5 Questions to Ask a Concrete Contractor Before They Pour

Most "questions to ask a concrete contractor" lists tell you to ask about license and insurance. Those matter, but any pro who answers "no" to those questions has already screened themselves out of your shortlist. If you're at the pre-pour walk-through and you're deciding whether to sign the contract, ask these five questions instead. The answers will tell you more about the finished product than any Google review.

1. What PSI is the mix, and what's the aggregate size?

For a residential driveway or patio in North Carolina, the answer you want is 4,000 PSI with 3/4-inch aggregate. If the pro says 3,000 PSI, they're using a mix rated for interior slabs and it's not going to hold up to sun, freeze, and vehicle load the way 4,000 will. If they hedge or say "whatever the plant sends," they're not paying attention to the mix design and that's the single strongest predictor of a slab that fails early. This one question separates the pros who care from the ones who don't.

2. How thick is the pour and what's the reinforcement?

For a residential driveway, the answer you want is 4 inches minimum, 5 inches under any spot a heavy vehicle sits, with fiber-mesh reinforcement in the mix or rebar on 12-inch grid. Under 4 inches is too thin for NC soil movement. No reinforcement is a shortcut that will show up as diagonal cracks within 3-5 years. If a pro quotes you a 3-inch pour with no rebar and no fiber, you're getting the cheap version — and it's cheap for a reason.

3. What are you doing for the sub-base?

The answer you want: excavation down to firm subsoil, then 4 inches of compacted crushed stone (ABC or #57), compacted in lifts with a plate compactor. If the pro says "we'll pour right on the dirt" or "we'll grade it and pour" — walk away. Sub-base is the single biggest predictor of whether your slab is still flat in 15 years. In NC red clay, skipping the stone base is the fastest way to turn a $12,000 driveway into a $12,000 crack farm.

4. What's your curing plan?

The answer you want, in detail: for a summer pour, wet-cure with plastic sheeting or curing compound for at least 5 days, and cover any control joints with sealant after 30 days. For a winter pour, insulated blankets over the slab for at least 3 days if temperatures drop below 40°F. If the pro says "we finish it and leave" — that slab will lose 20-30% of its potential strength to fast drying, and you'll never know it until year 5 when it starts spalling.

5. Who does the finish work — you or a sub?

Concrete finishing is skilled labor. The person running the trowel decides how flat, how smooth, and how durable the top layer is. If the crew that shows up on pour day is a different crew than the one who bid the job, you don't know what you're getting. Ask specifically who will be doing the finish. If it's a sub, ask how long that person has worked with them and whether you can see a job they finished. Rotating finishers is the reason two houses on the same street with the same contractor get different-quality slabs.

If you get straight, confident answers to all five, you're hiring the right pro. If they hedge on more than one, keep looking.