Gravel driveway drainage and soakaways

Drainage for gravel driveways: channel drains, gullies and soakaways for clay soils and drives falling to the house. How it works and typical UK prices.

In short: Gravel drive drainage covers channel drains, gullies, French drains and soakaways that deal with water where the ground cannot absorb it, usually on heavy clay or where a drive falls towards the house or garage. It suits drives that puddle, flood or wash out. A soakaway typically costs £600 to £1,200 and channel drains roughly £40 to £100 per metre in the UK.

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Gravel itself is permeable, but water still has to go somewhere once it has passed through the stone and sub-base. On free-draining sandy or chalky soils it simply soaks away. On heavy clay, or where the drive is laid on compacted made ground, water can sit in the sub-base, soften it and cause the drive to sink and rut. Drives that slope towards a house, garage or doorway need water intercepted before it reaches the building.

The usual tools are a fall built into the sub-base, a channel drain or gully at the low point, perforated pipe in a stone-filled trench, and a soakaway or connection to a suitable surface water drain. Soakaways in England and Wales are usually designed to BRE Digest 365, which uses an on-site percolation test. Water from a drive should not be connected to a foul sewer.

What is included

Assessment of falls, soil type and where water currently collects
Percolation test where a soakaway is being considered
Channel drains across thresholds or at the foot of a slope
Gullies and pipework laid to fall
Perforated land drains or French drains in stone-filled trenches
Soakaway crates or rubble-filled soakaways wrapped in geotextile
Connection to an approved surface water outlet where available

Who it is for

Drives on heavy clay that puddle or stay soft after rain
Drives that fall towards the house, garage or a doorway
Drives at the bottom of a slope that collect run-off
Existing gravel drives with sinking, wet patches
Properties where water from the drive runs onto the road

How much does it cost?

As a guide, a soakaway for a domestic drive usually costs around £600 to £1,200, channel drains roughly £40 to £100 per metre installed, and French drains about £30 to £80 per metre, depending on depth and ground conditions. See our full cost guide.

How it works

How gravel driveway drainage and soakaways works, step by step

Find the problem

Levels are taken and the ground checked to see where water collects and why it is not draining.

Test the ground

Where a soakaway is planned, a percolation test shows how fast the soil absorbs water and how big it needs to be.

Install the drainage

Channels, pipes and the soakaway are laid to fall, surrounded with stone and wrapped in geotextile.

Rebuild and finish

The sub-base is reinstated and compacted over the drainage, then the gravel surface is relaid.

Gravel driveway drainage and soakaways: FAQs

Does a gravel driveway need drainage?

Many do not. On free-draining ground with a sensible fall away from the house, water passes straight through the gravel and sub-base into the soil. Drainage is needed on heavy clay, where water collects at a low point, or where the drive slopes towards a building. A survey of the levels and soil is the way to decide.

What fall should a gravel drive have?

Even though gravel is permeable, a gentle fall in the sub-base away from the house helps water clear. Falls of around 1 in 40 to 1 in 80 are commonly used for driveways. The finished surface should also stay at least 150mm below the damp-proof course of the house, unless a drainage channel is fitted at the threshold.

How close to the house can a soakaway be?

Building Regulations guidance in England (Approved Document H) says soakaways should normally be at least 5 metres from a building and from a boundary, so water does not undermine foundations or flood a neighbour. Very small plots may not have room, in which case other options such as permeable sub-bases or a surface water connection are considered.

Can I drain my driveway into the sewer?

Water from a driveway should never go into a foul sewer. In some areas there are separate surface water sewers, but connecting to one usually needs consent from the water company. A soakaway, permeable construction or draining to a lawn or border is generally preferred, in line with sustainable drainage principles.