Most hardscaping failures trace back to water that had nowhere to go. Paving that frost-heaves, walls that bulge, and footings that settle usually sit on ground that stayed wet. Good drainage is less about a single feature and more about giving water a clear, downhill exit at every stage of a project.
Start with the grade
Before any stone, decide where water should leave. A surface that falls gently away from buildings and toward a safe discharge point will shed most rain on its own. The classic mistake is grading a patio level for comfort and trapping water against a foundation.
- Slope finished surfaces away from structures.
- Keep a continuous fall — avoid flat spots that pond.
- Direct runoff to a planting bed, swale, or municipal system, never onto a neighbour's property.
In freeze-thaw climates the spring melt is often the heaviest water event of the year. Designing for meltwater, not just summer rain, tends to size drainage correctly.
Gravel beds under paving
A compacted gravel base does two jobs: it spreads load and it drains. Open-graded angular aggregate holds little water and gives meltwater somewhere to sit below the surface rather than at it. This is the same free-draining principle used behind a retaining wall.
| Situation | Common approach |
|---|---|
| Path on draining soil | Compacted granular base, surface fall |
| Path on clay | Deeper granular base, drain to outfall |
| Wall on a wet slope | Gravel backfill plus perforated drain |
| Patio near a building | Fall away from wall, edge drain if needed |
When a French drain earns its place
A French drain is a gravel-filled trench, often with a perforated pipe, that intercepts and carries water away. It is worth the effort where water collects behind a wall, along the uphill edge of a patio, or in a low corner that stays wet. Wrapping the pipe and gravel in a geotextile keeps fine soil from clogging it over time.
- Dig a trench on a continuous fall to the discharge point.
- Line it with geotextile and add a gravel bed.
- Lay perforated pipe, holes down, on the gravel.
- Surround with more gravel and fold the geotextile over.
- Cap and connect to a safe outfall.
Surfaces that drain on their own
Gravel paths and wide-jointed flagstone let rain soak in rather than run off, which reduces the volume any drain has to carry. Pairing a permeable surface with a sound base is often simpler than channelling every drop to a pipe.
Continue reading
For the surface that sits on these bases, see laying a flagstone path. For the gravel band that drains a wall, see building a dry-stack retaining wall.