Concrete Driveways and Patios: What to Ask Before the Pour

How thick, and on what base?

Ask what thickness they plan to pour and why, what vehicles it’s designed for (a driveway that sees a truck or RV is different from a patio), and how the ground underneath will be prepared. The American Concrete Institute’s residential concrete code covers “slabs-on-ground” for one- and two-family homes (ACI 332). A good answer explains the choice for your site.

Where will the joints go?

Joints decide where a slab cracks. “Jointing eliminates unsightly random cracks” (American Cement Association).

A contraction joint is a groove that creates “a weakened plane to regulate the location of cracking”; an isolation joint is “a separation between adjacent sections of a concrete structure to allow relative movement” (ACI).
If joints are saw-cut, ACI says “cuts should typically be made within 4 to 12 hours after placing the slab, depending on the temperature and weather conditions,” and “should generally be made to one-fourth the depth of the slab” (ACI).

Ask to see the joint layout before the pour.

Will it crack?

Some cracking is normal. ACI notes that its guidance documents tell designers and contractors to advise owners that “it is normal to expect some amount of cracking and curling on every project” (ACI). Good joints, base preparation and curing keep it under control. Ask what the contractor does to limit cracking.

How will it be cured?

“The longer it is kept moist, the stronger and more durable concrete will become” (American Cement Association). Concrete can be cured “by sprinkling with water, fogging, or using moisture-retaining fabrics such as burlap or cotton mats,” or by sealing the surface “with plastic or special sprays called curing compounds” (same page). ACI adds that moisture and temperature control “reduce adverse volumetric changes that may cause cracking” (ACI). Ask which method they’ll use, and how long to stay off it.

Where will the water go?

“Inadequate drainage permits ponding,” and harmful solutions ponded on concrete “might penetrate into concrete and cause deterioration” (ACI). Ask how the slab will slope, which way water will run, and that it runs away from the house.

What reinforcement, and where?

Ask whether they’ll use rebar, wire mesh or fibers, and how it will be held in place. ACI guidance: “Welded wire reinforcement should not be placed on the ground and pulled up after placement of the concrete” (ACI).

What finish?

For walkways, driveways and pool areas, ask about slip resistance. “You can produce a slip-resistant surface by brooming before the concrete has thoroughly hardened” (American Cement Association). Stamped and colored finishes are other options.

Permits

On your lot: rules vary. The City of Santa Barbara’s permit-exempt list has a “Decks” item covering “Uncovered residential platforms, decks, porches, walks, and similar structures not more than 10 inches above adjacent grade” (with conditions). It doesn’t mention driveways or patios, so ask. The list also notes that “many of the items listed below may be regulated by other city divisions” (checklist). Grading, drainage changes and retaining walls can bring their own permits. Ask your building department.
At the street: a new or widened driveway approach is usually in the public right-of-way. In unincorporated San Luis Obispo County, “An Encroachment Permit is required whenever an activity (e.g. construction, events, etc.) takes place in the County right of way,” and “Driveway” is one of its permit types (SLO County Public Works). Cities have their own public works permits.

Who’s doing the work?

CSLB describes a C-8 concrete contractor as one who “forms, pours, places, finishes and installs specified mass, pavement, flat and other concrete work” (CSLB); general building contractors also do concrete as part of larger projects. Check the license, and see our guide on hiring a licensed contractor.

What affects the cost

Area and thickness, demolition and hauling of old concrete, base preparation and grading, reinforcement, the finish, and access for the concrete truck. See our concrete page for how a project usually goes.

Concrete driveways and patios: what to ask before the pour