A soakaway is a drainage system that allows rainwater to disperse into the ground, it’s designed to cope with sudden deluges of rain from roofs, pathways and driveways.
Without a soakaway or other similar drainage provision, the property may experience issues with flash flooding during periods of heavy rain.
On this page we’ll try to answer the following questions:
What is a soakaway exactly and how much do they typically cost to install?
What materials are required and how much do they cost?
How long should the work take?
We can also point you in the right direction so you can get your own quote.
We know that outdated prices are unhelpful, that’s why we last updated the price guide here on the
How is a Soakaway Constructed?
Most soakaways are located approximately 5 metres away from the property and around a metre or so under a lawn, patio or driveway.
The soakaway is a large hole that’s filled with plastic crates that contain a large void. This void fills with water when it rains and then slowly empties as the water seeps into the surrounding ground.
In the past, soakaways were filled with rubble but this type of system is less effective and more prone to blockages.
Soakaways can accept rainwater from any part of the home but most commonly:
- From driveways and paths
- Roof gutters
- Flat roofs
Soakaways are only used for rainwater and not human waste.
Why Install a New Soakaway?
There are several reasons why you may want (or need) a new soakaway:
- Soakaways often become blocked with roots, leaves, twigs, roof moss and mud. They also occasionally collapse due to weight (cars, lorries, concrete, tarmac etc) parked above them.
- If you construct an extension to your home, the additional rainwater from the new roof area may be too much for your existing soakaway to cope with and a separate one may need to be constructed.
- Due to recent episodes flash flooding in the UK, the building regulations have been updated to protect homes from water damage. When installing, replacing or extending a driveway, you must prevent rainwater from running off onto public footpaths and roads. A soakaway is a popular way to achieve this.
What Work Is Involved With Installing a Soakaway?
Below you find a typical works schedule for installing a rainwater soakaway.
This schedule is for the removal of an existing rubble soakaway and its replacement with a plastic crate-based system, we assume the location is under a lawn or flower bed and not a driveway.
- Excavate the ground to a depth of at least 1.2 metres by digging out the existing soakaway and removing the waste material
- Perform a water permeable test. This is to check how fast the water drains away, soil that contains too much clay may reduce the effectiveness of the soakaway.
- Lay gravel to base of hole.
- Wrap the plastic crates in a weedproof membrane and place them inside of the excavated hole, lay new drainage pipes as required, lay a weedproof membrane over and around crates.
- Fill the rest of the hole with earth, topsoil and finish off the surface as required; blocks, tarcmac or turf etc.
How Much Do The Materials Cost?
The crates cost around £35 each* and to cope with water from a 50 sq metre roof, you’ll need around five of them.
Underground pipe, angle and silt traps cost around £45
Gravel and weedproof membrane costs around £30
Equipment hire – £200
* We assume you do not need heavy duty crates, which should be used under driveways as they can support the weight of cars and vans. These cost more.
How Long Does The Work Take and What Is The Labour Cost?
If the soakaway is located under a lawn or flowerbed, it should take two people around half a day to excavate the ground and install a new soakaway.
For soakaways under concrete, blocks, tarmac or patio slabs, the work will take longer and cost more.
Below is our guide price for installing a soakaway, this is based on the information provided to us by several drainage experts and landscape gardeners.
As you can see, the average cost is around £1k but the price varies and depends on location:
|Location||Small Business /Trader||Larger Business (5+ employees)|
|Need a Custom Price? >|
|South, SW and Midlands||N/A||£875.00|
|Outer Region and North||N/A||£750.00|
Which Tradespeople Carry Out This Type of Work?
When researching the cost of installing a soakaway we reached out to landscape gardeners, builders and specialist drainage experts.
Of all the firms that responded, the landscape gardeners and builders offered us the lowest prices.
The most expensive quotes came from the drainage firms we contacted.
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