A 12x12 slab covers 144 square feet, and two jobs call for this size over and over: a base for a mid-size shed, and a hot tub pad. Same square footage, very different slabs, and the difference is worth pricing on purpose.
Example math at 144 square feet
| Finish | Example rate | 12x12 (144 sq ft) |
|---|---|---|
| Standard broom | $9 / sq ft | $1,296 |
| Exposed aggregate | $13 / sq ft | $1,872 |
Example rates only, not market prices. A shed base gets broom finish and nobody ever looks at it again. A hot tub pad sits in the middle of someone’s backyard, which is where a finish upgrade like exposed aggregate starts coming up in the conversation.
A hot tub pad is not a shed base
A filled hot tub plus the people in it is a serious load parked on a small footprint, and it never moves to give the slab a break. Where 4 inches is the normal call for a shed, many contractors pour hot tub pads thicker and reinforce them. At the example add-on rate of $1.50 per square foot, mesh on this pad is $216, which is a cheap line item next to a cracked slab under someone’s tub.
The pad also has to be dead level. A tub shell is not made to sit on a slope, so the forming and screeding get more careful as the slab gets smaller, not less.
Small pour, full-size fixed costs
At 4 inches, 144 square feet is only about 1.8 yards of concrete (144 x 1/3 ft, divided by 27). The crew, the forms, and the trip cost the same as they would on a far bigger pour. If $1,296 at the example broom rate sits below your floor, quote your floor instead, and pricing small jobs so they pay covers how to do that without losing the work.
Add-ons move this number fast too. Tearing out an old pad at the example $4 per square foot adds $576, and site prep at the example $2 adds another $288.
Run any other size
The concrete slab cost calculator opens preloaded with this size. Change the length and width for anything else, and read how to price a concrete slab for the full method behind the rates.
When the numbers are yours instead of examples, this quote takes about ten seconds on your phone. That is what the PriceDesk free trial is for.