How to Plan Driveway Drainage in 2026 (UK)

How to Plan Your Driveway Drainage

1. Check the SuDS rule first. If your new driveway is non-permeable and over 5 m² draining to the road, you must drain to your own land or apply for planning permission. Permeable surfaces are exempt.
2. Test how your ground drains. Dig a 300mm test hole, fill with water and time how fast it drops. Free-draining soil suits a soakaway; clay needs a larger soakaway or a connection to a surface-water sewer.
3. Set the falls. Slope the driveway 1:40 to 1:60 away from the house and toward your chosen drainage point so water never pools against the building.
4. Choose the method. Permeable block paving or resin, a channel drain across the threshold feeding a soakaway, or a gravel sub-base that absorbs run-off.
5. Size the soakaway. Use a soakaway crate sized to the driveway area and your soil's infiltration rate — typically 1–2 m³ of crates for an average drive, set at least 5m from the house.
6. Install a threshold drain at the house. A linear channel drain (ACO type) across the garage or front door stops water entering the property.
7. Get it signed off. Keep evidence the surface is permeable (or that drainage is to your own land) for Building Control and future sale.

Sizing, Falls and Common Mistakes

Before you commit to a design, prove the ground can take the water. Dig a 300 mm test pit, fill it, let it drain, then refill and time how long the water takes to fall from 75% to 25% full — the BRE 365 percolation test. Divide that drop by the time to get your soil infiltration rate: free-draining sand may empty in minutes, while clay can take hours and effectively rules out a soakaway. As a rough guide an average 40 m² drive on reasonable soil needs roughly 1–2 m³ of soakaway crates, wrapped in geotextile and sited at least 5 m from the house and clear of foundations, trees and other drains.

Falls do the quiet work: a 1:40 to 1:60 slope running away from the building toward your channel or permeable zone keeps water off the threshold. Set the channel drain at the lowest point — usually across the garage or front-door threshold — and never trust a surface that only looks flat by eye. For permeable paving the sub-base must be an open-graded, no-fines aggregate (a Type 3 or clean angular stone), not standard MOT Type 1, or the voids clog and the surface stops draining within a few winters.

1. Connecting surface water to a foul sewer. This is illegal and overloads treatment works — driveway run-off must go to a soakaway, a surface-water sewer with consent, or a permeable area.
2. Skipping the percolation test. Guessing the soakaway size on clay leads to standing water and a drive that floods in heavy rain.
3. Falling toward the house. Even a slight reverse gradient pushes water at the garage or door; always fall away from the building.
4. Assuming permeable means maintenance-free. Porous surfaces silt up over time; brush and occasionally jet-wash them so the voids keep draining.
5. Forgetting the paperwork. Keep proof the surface is permeable, or that water drains to your own land, for Building Control and any future sale.

The rules trace back to 2008 guidance on paving front gardens: the official Planning Portal guide to paving your front garden confirms a permeable surface — or one draining to a permeable area inside your boundary — does not need planning permission, while a non-permeable drive over 5 m² draining to the road does.