry the old roof structure.
 
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Woody,

Be smart and act professional, call an Engineer. That is the best thing you can do for yourself and your customer in this situation.
There is so many factors which must be considered when designing that wall and internet is not the place for that.

Good luck
 

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Imagine two garages side by side, one Slab on Grade, the other Frost footinged... tied together, every wet or dry period and every time the dirt under the SOG froze, you'd have IRRESISTABLE differential movement that would require a sliding control joint between the two modes of footings. If you left the roof bearing only on the SOG, the new portion walls would have to have a few inches of room a the top plate pocket steel track to restrain it on the X and Y Axises, and Quality control joints the changeover points between the walls on either system, Electrical wires, plumbing. air lines etc would have to have special consideration wherever they crossed the Control joints....
Structually 2 buildings rubbing together...

If the garage was heated, you could insulate the old SOG part adjacient horizontally around the perimeter as they do in Canada, but without a constant heat source, the garage door will loose to much for that to stop frost occourring under the slab, and you'd still have 48" of soil volume changes as moisture levels change during the year.
 
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