San Jose sits on clay. Not all of it, but a lot of it, especially in the older flatland neighborhoods like Rose Garden, Willow Glen, and Naglee Park, where the soil is heavy adobe clay that was farmland or orchard before it was a street. Clay like that swells when it's wet and shrinks when it's dry, sometimes by an inch or more across a season. A contractor who doesn't grade for that, or who skips a proper base, is setting you up for a driveway that heaves at the garage apron or a patio slab that tips toward the house instead of away from it. This is the first thing to ask anyone bidding your job: what do they know about the dirt under your specific lot.

Newer subdivisions out toward Evergreen or the Coyote Valley side tend to have engineered fill, compacted and more predictable, but even there the base under a slab still needs to be built, not assumed. And if you're near Alviso or the baylands, you're dealing with a higher water table and sandier soil that behaves completely differently. A contractor who works the whole valley should be able to tell you which kind of ground you're on without pulling out a map.

Check the license, and actually look it up

Every concrete contractor working in California needs a CSLB license, C-8 for concrete specifically, or a general B license if the concrete work is part of a larger job. Don't take someone's word for it. The CSLB website lets you search the license number and see if it's active, what class it covers, and whether there are any complaints or bond issues against it. This takes two minutes and it's the single easiest way to rule out a fly-by-night operation before you hand over a deposit.

Ask for proof of general liability insurance too. Concrete work involves saw cutting, heavy trucks, sometimes removal with a jackhammer or mini excavator, and if something goes wrong on your property, like a cracked sewer lateral or a damaged fence, you want to know the contractor's insurance covers it and not your homeowner's policy.

Read the bid like it's an instruction manual

A real bid for a slab, driveway, or patio should tell you the thickness of the concrete, usually 4 inches for a patio or sidewalk and 5 to 6 inches for a driveway that'll take vehicle weight. It should say whether they're using rebar or wire mesh for reinforcement, and for anything load-bearing, rebar on chairs, not mesh laid on the dirt and hoped for the best, is the better call. It should mention the base, typically 4 inches of compacted aggregate base rock under the slab, more if the existing soil is soft or has organic material in it that needs to come out first.

It should also say where the control joints go and how deep they're cut. Concrete cracks. That's not a defect, that's what the material does as it cures and shrinks. The job of a control joint is to tell the crack where to happen instead of letting it pick its own spot across the middle of your new patio. Joints are usually saw-cut within 24 hours of the pour, spaced roughly 2 to 3 times the slab thickness in feet, so an 8 to 10 foot spacing is typical for a 4-inch slab. If a bid doesn't mention joint layout at all, ask about it directly.

Cure time matters more than people expect

Concrete reaches most of its working strength in about 28 days, but you don't have to wait that long to use it. Foot traffic is usually fine after 24 to 48 hours. Driving a car on a new driveway generally needs 7 days minimum, sometimes longer if a contractor pushed the pour during a cold snap in December or January, since cold slows the cure. San Jose doesn't get hard freezes often, but a contractor who pours in the rainy season, November through March, needs to know how to protect a fresh slab from a downpour before it sets, and how to cover it if rain shows up sooner than the forecast said.

Ask about permits before they do

The City of San Jose, and the individual cities around it like Santa Clara, Campbell, and Los Gatos, generally require a permit for structural concrete work like a new foundation, a retaining wall over a certain height, often 3 or 4 feet depending on what's above it, or any slab that involves changing drainage patterns on the lot. A simple patio replacement often doesn't need one. A new driveway approach that touches the sidewalk or curb usually does, because that's public right-of-way and the city inspects the base and the finish grade before it's poured. A contractor who's done this before will bring up the permit question themselves rather than waiting for you to ask, and they'll know whether your neighborhood has an HOA that also wants to approve the work, which is common in some of the newer planned developments on the east side but rare in the older grid neighborhoods near downtown.

If a bid is noticeably lower than everyone else's, ask what's missing. Sometimes it's simply a leaner profit margin. More often it's a thinner base, no rebar, or the permit and inspection cost quietly left out, which becomes your problem later when you go to sell the house and the buyer's inspector notices the driveway was never permitted.

Walk away signs

  • No physical address or a P.O. box only, no local jobsite you can drive by and look at.
  • Pressure to sign and pay a large deposit same day. California law caps a contractor's deposit at 10% of the contract price or $1,000, whichever is less, for most residential jobs.
  • A bid with no thickness, no reinforcement type, no joint spacing, just a total price.
  • Reluctance to give you a CSLB license number, or a number that doesn't match the business name.
  • No mention of the soil at all, especially on an older lot with mature trees, since roots and old tree removal can leave voids under a slab that need to be dealt with before pouring.

What a good contractor actually looks like

They'll walk the site before quoting a number. They'll ask about drainage, where your downspouts go, whether the lot slopes toward or away from the house. They'll tell you if your existing concrete needs to come out first, and what that removal involves, since a driveway with a failed base often can't just be resurfaced, it has to be broken up and hauled off. They'll give you a realistic timeline, including weather delays, because a pour scheduled for late January in a wet year might slip a week or two, and that's a sign of honesty, not disorganization.

Concrete is not a glamorous material and there's not much to hide behind once it's poured. Get the base right, get the reinforcement right, cut the joints in the right places, and it'll outlast the house around it. Skip any one of those steps and you'll be looking at a cracked slab or a heaving driveway in a few years, usually right when San Jose's clay soil goes through its first real wet winter. If you want a second opinion on a bid you've already got, or you're starting from scratch, our page on Omega Concrete has more on how we handle site prep and the kind of jobs we take on around the South Bay.