Pad thickness

[2nrguy]

Thinking of adding a garage/man cave to the property around the spring time and was wondering if anyone in the area could offer some advice.

I'm about 45min south of Chicago. So i get the full temp swing going on. As far as i can tell from digging post holes for a fence in the past, there is about 3-5in of black dirt on top of a minimum 4FT of clay.

I know I want at least a 2 post lift in the garage if not a 4post. From the reading I've been doing on here, it seems like i need at least a 6in thick pad(for the anchors to be secured into). I would like to have the entire pad poured the same depth so I wont have to worry about placement of the lift.

Thought i would check what the thoughts were here first before going to deal with the idiots in zoning.

 

[sublimate]

You should really check with the manufacturer of the particular lift you want to install.

Bendpak answers that here:
http://www.bendpak.com/support/frequently-asked-questions/

XPR-10
10,000-lb. Capacity
4" Min. Thickness / 3,000 psi

XPR-12C
12,000-lb. Capacity / Clearfloor / Triple-Telescope Arms
6" Min. Thickness / 3,000 psi

XPR-15C
15,000-lb. Capacity / Clearfloor / Standard Arms
6" Min. Thickness / 3,000 psi

XPR-18C
18,000-lb. Capacity / Clearfloor / Standard Arms
8" Min. Thickness / 3,000 psi

 

[2nrguy]

See, didnt even think of that. Thanks.

 

[p_mori7]

My soil conditions were similar to yours, and I also have to deal with freeze/thaw cycle.

I excavated all the sod and then another 12" of soil.

Then I laid down 12" of compacted 0-3/4" gravel (also known as crush & run I think).

Then laid the forms snapped a chalk line all around to get 12" edge thickness to my slab.

Then filled in the center with 6-7" of compacted gravel. Then rebar and wire mesh.

The slab is still perfectly flat & level. A few hairline cracks now, but that's it.

I am happy with the outcome.

 

[wssix99]

Be sure to add an inch for variability across the slab and maybe more if you are going to do an insulated slab.

 

[404]

My soil conditions were similar to yours, and I also have to deal with freeze/thaw cycle.

I excavated all the sod and then another 12" of soil.

Then I laid down 12" of compacted 0-3/4" gravel (also known as crush & run I think).

Then laid the forms snapped a chalk line all around to get 12" edge thickness to my slab.

Then filled in the center with 6-7" of compacted gravel. Then rebar and wire mesh.

The slab is still perfectly flat & level. A few hairline cracks now, but that's it.

I am happy with the outcome.

Crusher run, what comes out of the crusher before any sieving or sorting.

 

[Falcon67]

Your local permit/building dept should have minimum recommendations on foundation requirements for garages and exterior buildings. Get the docs, know what the inspector knows. Actually, know it better. Makes the conversation much easier.

 

[Cyberbear]

While thickness is always an important consideration, I see few comments about quality.
The amount of cement in concrete is also a critical factor since strength requires it. I always use what if often called a 7 bag mix, which is an industry term where I live.
The freeze and thaw cycle needs to be considered in those types of locations, and that is where the strength is important as well as weight support.