The spec matters more on a slab than on almost anything else, because the load is known in advance. A shed pad and a workshop floor with a vehicle lift on it are different pours, and getting the thickness and reinforcement wrong is not something you can correct later.
| What changes | Effect on your price |
|---|---|
| Square footage | The single biggest driver. Work is priced per square foot, so measure before you call. |
| Slab thickness | 4 inches is standard. Going to 5 or 6 inches for heavy vehicles adds material across the whole pour. |
| Reinforcement, wire or fiber | Adds roughly 10 to 15 percent over a plain pour. Worth it anywhere a vehicle or a heavy load will sit. |
| What is going on top | A shed pad, a hot tub base and a workshop floor are different specs. Load and span drive thickness and steel, and those drive the price. |
| Base condition | The wildcard. Sound compacted gravel can lower the price. A failed base that has to be rebuilt raises it more than anything else on this list. |
| Grading and drainage | Priced separately from the concrete. On a sloped or poorly draining site it can be a large share of the job. |
| Vapour barrier and insulation | Needed under anything enclosed or heated. Cheap as a line item, expensive to add later. |
| Concrete truck access | Tight lots, long wheelbarrow runs and pump trucks all add labour to the exact same square footage. |
Call or text with the rough size and what is there now. A photo of the space answers half the questions before anyone drives out.
Someone walks the job, measures it, checks access and drainage, and leaves you a written number. Free, and there is no pressure attached to it.
Once you approve the price the work gets scheduled around the weather window. You get a start date and a realistic finish date, not a vague week.
A slab is specified by what will sit on it. Everything below follows from that one answer.
Four inches is the residential standard for foot traffic, patios and normal vehicles. Anything carrying repeated heavy vehicle loads, a lift, racking or equipment starts thicker and stays thicker across the whole loaded area. It is dramatically cheaper to pour an extra inch now than to discover the slab was undersized after the equipment arrives.
Fiber controls early shrinkage cracking and does nothing structural. Welded wire mesh helps if it is properly chaired at mid depth, and is useless lying on the base. Rebar on a grid is what carries real structural load and is what belongs under anything heavy or over ground that has been disturbed.
The compacted aggregate base is not the place to economise, because it is doing the work of spreading every load the slab receives. Under an enclosed slab, a vapor barrier is equally non negotiable, and its absence limits what can ever be put on the finished floor.
Same principles, very different loads.
Shed and outbuilding slabs, hot tub pads, generator pads, workshop floors and extensions of existing flatwork. The common residential error is pouring four inches everywhere out of habit and then parking something heavy on it. Say what is going on the slab and let the thickness follow.
Commercial slabs are engineered around point loads, racking layouts and forklift traffic, with jointing planned around traffic paths and flatness treated as a specification. They are also normally poured in sections so operations continue, which means construction joints get designed in rather than improvised.
A slab is the most straightforward pour in concrete and the most sensitive to what is underneath it. Almost the entire schedule is preparation, and the concrete itself is one day of it.
Before depth is set, the question is what will sit on it. A slab for garden storage and a slab for a workshop with a lift are different specifications, and the cheapest time to answer that is now.
Topsoil and organics come out. A slab has to bear on compacted subgrade, never on fill that was placed and not compacted, and never on topsoil. This is the step that separates a flat slab in ten years from a cracked one in two.
Compacted stone base placed to the specified depth. It spreads the load and it gives water somewhere to go rather than sitting under the slab.
Anything that will be a floor inside a building gets a vapor barrier under it, lapped and sealed. An open air slab does not need one.
Forms to the finished grade, reinforcement chaired at mid depth, and edges or interior points thickened where a wall, a post or a piece of equipment will concentrate load.
Placed, screeded, floated and finished. Control joints cut the same day, laid out in roughly square panels.
Foot traffic only, kept damp or covered.
Normal loading at about a week, full design strength at 28 days before anything heavy goes on it.
Standard pour rules. The one slab specific risk is rain on an unprotected subgrade before the pour, which turns a ready base into a day of drying and recompacting.
Concrete Slabs across Winston-Salem, Kernersville, Walkertown, Rural Hall, Union Cross, Pfafftown, Clemmons, Lewisville, Stanleyville, Belews Creek, King, Germanton, Oak Ridge, Colfax, Summerfield, Stokesdale, Wallburg, Midway and Welcome.
Most jobs touch more than one of these. If you are already pricing concrete slabs, it is usually worth pricing anything else you have been putting off in the same visit, because the mobilisation is already paid for.
