How to Bid a Concrete Slab Job

The short answer

Bid concrete slabs in four parts: yardage (length × width × thickness in feet, ÷ 27, plus 5–10% overage), forming ($2–$4/sq ft), base and reinforcement ($1–$3/sq ft), and finishing ($2–$4/sq ft). All-in, residential flatwork lands at $6–$12 per sq ft in most US markets in 2026 — if your number is under $6, you forgot something. Then adjust for access, demo, grade, and weather before the number ever reaches the client.

Concrete is the least forgiving trade to underbid. There's no undo button on a pour — a bad bid doesn't just cost margin, it can cost the entire job in a tear-out. Every section below exists because someone learned it the expensive way.

Full bid breakdown

Step 1: Get the yardage right

The formula: (length × width × thickness in feet) ÷ 27. Worked examples for the jobs you'll bid most:

Always order 5–10% over the math. Subgrade is never perfectly flat, forms flex, and coming up short mid-pour is the most expensive mistake in concrete — a second short-load fee plus a cold joint you'll see forever. Most suppliers have a 1–3 yard minimum and charge short-load fees under ~5 yards, so small jobs carry disproportionate delivery cost. Price that in.

Run it in the concrete calculator to double-check — it handles waste factor and bag-vs-truck math.

Step 2: Price the whole job, not just the mud

Beginners bid the concrete and donate everything else. The mud is typically only a third to half of a flatwork bid. Walk through each line:

• Forming ($2–$4/sq ft): straight runs are fast; curves, steps, and thickened edges are slow. Price steps per step ($75–$150 each), not per foot.
• Base ($1–$2/sq ft): 4 inches of compacted gravel. If the soil is soft clay or fill, you need more — and the excavation to make room for it.
• Reinforcement: #4 rebar on 18-inch centers, chaired up into the middle of the slab, for driveways. Welded wire mesh works for patios only if it ends up in the concrete — mesh left lying on the subgrade does literally nothing. Fiber mesh in the mix controls shrinkage cracking during cure.
• Finishing ($2–$4/sq ft): broom finish is the residential standard (slip-resistant). Hard-trowel is for interiors. Stamped/decorative adds $3–$8/sq ft — it's a specialty bid, not an add-on.

Step 3: Walk the site — then adjust

• Access: can the mixer get within chute reach (~15 ft)? If not, it's wheelbarrow crews (slow, +$500+) or a pump truck ($500–$1,000). Backyard patios behind a house with no side access are pump jobs — bid it.
• Grade: sloped sites need taller forms, more gravel, and more mud than the flat math says. A 6-inch fall across the slab adds real yardage.
• Demo ($2–$4/sq ft): breaking, loading, and hauling old concrete. Always a separate line — clients accept it when they see it; they resent it when it's “included” and the total looks high.
• Weather: above 90°F, you need retarders, extra crew, and possibly a morning pour — concrete that sets too fast can't be finished properly. Below 40°F, heated enclosures and insulated blankets. Both cost money; both go on the bid.
• Drainage: where does water go now, and where will it go after you pave? A slab that ponds water against the foundation is a callback and a liability. Slope 1/4 inch per foot away from structures, minimum.

Step 4: Specify the mix like a pro

The bid should name the mix, not just “concrete.” For exterior residential work in 2026, the standard spec is 4,000 PSI, air-entrained, 3/4-inch aggregate. Air entrainment (tiny bubbles in the mix) is what lets exterior concrete survive freeze-thaw — in northern markets it's non-negotiable, and skipping it to save $10/yard is how slabs spall in three years. Slump: 4 inches for flatwork. If the driver wants to add water to make it flow easier, that's your strength pouring out — every gallon over the design drops PSI and increases cracking.

Pro tips from the trade

• Cut joints the same day. Control joints go in 6–12 hours after finishing (or saw-cut the next morning at the latest). Joints cut late are decoration — the concrete already decided where to crack.
• Never burn a slab you'll broom. Over-troweling exterior concrete seals the surface and traps bleed water — it scales off in the first winter. Broom it and walk away.
• Cure it, don't just finish it. Concrete gains strength for 28 days. Curing compound or 7 days of wet burlap/plastic in heat makes measurably stronger concrete. It costs almost nothing and almost nobody bids it — put it on the quote and explain it.
• Sell the sealer. Penetrating sealer at $0.75–$1.50/sq ft protects against de-icers and oil stains with great margin. Offer it on every exterior job; take-rate is high when you explain freeze-thaw.
• Photograph the base. Gravel depth, compaction, rebar chairs — shoot it all before the pour. When a client asks why your bid beat the cheap guy's by $800, the photos answer.

Costly mistakes to avoid

• Under-ordering mud. Covered above — the 5–10% overage is the cheapest insurance in construction.
• Bidding demo as “included.” Break it out. A $2,400 slab with a $900 demo line beats a $3,300 lump sum every time in the client's mind.
• Forgetting the pump. Discovering on pour day that the truck can't reach means a panicked pump booking at premium rates — or wheelbarrowing 8 yards. Check access at the estimate.
• Water in the mix. Tell the crew: no added water without your okay. A soupy mix finishes easy and fails early.
• Vague scope. State thickness, PSI, air entrainment, finish type, joint spacing, and exclusions (demo, permits, pump-if-needed, sealer optional). The written scope is the only thing between you and a free re-pour.

Mix designs by application

Don't bid “concrete” — bid the mix. The PSI, thickness, and reinforcement change with the job, and so does the price:

Air entrainment for anything exterior in freeze country, 3/4-inch aggregate for flatwork, 4-inch slump. When a supplier quotes you, confirm all four — “4,000 PSI air-entrained” means nothing without the slump and aggregate the price assumed.

Decorative concrete: a separate trade on the bid

Stamped, exposed-aggregate, and stained concrete run $8–$18/sq ft installed — roughly double plain flatwork — and they bid differently: pattern/color selection up front, release agents and coloring priced per job (not per foot), and sealing as a required final step, not an upsell. Don't fold decorative work into a flatwork bid as a line item; quote it as its own scope with its own samples. Clients choosing decorative are buying looks — show them cured samples in daylight, not brochure photos, and get the pattern and colors signed off before the truck arrives. There is no “we'll decide on pour day” in stamping.

Curing: the step that builds strength

Concrete doesn't dry — it hydrates, gaining strength for 28 days. In heat and wind, the surface loses moisture faster than the chemistry can use it, which is how you get a weak, dusty top layer (and the scaling that follows the first winter). Three legitimate curing methods: liquid curing compound sprayed right after finishing ($0.15–$0.30/sq ft in material), 7 days under wet burlap or plastic, or ponding for small slabs. Pick one on every exterior job and name it on the quote. It costs almost nothing, almost nobody bids it, and it's the difference between concrete that hits its PSI and concrete that merely looks like it did.

Reading the supplier ticket

The batch ticket that arrives with the truck tells you exactly what you bought — learn to read it before you need to argue about it:mix design number (your 4,000 PSI air-entrained spec), slump (should match what you ordered, usually 4 in. for flatwork), batch time (concrete has about 90 minutes from batch to discharge — a late truck is rejected concrete, not a favor), and water added (the ticket records it; more than the design allows and you're pouring weaker concrete than you bid). Other ticket realities that hit the bid: short-load fees ($100–$200 under ~5 yards),Saturday pour premiums, and standby time ($2–$4/minute after the first 5–10 minutes per yard). A crew that isn't ready when the truck arrives burns money by the minute — schedule the pour, then schedule backward from it.

Run the yardage in the concrete calculator and build the itemized quote before you leave the site. Same-day quotes close concrete jobs — the client is comparing you against two other bids, and first complete bid usually wins.