Quick Verdict
To grade a patio or shed pad for drainage in Oregon, you build the subgrade with a slight, consistent fall so the finished surface sheds water away from the house or shed floor. That means cutting and filling the pad to a small slope, typically a modest fall per foot, compacting the subgrade, setting base rock to grade, and adding an edge swale where the water needs a path out. Get the earthwork fall right and the patio or shed pad drains on its own; skip it and you trap water against your structure. This is the dirt-work side; the drainage-system design lives on the drainage pillar.
Why the Earthwork Fall Matters Most
A patio or shed pad fails at drainage long before the pavers or the shed go down, in the dirt. If the subgrade is flat or, worse, tilted back toward the house, no surface material will fix it. Water follows grade, and grade is set in the earthwork.
The job is to give the pad a slight, deliberate fall away from any structure so water runs off instead of pooling. A small slope is plenty, a modest fall per foot is the usual target, enough to drain without being noticeable underfoot. The rest of this page is about building that fall correctly. For the wider topic of moving water across a property, see our grading and drainage earthwork guide, and keep the system design (drains, pipe, outlets) on that pillar.
Cutting and Filling the Pad to Slope
You establish the fall by shaping the subgrade, not by hoping the base rock evens out.
- Strip the topsoil and any organic material; pads do not sit on sod or loam.
- Cut the high side and fill the low side to create a continuous, gentle slope away from the structure.
- Set the fall so the surface drains to an edge that has somewhere to go, never toward the house wall or the shed floor.
- Keep the slope consistent; a wavy pad ponds in the dips.
The finished subgrade should already drain before any rock goes on. The base layer follows the shape you cut; it does not create it.
Compacting and Base Rock
A pad that is not compacted settles, and a pad that settles loses its fall and starts ponding. Compaction is what makes the grade hold.
| Step | Purpose |
|---|---|
| Compact subgrade | Stop future settlement that would flatten or reverse the fall |
| Place base rock (crushed gravel) | Stable, draining foundation for pavers, slab, or shed |
| Compact base in lifts | Build strength without trapping soft layers |
| Verify fall after compaction | Confirm the finished grade still sheds water |
Keeping Water From Running Back
The single most important rule: water must never drain toward the house or into the shed. A pad that slopes the wrong way funnels rain straight to your foundation or floor.
- Always pitch the fall away from structures, toward the open yard or a controlled outlet.
- Where the pad sits in a low area or against a slope, add an edge swale, a shallow graded channel, to intercept water and carry it around the pad.
- Make sure the water you shed off the pad has somewhere to go and is not just dumped where it pools again.
The swale is the simple earthwork tool that handles the cases where slope alone is not enough. Beyond the pad, blending the grade into the surrounding yard is the finish-grading work covered in finish grading a lawn.
Oregon Conditions for Pad Grading
Oregon ground makes the fall and compaction matter more than in drier climates.
- Clay pad subgrade that pumps. Wet Willamette Valley clay turns soft and "pumps" under load when saturated. A pad built on unprepared wet clay settles unevenly and loses its drainage fall. Compaction and base rock are not optional here.
- Frost protection east of the Cascades. In Central and Eastern Oregon, a saturated, frost-susceptible pad heaves in winter. Keeping the section drained and using non-frost-susceptible base reduces heave.
- The dry window to set base. The May-to-October dry season is the time to cut and compact a pad; wet-season subgrade is harder to compact and easier to ruin.
- Gentle fall on flat valley yards. On dead-flat lots, even a small, carefully built fall is what keeps a patio from ponding, because there is no natural slope to help.
Common Pad-Grading Mistakes
Most pad drainage failures trace back to a handful of avoidable mistakes, almost all of them made in the earthwork before the surface goes down.
- Building on topsoil or organics. Pads set on sod, loam, or roots settle as the organic material breaks down, ruining the fall. Strip down to firm soil first.
- Skipping compaction. An uncompacted subgrade, especially wet clay, settles unevenly and turns a graded pad into a ponding one. Compaction is what makes the fall hold.
- Sloping toward the structure. A pad pitched back toward the house or shed funnels water to the foundation or floor. The fall must always go away from structures.
- No outlet for the water. Shedding water off the pad into a spot where it just pools again solves nothing. The water needs a path to daylight or a swale.
- Too flat to drain. A "level" pad ponds. Even a patio needs a slight, deliberate fall built in; flat is not the goal, gentle slope is.
Avoiding these comes down to doing the dirt work right: strip, slope, compact, and give the water somewhere to go. A pad that fails on drainage almost always skipped one of those steps, and fixing it after the surface is down means tearing it back up. Getting the earthwork right the first time is far cheaper than the redo.
Current Market Reality
Pad grading cost tracks the pad size, the cut-and-fill volume, the base depth, and access. A small, simple shed pad is a short job; a large patio with imported base and a swale is more.
Industry Baseline Range: grading and leveling commonly runs $0.75 - $4.00+ per square foot, with crushed gravel base delivered at $45 - $110+ per cubic yard, plus a $250 - $800+ mobilization and a $500 - $1,500+ minimum on small jobs. A typical patio or shed pad with cut, compaction, and base lands accordingly.
These are industry baseline ranges for planning only -- actual pricing depends on site conditions, soil, access, depth, haul-off, and current market conditions. Get a site-specific quote.
The Bottom Line
A patio or shed pad that drains is built in the dirt: a slight fall away from structures, a compacted subgrade, base rock to grade, and an edge swale where the slope alone cannot carry the water out. In Oregon clay and frost country, the compaction and drainage are what make it last. Cojo grades pads to drain right the first time. See our excavation services, read the Oregon excavation contractor guide, and request a free estimate.