Concrete slabs for sheds, garages and workshops in Warner Robins, GA

Slab prices by what is going on top

Shed and carport rows are square footage times $6 to $9. The garage row works out to about $7.30 to $11.30 per square foot because the footings take a second day, the slab is an inch thicker and the pour is inspected; the workshop row is the garage rate scaled by area. The driveway cost guide explains why small pours cost more per foot. Removing an old slab first is $2 to $4 per square foot.

Shed and carport slabs: 4 inches with a thickened edge

A shed slab does not fail in the middle; it fails at the edge, where the wall load sits on scraped clay. So the perimeter is where the concrete goes.

• Slab: 4 inches of 4,000 psi concrete, 6x6 wire mesh or fiber, over 4 inches of compacted crusher run.
• Edge: turned down 12 inches deep and 8 to 12 inches wide all round, with a continuous #4 bar. The wall sits on that, not on the 4-inch field.
• Height: the slab finishes 4 inches above grade, 6 if the shed has wood siding, so splash stays off the wall.
• Anchors: for a metal carport kit we set the manufacturer's bolts in the wet concrete from their drawing. A shed company drills wedge anchors later.

Permits: many Georgia jurisdictions exempt accessory buildings under 200 square feet, but setbacks still apply and rules differ inside and outside city limits. Ask Houston County Building Inspection, 200 Carl Vinson Parkway, Warner Robins, GA 31088, (478) 542-2018, or your city, before you order the shed. We will not pour in a setback.

Garage and workshop slabs: footings, bolts and a vapor barrier

1. Plan first. We need the building drawing before we dig: door openings, column lines, the floor drain and the conduit stubs. All of it goes in before concrete.
2. Excavation. The field comes down 9 to 10 inches. Monolithic footings are trenched 12 inches wide and at least 12 inches below finished grade around the perimeter and under any interior bearing line.
3. Base, barrier and steel. 4 inches of compacted stone, 6 mil polyethylene over the whole field so clay moisture does not wick into the floor, two continuous #4 bars in the footing, and #3 rebar on 24-inch centers at mid-depth. A two-car garage gets 5 inches; a workshop with a vehicle lift or a tractor gets 6.
4. Inspection. Houston County Building Inspection or the city looks at footings, steel and bolts before we call the truck. Plan a day for it.
5. Pour. Ready-mix comes from plants on Foy Evans Drive and Plantation Road in Warner Robins and Industrial Park Drive in Perry, so trucks reach most Houston County addresses in under 30 minutes. A garage floor slopes 1/8 inch per foot to the door; a workshop floor is flat with a drain. Half-inch anchor bolts go in wet at 6 feet on center and within 12 inches of each corner, or to the plan. Saw-cut joints at 10 to 12 feet, on the column grid.
6. Cure. In summer we pour early, mist the surface, and apply a white-pigmented curing compound. You can walk on it next day, park a car after 7 days, and it reaches design strength at 28 days. Framing can start after 7 days; keep the forklift delivering the building off it until 28.

Red clay, water and where the slab sits

Houston County sits where the Fall Line sandhills meet the red clay of the upper Coastal Plain. The clay swells when wet and shrinks when dry, and that movement, not traffic, is what cracks most slabs here. A slab with a building on it cannot be re-leveled the way a patio can, so the grading around it matters as much as what is under it. We set the finished floor above the surrounding ground, cut a swale on the uphill side where the lot falls toward the building, and push you to put gutters on anything bigger than a shed, because the drip line from a 24-foot roof lands straight on the footing. On red clay south of Russell Parkway and out toward Feagin Mill Road, expect most of day one to go on digging out soft spots, and the price in the upper half of the range.

When you do not need a slab

• Small resin or metal sheds. Under about 8 by 10 feet, 4 inches of compacted gravel in a treated frame does the job for less than our $1,200 minimum. A slab makes sense when you want a floor to sweep, a building anchored against wind, or anything over 120 square feet.
• A hot tub on an existing patio. A full 8 by 8 tub with four people loads the slab at under 100 pounds per square foot. A sound 4-inch patio on compacted base carries it; one on soft fill does not.
• A sunken slab under a shed that still stands. Foam leveling at $600 to $2,500 lifts it without touching the building.
• A workshop you have not designed yet. Moving a floor drain after the pour costs more than the slab did. Decide the building, its doors and its utilities first.