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I will be building a 24’x37′ story-and-a-half garage into a hillside. The back wall will be 9′ from top of slab to grade. Obviously the front is at grade and the side walls are partially exposed.
This is southern Wisonsin so I’ll be using frost footings at the front. However, since the back and side walls will have to designed as a cantilevered retaining walls I’d like to minimize the wall height. Any guidance on the need for frost footings at the back wall and side walls?
Thanks!
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LC:
If I understand your layout correctly, your objective is to minimize your concrete wall heights on top of spread footings. If the back wall is 9 ft. tall because grade is so high then there is no need for the top of the spread footing to be any further down than the bottom of the slab. In other words, the slab's perimeter at the back wall should rests on the top edge of the spread ftg..
I visualize that the side walls have grade starting at 9 ft. and sloping down to the grade at the front to roughly the slab elevation, rather than anything like terracing happen'g. If so, then you could (startring at the front wall frost footing) "trench" the footing to the same depth as you turn the corner; and, continue this trench footing along the side until you get to a point where the expected "finish grade" is atleast as high as the required "frost line" distance. > From that point on, you can start the spread footing at the level I described at the start.
Hope I envisioned this correctly for you. Let me know otherwise. Happy Planning!
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I will be building a 24'x37' story-and-a-half garage into a hillside. The back wall will be 9' from top of slab to grade. Obviously the front is at grade and the side walls are partially exposed.
This is southern Wisonsin so I'll be using frost footings at the front. However, since the back and side walls will have to designed as a cantilevered retaining walls I'd like to minimize the wall height. Any guidance on the need for frost footings at the back wall and side walls?
Thanks!
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LC,
If you have 9' of hillside against the back wall, be careful to account for the pressure that much earth will exert on that wall. Sounds like you already have that in mind. I built one 40' wide in a hillside and had only 6' of earth against the back wall. The homeowner was concerned about water along that wall. Did my best to create a swail in back, but because of the slope it was tough to form, so I back filled with gravel, and ran the footer drain to daylight. That was 6years ago and he's had no problems.