Summary: Learn how to construct driveway drainage, patio drainage, a drainage system, build a driveway and patio drainage system and build a channel.
For larger patios or driveways, there may be a need for a drainage system, particularly if there is a natural slope towards the building. The ideal drain would be a linear drainage system, which consists of a U-section channel bedded in concrete and running into an existing drain or soakaway.
It is important to consider the drainage system at the same time as you plan the patio or driveway. The drainage channel should be positioned at the lowest part of the patio or driveway and have a fall of 1:40.
If the drainage channel runs into a soakaway it must be at least 3m (9ft 9in) away from the building.
When laying the patio or driveway you will leave narrow gaps for the channel in accordance with yours plan. The gap will be approximately the diameter of a drainpipe or length of guttering 100mm (4in).
Building the channel
- When the patio has set hard, line the narrow gaps in the patio with a concrete mix: 1 part cement to 3.5 parts all-in aggregate, which will include sand.
- Using a length of drainpipe, shape the concrete to a depth of about 25mm (1 in).Continue along the channel until you reach the drain or Soakaway, but make sure the gully you are creating in the concrete has no ridges so the water will flow freely.
- As you progress remove any excess concrete from the surface of the slabs or pavers.
- When you have finished it is a good idea to cover the drainage channel with planks until the concrete has set. This is to avoid cats, dogs or people walking on it and leaving imprints and ridges that prevent the water flowing freely.
- Alternatively, you can use ready-made concrete channelling that you will find at a builders’ merchants.
- Gauging trowel
- All-in aggregate
- Length of drainpipe