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Discussion Starter · #1 ·
I am bidding on site work for a future (next year) garage.
Floating concrete slab.
location is northern minnesota, deep freeze land.
The location is on the side of a hill, the back side of the garage will be five feet into the orginal elevation of the hill.
I am planning to bid the following work.
40 x 56 garage slab area
excavate area is to be 60 x 66
excavate into slope of hill zero cut infront and three feet in back.
the excess hill behind garage will be excavated to divert water around garage.
install french drain behind garage to channel water into drain tile that will also be installed on the side excavated walls of the excavated area to flow out the front of the garage area.
natural soil is all clay.
cut into clay soil resulting in a level bottom, with back cut three feet into hill, after removing 2 feet above that (3 feet) for drainage away from building.
excess clay soil behind garage above three feet deep cut will be removed for drainage.
will use pit run gravel compacted to make a three foot thick base for slab.
this is deep freeze land.
Any suggestions or comments on my plan, will take a lot of time involved here to build a base on this unique site.

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Joking aside, he probably could excavate down to the frost line and fill with crushed stone and pour a slab on top of this. The question is, is it more economical to excavate out the whole building or just the perimeter? Obviously the latter is more economical and that is why it is done that way.

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Are you doing site work or whole job? Sounds like an excavation question. Assuming these are plans approved by building department.....I am not familiar with N MN but I am guessing frost line is about 8 feet or so. But it would be crazy to go down 8'+ just for a slab, you would just do a basement at that point. It may be that floating slabs are acceptable there, esp. with detached garages. I have to assume so since you are looking at the plans. I would say that site conditions and local building codes are going to be more helpful in dictating which way you go, but that clay......ouch. Good luck
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