Concrete Driveway Drainage: Slope, Channels & Trench Drains

Quick Verdict

Good concrete driveway drainage starts with slope and ends with a way to catch and carry water off the slab. In rainy Oregon, the goal is simple: move water away from the house, off the concrete, and into a drain or daylight before it ponds, freezes, or runs into the garage. Most driveways need a cross-slope or pitch of about a quarter inch per foot, plus a trench drain or channel where the grade runs toward a building or the street. Get the slope and drainage right before you pour, and you avoid birdbaths, ice, and water working under the slab. Fix it after the fact and you are usually saw-cutting and retrofitting a drain.

Why Drainage Comes First in Oregon

We get a lot of water. Standing water on a driveway is not just a puddle — it is the start of most concrete problems here:

• Water under the slab. Ponding water finds joints and edges, saturates the sub-grade, and undermines support. On Willamette Valley clay that holds water, the base softens and the slab settles or cracks.
• Freeze-thaw damage. East of the Cascades and in the Gorge, water that sits and freezes pries at the surface and joints, causing spalling and cracks.
• Ice and safety. A flat or back-pitched driveway sheds water toward the garage or house, where it pools and freezes into a hazard.

That is why drainage is designed before the pour, alongside the sub-grade prep that drains. For the full picture of how a driveway is built, see our Oregon concrete services guide.

Slope: The First Line of Defense

Before any drain, the driveway itself must be graded to move water. There are two kinds of slope to plan:

• Running slope (pitch). The slope along the length of the driveway. Ideally it pitches away from the house toward the street or a low point.
• Cross-slope (crown or tilt). A side-to-side tilt that pushes water to one edge or to a center crown so it runs off rather than sitting in the middle.

A common target is roughly a quarter inch of fall per foot — enough to drain, not so steep it is uncomfortable to walk or park on. Driveways that slope toward the garage are the problem cases. When you cannot regrade enough to pitch water away, you add a drain to intercept it.

When Slope Alone Is Not Enough

Some sites cannot drain by slope alone — a driveway that runs downhill into a garage, a low spot between the house and the street, or a long flat approach. Those need a collection drain.

Trench Drains and Channel Drains

A driveway trench drain (also called a channel drain) is a long, narrow grate set flush with the concrete that catches sheet water across its full width and carries it to a pipe. It is the workhorse of driveway drainage in our climate.

• Across the garage apron. The most common spot. A trench drain just outside the garage door intercepts water before it can run inside.
• At the low point. Where the grade collects water, a channel drain catches it and routes it to daylight or a storm connection.
• At the street edge or property line. To keep your runoff from sheeting onto a sidewalk or neighbor.

Channel drains are sized to the water they must carry, set to the right slope inside the channel, and tied to an outlet pipe. They get cast into the pour, so they belong in the plan from the start.

Cost Considerations

Drainage adds cost, but far less than fixing a flooded garage or a settled slab later.

Industry Baseline Range: adding a cast-in trench drain to a new driveway pour typically runs in the range of $40 to $120 per linear foot installed, depending on the channel system, depth, and how far the outlet must run+. 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

Retrofitting drainage into an existing slab costs more than building it in, because it means saw-cutting, demo, and patching. If you are pouring new concrete anyway, designing the slope and drain now is the cheap moment to do it. Oregon's May-to-October pour window also means drainage details get locked in early, when crews schedule the season's work.

Tie-In to the Bigger Drainage Picture

Driveway drainage does not end at the slab edge. The water you collect has to go somewhere legal and effective — to daylight on your own property, to a dry well or infiltration area where soil allows, or to an approved storm connection. On clay soils that do not absorb well, that often means piping to a lower outlet rather than relying on the ground to soak it up. Plan the whole path, not just the grate.

Proper joints matter here too: water exploits cracks, and well-placed control joints explained keep cracking where it belongs instead of opening random paths for water. If your current driveway already cracks where water collects, our guide on why concrete driveways crack connects the two.

The Bottom Line

Concrete driveway drainage is slope first, drains second. Pitch the slab a quarter inch per foot away from the house, add a cross-slope so water runs off, and put a trench drain wherever the grade pushes water toward a building or a low spot. Design it before the pour and tie it to a real outlet. Cojo builds drainage into every concrete services job across the Willamette Valley and the Gorge. If your driveway floods, ices, or runs into the garage, request a drainage assessment and we will map a fix.