Ask a concrete contractor what PSI rating they use for a residential driveway, and watch how they answer. A contractor who knows their trade will say 3,500 to 4,000 PSI without hesitating, then explain why that number changes based on your climate and soil type. One who fumbles or gives a vague answer like “the good stuff” hasn’t poured enough slabs to have an opinion worth trusting.
Homeowners often shop concrete work on price and availability alone. That’s a mistake, because concrete is unforgiving. Once it sets, mistakes in subgrade prep, mix design, or curing become permanent problems: cracking, spalling, uneven settling. The questions below are designed to expose whether a contractor actually understands the material or is just mixing bags and hoping for the best.
Start With the Mix Design, Not the Price
Before discussing cost, ask what PSI strength they plan to use and why. For a driveway in a freeze-thaw climate, 4,000 PSI air-entrained concrete is standard. For a patio in a mild climate, 3,000 to 3,500 PSI might be fine. If a contractor quotes one number for every job regardless of location or use, they’re not tailoring the mix to your conditions.
Follow up by asking about air entrainment percentage. In regions that see freezing temperatures, 5 to 7 percent air entrainment helps the concrete survive freeze-thaw cycles without cracking. A contractor who has never heard this term or can’t explain it is not someone who works in cold climates regularly.
- What PSI strength are you specifying for this project, and why?
- Will the mix include air entrainment, and at what percentage?
- Are you using fiber reinforcement, rebar, or wire mesh, and what’s the spacing?
Ask About Subgrade Prep and Compaction
Most concrete failures trace back to what’s underneath the slab, not the concrete itself. A contractor should describe a clear process: excavating to the proper depth (typically 4 to 6 inches for a driveway, more if the soil is clay-heavy), adding a compactable base material like crushed gravel, and compacting it in lifts with a plate compactor rather than dumping it all at once and tamping the surface.
Ask how they test compaction. Some contractors will mention a proctor test or at minimum a visual and physical check, like walking on the base to see if it shifts. If a contractor shrugs and says “we just pack it down good,” that’s a warning sign. Poor compaction leads to settling, and settling leads to cracks within the first two years.
Also ask about drainage slope. A driveway or patio should slope away from structures at roughly 1/4 inch per foot minimum. A contractor who can’t state this number probably isn’t grading the subgrade with any precision.
Control Joints and Reinforcement Details
Concrete cracks. That’s not avoidable, but where it cracks is controllable through proper joint placement. Ask how far apart they space control joints. The general rule is 24 to 30 times the slab thickness in feet. For a standard 4-inch slab, that means control joints roughly every 8 to 10 feet. A contractor who spaces joints randomly, or skips them on smaller sections, is inviting uncontrolled cracking.
Ask whether they use rebar, wire mesh, or fiber reinforcement, and get specific about placement. Wire mesh laid on the ground before the pour does nothing structurally; it needs to sit in the middle to upper third of the slab, which means using chairs or hooking it up during the pour. If a contractor says they lay mesh down and pour concrete directly on top, that mesh will sit at the bottom of the slab where it provides no benefit.
- How far apart will control joints be placed, and how deep will they be cut?
- What reinforcement method are you using, and how will it be positioned in the slab?
- How soon after the pour will joints be cut, and with what tool?
Weather and Curing Practices
Concrete needs moisture and moderate temperature to cure properly for at least the first 7 days, ideally closer to 28 days for full strength. Ask what happens if the forecast calls for rain the day after the pour, or if temperatures drop below 40 degrees Fahrenheit. A contractor with real experience will mention covering fresh concrete with plastic sheeting, using insulated blankets in cold weather, or applying a curing compound to slow moisture loss in hot, dry conditions.
Ask about hot weather pours specifically. Concrete poured when temperatures exceed 90 degrees can set too fast, leading to surface cracking and reduced final strength. A knowledgeable contractor might delay a pour to early morning hours or use retarding admixtures to slow the set time. If a contractor treats every day and every season the same, that’s a sign they’re not adjusting practices to protect the work.
Insurance, Permits, and References You Can Actually Check
Ask for proof of general liability insurance and, if they have employees, workers’ compensation coverage. Request the actual certificate, not just a verbal assurance. Ask whether they’ll pull the necessary permits for the project or whether that falls on you. Concrete work for driveways, sidewalks near property lines, or anything tied to drainage often requires a permit, and a contractor who avoids the topic may be trying to skip inspections.
Request three references from jobs completed at least two years ago, not last month. Concrete that looks good after 30 days can still fail within two years if the mix or prep was wrong. Call those references and ask directly whether they’ve seen any cracking, settling, or drainage problems since the work was finished.
- Can you provide a current certificate of insurance?
- Will you handle the permit process, or is that my responsibility?
- Can I get contact information for three jobs completed over two years ago?
Write these questions down and bring them to every bid meeting. Score each contractor’s answers side by side rather than relying on memory or gut feeling after the fact. The contractor who answers with specific numbers, clear processes, and no hesitation is the one who has actually done this work enough times to know what matters.
Related articles: Commercial vs. Residential Contractors: The Real Differences That Affect Your Project