How to pour a concrete driveway

Thickness

4–5 in6 in for RV or heavy vehicles

Mix strength

4,000 psiACI 332, with air entrainment

Slump

3–5 intypical flatwork

Joint spacing

8–12 ft2–3x thickness in inches, in feet

Joint depth

~25% of slab1 in on a 4 in slab

Moist cure

3–7 daysNRMCA CIP 11

Short version

• The subgrade does more for the driveway’s life than the concrete does; compact it uniformly.
• Order 4,000 psi (27.6 MPa) with air entrainment wherever freezing or deicers are a factor.
• Have enough hands on site — finishing is a race against set time, not a leisurely job.
• Cut control joints at 8 to 12 feet on a 4 inch slab, about a quarter of the thickness deep.
• Cure for 3 to 7 days, stay off it for 24 to 48 hours, and keep vehicles off for about a week.

What do you need to do before the truck arrives?

Handle permits, utilities, and drainage before you order concrete, because all three can stop a pour cold. Start with the building department — many jurisdictions require a permit for a new driveway, and a driveway that meets a public street usually involves a separate approach or curb-cut approval. See do i need a permit for a concrete driveway for how to check.

Call 811 next. The national call-before-you-dig service marks buried gas, electric, water, and communication lines at no cost, and driveways frequently run directly over service laterals.

Plan the drainage before you set a single form. The finished surface has to shed water away from the house and the garage, and common practice is a slope of about 1/8 to 1/4 inch per foot across or along the drive. Decide where the water goes at the low end, because a driveway that drains toward a garage door creates a problem that no amount of sealer fixes.

Line up your crew and your equipment. A residential driveway needs a screed board, a bull float, an edger, a groover or saw, a magnesium float, a broom, and at minimum three people who know what they are doing. Placement and finishing happen on the concrete’s schedule.

Finally, plan the washout. Concrete truck washout and rinse water are alkaline and are regulated under EPA stormwater rules — designate a containment area on site rather than letting it run to the street.

How thick should the driveway be, and what mix should you order?

Place a residential driveway 4 to 5 inches thick, and go to 6 inches where an RV, a work truck, or repeated heavy loads are expected. Depth beyond that rarely pays off on a residential slab; uniform support underneath does far more than extra inches. See how thick should a concrete driveway be for the full breakdown.

Specify the mix rather than asking for “driveway concrete.” ACI 332 calls for a minimum of 4,000 psi (27.6 MPa) with air entrainment for exterior flatwork exposed to freezing or deicing chemicals, which covers most of the country. Typical flatwork slump is 3 to 5 inches — resist any request to add water at the truck.

Reinforcement is worth including but is not a substitute for a good base. Rebar or welded wire fabric holds cracks tight after they form rather than preventing them, and spacing in residential work follows typical practice unless an engineer specifies otherwise under ACI 318.

Order 5 to 10 percent more than the calculated volume. A cubic yard covers 81 ft² at 4 inches and 65 ft² at 5 inches, and subgrade dips always take more than the math says. Running short mid-pour creates a cold joint that becomes a permanent crack. For material pricing, see how much is a yard of concrete.

How do you prepare the subgrade and set the forms?

Prepare the subgrade for uniformity above all else. Concrete tolerates a uniformly weak base far better than a base that is stiff in one place and soft in another, because differential support is what cracks slabs.

Excavate to the depth of the slab plus the base course, then strip out all organic material, topsoil, and roots. Fill and compact soft spots in lifts rather than bridging them with extra concrete. Most jobs benefit from 4 to 6 inches of compacted granular base, and in poorly draining soils that base also gives water somewhere to go.

Compact with a plate compactor in lifts, not in one pass over loose material. The test is simple: walk it: if your boot leaves a distinct heel print, it is not compacted.

Set forms of 2× lumber staked every 3 to 4 feet, with the stakes driven below the top of the form so they do not interfere with screeding. Set the forms to the drainage slope you planned, string a line, and check the whole run before you order. Coat the inside faces with a release agent so stripping does not chip the edges.

Dampen the subgrade before placement in hot weather — a dry base pulls water out of the bottom of the slab.

What happens on pour day, step by step?

Pour day runs in a fixed sequence, and each step waits on the concrete rather than the clock. Place from the far end and work back toward the truck, spreading with a come-along or shovel to roughly full depth, and consolidate against the forms so no voids remain at the edges.

Screed immediately with a straightedge riding both forms, using a sawing motion and pulling the excess forward. Then bull float the whole surface in passes at right angles to the screed direction, which knocks down ridges and embeds the coarse aggregate.

Stop and wait. Bleed water will rise to the surface, and nothing else happens until it evaporates. Working the surface with bleed water present drives that water back into the top layer and produces a weak, dusty, scaling finish.

Once the sheen is gone and the surface supports light footprints, edge the perimeter, cut or tool the control joints, and float the surface with a magnesium or bull float. Finish with a broom drawn across the direction of travel — exterior flatwork needs the traction, and hard steel troweling an exterior slab makes it slick and, on air-entrained concrete, risks surface delamination.

Where do the control joints go?

Control joints go at 2 to 3 times the slab thickness in inches, expressed in feet. A 4 inch driveway takes joints every 8 to 12 feet; a 5 inch slab takes 10 to 15 feet. Keep panels roughly square, with a length-to-width ratio no worse than about 1.5 to 1, and put a joint at any re-entrant corner where the slab changes shape.

Cut them about a quarter of the slab thickness deep — 1 inch on a 4 inch slab. A joint that is too shallow does not create a weakened plane, and the slab cracks somewhere else instead.

Timing depends on method. Tooled joints are formed during finishing while the concrete is still plastic. Saw-cut joints go in after the concrete has set enough that the saw does not ravel the edges but before shrinkage stress cracks it — early-entry saws widen that window considerably.

Isolation joints are a separate item. Where the driveway meets the garage slab, a sidewalk, a foundation wall, or a column, put a compressible isolation joint material full depth so the two elements can move independently. Slabs that are cast tight against a foundation crack at that line.

Control joints do not prevent cracking. They decide where the crack goes, which is the entire point.

How do you cure a new driveway, and when can you use it?

Cure the driveway by keeping it moist for at least 3 to 7 days, which is the minimum moist protection NRMCA’s Concrete in Practice guidance calls for. Curing is what builds strength; a slab left to dry in the sun loses surface durability permanently no matter how good the mix was.

Use whichever method suits the weather: water ponding, soaker hoses, wet burlap kept wet, plastic sheeting lapped and weighted, or a membrane-forming curing compound meeting ASTM C309. Whatever you pick, the first 24 hours matter most.

Timelines for use follow industry convention rather than a published standard. Foot traffic at 24 to 48 hours, passenger vehicles at about 7 days, heavy vehicles at 28 days. Cold weather stretches all of them, and under ACI 306 cold-weather protection protocols apply when the air temperature stays below 40 °F (4 °C) for three or more consecutive days.

Two rules for the first winter. Do not apply deicing salts — new concrete has not developed full resistance, and scaling is the result. And wait about 28 days before sealing, since sealer over construction moisture blisters.

Common mistakes

• Placing on an uncompacted or uneven subgrade — differential support cracks the slab within the first year no matter how strong the concrete is.
• Adding water at the truck to make placing easier — the extra water raises the water-cement ratio and permanently weakens the surface that takes all the wear.
• Finishing while bleed water is on the surface — the water gets worked back into the top layer and the driveway dusts and scales.
• Cutting joints too shallow or too far apart — the slab cracks on its own line instead of the one you cut.
• Salting the driveway its first winter — young concrete has not developed its full scaling resistance and the surface flakes off.