A concrete driveway poured wrong will crack within two years, and you’ll pay twice to fix what should have been done once. Concrete work looks simple from the curb: a truck shows up, gray mud gets poured into forms, and a few days later you have a slab. What actually determines whether that slab lasts 30 years or 3 happens before the truck ever arrives, in decisions about licensing, mix design, and who’s standing on your property with a trowel. Here’s how to vet a contractor before you sign anything.
Verify the License and Insurance, Not Just the Pitch
Every state handles contractor licensing differently, but the baseline check is the same everywhere: pull the license number and confirm it’s active, in good standing, and actually covers concrete or flatwork. In Washington, for example, contractors must carry a $12,000 bond and general liability insurance, and you can verify both through the Department of Labor and Industries website in about two minutes. Don’t take a business card’s word for it. Look up the number yourself.
- Confirm the license is current, not expired or suspended.
- Check for a history of complaints or unpaid judgments against the license.
- Ask for proof of general liability insurance, ideally $500,000 to $1,000,000 in coverage.
- Ask if workers are covered under workers’ compensation, especially if subcontractors will be on site.
If a contractor hesitates to provide a license number or insurance certificate, that hesitation is the answer. A legitimate operation hands this information over without friction because they deal with the request weekly.
Get Three Bids and Read Them Line by Line
Bids that differ by more than 20 to 30 percent usually mean someone is cutting a corner you haven’t spotted yet. Collect at least three written estimates and compare them item by item instead of just looking at the bottom number. A bid worth trusting spells out the following:
- Square footage and slab thickness (4 inches for walkways and patios, 5 to 6 inches for driveways carrying vehicle loads).
- Base preparation, including how many inches of compacted gravel will go down before the pour.
- Concrete mix specifications, including PSI strength and slump.
- Reinforcement type: wire mesh, rebar size and spacing, or fiber reinforcement.
- Control joint layout and spacing.
- Cleanup, demolition of old concrete if applicable, and disposal fees.
- Payment schedule and total timeline from prep to final cure.
A one-page quote with a single lump sum and no breakdown tells you the contractor either doesn’t plan the job in detail or doesn’t want you comparing it to competitors. Either way, ask for specifics before you pay a deposit. Most reputable contractors ask for 10 to 30 percent down, with the balance due on completion, not before.
Know the Mix Specs Before the Truck Arrives
Concrete isn’t one product. It’s a formula, and the formula has to match the job. Residential driveways and patios typically call for 3,500 to 4,000 PSI concrete, while sidewalks and light-use patios can sometimes get by with 3,000 PSI. If your contractor can’t tell you the PSI rating they’re ordering, they haven’t thought about the load the slab needs to carry.
Slump measures how wet or stiff the mix is before it sets, tested in inches of settling from a standard cone. A slump of 4 to 6 inches is normal for flatwork. Anything higher means extra water was added at the site to make the pour easier to finish, which weakens the final strength significantly. Every gallon of water added beyond the design mix can cut compressive strength by several hundred PSI. If you see a driveway crew adding water from a hose right before pouring, that’s a mix getting diluted in front of you.
Air entrainment matters in any climate with freeze-thaw cycles. A mix with 5 to 7 percent entrained air resists the cracking that comes from water expanding inside the slab during winter. Ask directly whether the mix includes an air-entraining admixture if you live somewhere that sees frost.
- PSI: 3,500 to 4,000 for driveways, 3,000 to 3,500 for patios and walkways.
- Slump: 4 to 6 inches at the truck, not after water gets added on site.
- Air entrainment: 5 to 7 percent in freeze-thaw regions.
- Reinforcement: #3 or #4 rebar on 16 to 18 inch centers, or 6×6 wire mesh for lighter loads.
- Control joints: spaced at roughly 2 to 3 times the slab thickness in feet, so a 4 inch slab gets joints every 8 to 12 feet.
Red Flags That Signal a Bad Pour
Some warning signs show up before a shovel hits the dirt. Others show up on pour day, and by then it’s harder to stop the job without losing money. Watch for these patterns:
- A contractor who refuses to put specs (PSI, thickness, reinforcement) in writing and insists you just “trust the crew.”
- Pouring directly over loose or uncompacted soil without a gravel base, which leads to settling and cracking within a year or two.
- No control joints planned, or joints cut too far apart for the slab thickness.
- Adding water to the mix at the site to speed up finishing, which anyone can see happening if they’re paying attention.
- Pouring in temperatures below 40 degrees without any cold-weather protection like insulated blankets or heated enclosures.
- Finishing crews who rush the cure and strip forms or open the slab to traffic in under 24 hours.
- No mention of curing method at all. Concrete needs to stay moist for at least 7 days to reach useful strength, through wet curing, curing compound, or covering.
Any one of these alone might have an explanation. Two or more together usually means the crew is working fast to get to the next job, not working carefully to get your job right.
Check References the Right Way
Ask for addresses, not just names and phone numbers, so you can drive by and look at work that’s had time to cure and settle. A slab poured last month tells you almost nothing. A driveway poured three years ago that’s still flat, crack-free, and draining properly tells you everything. When you call references, ask specific questions instead of general ones.
- Did the crew show up when scheduled, and did the job finish on the timeline promised?
- Were there any cracks, discoloration, or settling issues after the first winter?
- Did the final invoice match the original bid, or were there surprise charges?
- Would they hire the same crew again for a second project?
If a contractor can only offer one or two references, or if the references are all from more than five years ago, that’s a sign the business may not have steady repeat work, which is worth knowing before you hand over a deposit.
Next Step
Before you sign a contract, get the PSI, slump, thickness, and reinforcement specs in writing, confirm the license and insurance independently, and drive by at least one past job that’s older than two years. If you’re in the south Puget Sound region and want a crew that puts these specs in writing without being asked twice, Olympia Concrete Contractors is a solid place to start your comparison. Whoever you choose, treat the bid review as the real work of hiring, because the pour itself is the easy part once the planning is right.
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