Payed for a 25X44 building

[muscle]

all concrete will crack. are there contols joins tooled or cut in the concrete slab? there should be a control joint every 10 foot square. this will help control the cracks to hopefully crack within the control joint. on a shop floor i prefer to have the concrete saw cut versus hand tooled like you normally see on sidewalks, etc. this is much nicer when on a creeper or rolling eqipment around as they dont snag on the joint.

I have poured alot of fibermesh concrete and it has performed excellant. make sure you pour at least 3000 PSI with fibermesh and air entrained. start with a 6 slump but be careful adding water as it weakens the mud. if you plan on having large equipment on the slab such as backhoes, tractors, etc the tie in a rebar matt no greater than a 3' on center grid along with using fibermesh. Use a minimum #3 rebar but if you can afford it go with #4. also make sure your subgrade is compacted and do not use an expansive material. i have seen people use a low grade ABC that has alot of clay in it. If moisture is able to migrate under the slab it will cause the subgrade material can expand and heave the concrete.

 

[Fubeca]

desert:

diesel4me:

there is no differance in the foundation requirements for a quonset hut and wood structure. there should absolutely be a complete footing under your building per ibc, and local code. the keyway your inspector describes is required when you pour the footing and later pour the slab on top so that the two "key" into eachother and function as one, deminishing any lateral deflection.

a floating slab is exactly what it is. it is separate from the footings and stemwall foundation. the pics i provided show a floating slab.

Many places allow for a "floating" slab for a detached building - here is an example from a town in Wisconsin. The benefit is less digging and less concrete overall. The footing is integrated into a reinforced concrete slab - but doesn't have to be below the frost line.

(3) FOOTING AND FOUNDATIONS. Attached private garages shall be provided with the same type of footing and foundation as required for the principal building. Concrete floors shall not be less than 4" in thickness. Detached private garages may be built with a continuous floating slab of reinforced concrete not less than 4" in thickness. Reinforcement shall be a minimum of 6" x 6", No. 10 x 10 wire mesh. The slab shall be provided with a thickened edge all around, 8" wide and 8" below top of slab. Exterior wall curbs shall be provided not less than 4" above the finished ground grade adjacent to the garage. Bolts 3/8" in diameter with nuts and washers attached, 6" long, shall be embedded 3" in the concrete curb of detached garages 8' on centers.