Concrete slab for shed

[brians]

I am planning to build a 12x16 shed this summer, and have decided to go with a concrete slab for the floor instead of plywood. I plan on preparing the site myself, as far as getting a stone base in and setting the forms, and then having someone come in to pour the concrete.
I plan on laying down a 4" base of 3/4" blue stone, and then a 4" slab, with threaded anchors set in around the perimeter to secure the framing.
Will that be sufficient for a shed? I live in Maryland.
Thanks,
Brian

[Rich]

Should be perfect. Make sure not to get too far away from the corners for your anchor bolts. It would be a good idea to thicken the edge slab also.

[brians]

Thanks for the reply Rich. How thick should the edges be? I was thinking I could set 2x6s for the forms, plan to have the whole thing be 4", but extend it down to 5.5 inches around the edges. Does that make any sense? I guess I should talk to the guy doing the pour!
Brian

[Rich]

I think for something that size you would be ok with 5.5 to 8 inches at edges.

[mjpliv]

A grid of 15mm rebar @16" OC both ways would go a long way to holding this slab together if you ever have a settling or erosion problem later on. Using just a welded wire mesh will hold the slab together but will not prevent it from deforming/cracking.

[mjpliv]

Will there ever be vehicle loads on this floor?

[RobBase]

Good advice from these guys Brian. Definitely make sure you put down the gravel base especially if you live on clay soils.

Also buy a small roll of wire mesh from Home Depot and make sure they finisher pulls it up in the middle of the slab as he pours it.

Lastly, as soon as he finishes troweling or brooming the slab, mist it with water and cover it with poly sheeting for 3 days or so.

[brians]

Do I need to be concerned about frost heave? What is the norm when planning a shed built on a slab?
RobBase: I see you live in Maryland, I'm in Queen Anne's County.

Brian

[Rich]

Frost heave is always a concern. Typically with a shed it's not a concern.. but then again that will depend on if you are concerned with a little movement under it.
Frost will be much worse if vehicles or traffic is around the shed. Essentially the weight of vehicles push the frost down farther and farther. If you don't have much traffic around it I wouldn't be concerned too much - but it's still no guarantee that it won't heave up a little now and then.
If you are concerned with heaving I would look into a shallow frost free foundation. The NAHB has done quite an extensive white paper on this type of foundation and have had excellent results. Essentially it places insulation along the side of the foundation and then out away from the foundation creating a barrier against the frost from being pushed under the structure. I bought the paper a number of years back - I'll see if I can dig it up and find some more particulars.