How Thick Should a Concrete Driveway Be? (Oregon)

Quick Verdict

A standard residential concrete driveway in Oregon should be 4 inches thick for cars and light vehicles, and 5 to 6 inches if it will carry RVs, trucks, trailers, or other heavy loads. But thickness alone does not make a driveway last — the sub-grade prep and reinforcement underneath matter just as much. On our wet Willamette Valley clay, a 6-inch slab on a bad base will fail faster than a 4-inch slab on a good one. Match the thickness to your heaviest regular load, prep the base properly, and reinforce for that load. This guide explains the 4 vs 6 inch decision and why the base is half the answer.

The Thickness Rule of Thumb

For most Oregon driveways, the standard is simple:

Use	Recommended Thickness
Cars, SUVs, light pickups	4 inches
RVs, large trucks, trailers	5–6 inches
Commercial / heavy equipment	6 inches or engineered

Four inches is the baseline residential standard and handles everyday passenger vehicles fine. The jump to 5 or 6 inches is about the heaviest thing that parks or drives on it regularly — a motorhome, a loaded trailer, a work truck. If you have or plan to have any of those, build for them now; you cannot add thickness later. Where thickness fits with the rest of the build is in the concrete services overview.

4 vs. 6 Inch: What Actually Changes

Going from 4 to 6 inches adds 50 percent more concrete, so it costs more — but it roughly doubles the load the slab can carry and adds a real margin against cracking. The honest framing:

• Stay at 4 inches if it is passenger vehicles only and the base is well prepped. Spending on 6 inches here is usually wasted.
• Go to 5–6 inches if RVs, trucks, or trailers are in the picture, or if you want extra margin on questionable soil. This is where the upgrade earns its cost.

The mistake is going thick to compensate for a bad base. A thick slab on unprepared clay still cracks — it just cracks a little later.

The Base Is Half the Answer

Here is what thickness guides from dry climates skip: in Oregon, the sub-grade decides as much as the slab. Our clay holds water and moves seasonally, and a slab of any thickness poured on bare or poorly drained clay will move and crack. A proper driveway gets:

• The soft topsoil and clay removed.
• A compacted gravel base for drainage and a stable platform.
• That gravel compacted in lifts so it does not settle.

This invisible work is exactly what cut-rate crews skip to win a bid. Do not let thickness become a distraction from the base — read sub-grade prep before you compare bids. The right answer is correct thickness and a proper base, not one or the other.

Reinforcement for the Load

Thickness and reinforcement work together. A 4-inch residential driveway often uses wire mesh; a thicker slab carrying heavy loads typically uses rebar for added strength and to hold the slab together if it cracks. The reinforcement should match the thickness and the load — covered in rebar vs. wire mesh. Under-reinforcing a thick slab wastes the thickness; the two are a package.

Cost Implications

Industry Baseline Range: going from a 4-inch to a 6-inch driveway commonly adds in the range of 15 to 30-plus percent to the concrete and reinforcement cost, on top of the base flatwork price of roughly $8 to $16 per square foot installed+. These are industry baseline ranges for planning only — actual pricing depends on lot size, access, condition, and current market conditions. Get a site-specific quote.

Current Market Reality

Concrete and rebar prices track the construction market, so the cost of stepping up thickness moves with them. The smart spend is matching thickness to your real load and putting the rest into proper base prep — over-thickening a slab on a bad base is paying more to fail a little slower. A contractor who walks your site can tell you which thickness your use actually needs.

The Bottom Line

Four inches for cars, 5 to 6 inches for RVs and trucks — but only on a properly prepped base with reinforcement matched to the load. In Oregon, the base is half the answer, and a thick slab on bad clay still cracks. Build for your heaviest regular load and put real money into the prep. For the broader concrete picture, start at our concrete services overview.

Cojo is CCB Licensed and Insured, based in Hood River, and pours driveways spec'd for your loads across the valley, the Gorge, and the I-5 corridor. Explore our concrete services and request a quote — we will recommend the thickness, base, and reinforcement for how you use the drive.