What is a Soakaway and How Much Do They Cost to Build?

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We know that outdated prices are unhelpful, that’s why we last updated the price guide here on the .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:

  1. 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.
  2. 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.
  3. 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.
Soakaway Crate

A typical plastic soakaway crate with an entrance hole for drainage pipes

 

Underground pipe

Plastic underground rainwater pipe 110mm

pipe bend for underground drainage

Plastic pipe angle

Inlet for Rainwater From Guttering

Inlet for rainwater

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:

LocationSmall Business /TraderLarger Business (5+ employees)
Need a Custom Price? >Compare Up To 3 Personlised Quotes Here
London AreaN/A£950.00
South, SW and MidlandsN/A£850.00
Outer Region and NorthN/A£725.00

 




 

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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When we first created this site back in 2014, we created a poll so visitors could tell us who they thought was the least trustworthy traders in the UK.

So far, over eight thousand people have taken part in our poll.

Check out this page to see where landscape gardeners ranked in the poll results and cast your own vote. It’s free and no sign-up is required.

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Use their free service to source quotes for landscaping projects like soakaways and drainage.

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3 Responses to “What is a Soakaway and How Much Do They Cost to Build?”

  1. Brian SweeneyNovember 30, 2016 at 11:20 pm #

    Soakaways are in insult to common sense.
    If you excavate a hole in a garden it would fill up with water(fact) if you then fill that hole up with gravel it’s going to fill up twice as quick(another fact) this water then is going nowhere.if it was going to drain through the soil you wouldn’t need drainage in the first place(yet again another fact).Drainage contractors are expensive for a reason,that reason is they tend to drain the water away.Send any irate customers you have onto us,short of walking on it or turning it into wine we can do anything with water.

    • PhilFebruary 12, 2018 at 9:54 am #

      It’s slow drainage we have, water does drain through our heavy clay soil but it takes a day. A soakaway fixed the problem for us, now we no longer have a boggy garden after rain.

  2. Brian SweeneyNovember 30, 2016 at 11:22 pm #

    Really?Moderation there’s a surprise,I won’t hold my breath then!

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