How to Build a Garden Soakaway

What is a soakaway?

A soakaway is a type of drainage system consisting of a large hole filled with gravel and rubble that allows surface water to naturally drain back into the ground from where it gathers. It is one of the most efficient ways to deal with surface water that may collect around your home and is a very eco-friendly drainage system that can be built without hiring a professional contractor.

Most soakaways are installed around the perimeter of a home, usually in a garden, and are intended to remove excess water that normal drainage systems struggle to deal with. The process of building a soakaway is relatively straight-forward, requiring little labour and some basic materials to complete.

How does a soakaway work?

Soakaways follow a basic yet highly effective design that allow excess surface water to be slowly removed. By digging a hole and adding the materials with drainage properties, a soakaway gradually absorbs surface water deep into the earth, after which it is naturally re-distributed into the soil.

Without a soakaway, surface water has no way of draining, causing it to remain stagnant, which may lead to polluted water and even cause damage to building foundations and lawns. For example, if you attach a soakaway to a roof gutter, you can drain away surface water that would normally cause damage or dampness if left to accumulate.

The size of a soakaway depends entirely on the amount of surface water that gathers in the problem areas of the garden. Therefore, it is very important to plan out a soakaway system prior to installing it to ensure it is a suitable size and works properly.

Reasons to Build a Soakaway

The most common reason for building a soakaway is due to waterlogging in a garden, driveway, roof, or any other outdoor part of a property. Water can gather at various sections of a home property is there is not a nearby sewer or watercourse, causing waterlogging and various problems related to this.

Another reason to build a soakaway is you have heavy-duty landscaping planned, such as building a driveway. In this case, the surface water that gathers on the driveway needs to be effectively drained, with a soakaway being a suitable option if there is no access to a conventional drainage system.

When water gathers near your home due to poor drainage, it may lead to damp and mould developing. This is a problem that becomes more worse the longer it’s left untreated, so building a soakaway that drains waters away from your home is a good way to avoid dampness developing inside your property.

Planning a Soakaway

You should always take the time to plan a soakaway well in advance. While it’s simple enough to install, overlooking any aspect of the planning phase may cause the drainage system to become ineffective.

Also, different approaches are required depending on the waterlogging issue. For example, if it’s a roof that needs a suitable drainage system, you’ll need to attach it to the gutter, while it’s also possible to connect a soakaway to a French drain located in your garden.

Furthermore, there are some building regulations that must be complied with prior to installation, while you need to determine the safest location for building the soakaway. For instance, a soakaway needs to be constructed at least 5m away from external walls, which is why it’s installed around the perimeter of a property, typically in the garden.

Designing a Soakaway

The first stage of planning a soakaway is to design the drainage system. This includes the types of materials you are going to use, the length of pipe required, and the makeup of the ground in your garden.

For example, a soakaway must be built using granular materials with drainage properties, otherwise it won’t work. Therefore, you cannot build a soakaway in clay, as this won’t absorb any surface water but cause even more to gather.

Measure the distance from your external walls to the designated area for your soakaway, ensuring that it is at least 5m away from any building. Because of this, the bottom of a garden is often viewed as the best location for a soakaway.

At the same time, you may want to avoid building a soakaway too far from your home, as it means you need to buy more piping that may not be necessary. Again, providing that the soakaway is 5m from a property you are fine, so don’t feel you have to extend this further due to the size of your garden.

Building Regulations

Prior to starting your soakaway, you must check that the structure complies with local building regulations. Most people should have no issue complying with their local building regulations, as soakaways generally within guidelines.

Where to Install a Soakaway

A previously mentioned, a soakaway must be 5m away from any building where people live, so you can’t have it near your or a neighbour’s external walls. In most cases, this means building the soakaway in your garden.

It is also recommended to build a soakaway at the lowest part of the intended drainage area, as this ensures the surface water naturally drains into soakaway and doesn’t gather anywhere else. Also, make sure the soakaway is built on the softest turf for effective drainage – doing so on hard surfaces just means you’ve built a hole that will store the water rather than drain it.

Building a Soakaway

To build a soakaway, you will need the following

  • Drainage pipe
  • Shovel or Hired Mini Digger
  • Stone infill
  • Landscaping fabric


The amount of drainage pipe depends on the location of your soakaway, so make sure you calculate this prior to purchasing this material.

Make sure the drainage pipe as a diameter of at least 75mm, which is the minimum amount required for a surface water drainage system. However, drainage pipe with a 100mm diameter is generally preferred as it makes the draining more effective, so always try to go for this size when possible.

While it’s possible to build a soakaway by using a shovel, this makes the process quite labour intensive, even if the trenches and pits are shallow. If possible, consider hiring a mini digger for a few days, as this make the entire process much easier.

Stone infill should be either gravel or clean rubble, although you it’s a good idea to use a combination of both materials, espiecally if you have some lying around from previous landscaping projects.

The landscaping fabric should be any heavy-duty material such as tarpaulin or polythene, which is going to be placed on top of the gravel and rubble mixture.

Digging the Trench

The first step for installing a soakaway is to dig a trench. This is where the drainage pipe will be installed, running along to the pit where the main portion of the soakaway is located. As mentioned, this can be dug out by hand using a shovel, but it may take some effort!

The location of the trench depends on where the soakaway is draining water from. For example, it should run towards a roof gutter when draining a roof, or near a French drain if used to drain from a ground surface.

Digging the Soakaway Hole

Before you dig this hole out, consider the size you require. In most cases, it’s recommended that the hole be at least 1m x 1m x 1m, and that the hole is located below any incoming draining pipes from the trenches.

Remember, you are going to want to relay any turf when digging on a lawn, so try to carefully cut away the grass in thick strips, as this makes it much easier to reapply once the soakaway is completed.

Once the hole is dug to the correct depth, add a layer of gravel at the base, approximately 1000mm. After this, add the remaining rubble so that it surrounds the drainage pipe entering the pit. The rubble mixture should sit around 5-inches from the surface.

Then, add the heavy-duty landscaping fabric across the stone. This provides effective drainage while preventing soil and gravel from entering the main section of the soakaway.

Finish by adding some topsoil to the soakaway so that the ground is level, and then reapply the turf.

Related: Best Compost to buy

Building a Soakaway Using Soakaway Crates

What is a soakaway crate?

Given the popularity of soakaways, there are products designed especially for the drainage system known as soakaway crates. These replace the need for using gravel and rubble and tend to offer even more efficient draining for the soakaway.

Soakaway crates look very much like empty milk crates, although they have much more structural integrity. They come flat-packed and easily pop into shape, after which they are placed into the soakaway pit rather than rubble infill.

One of the main advantages of using a soakaway crate is ease of construction. Because you aren’t transporting large amounts of stone materials into the soakaway, the entire process becomes much easier.

The only drawback to using a soakaway crate is the added expense. They are much costlier than using basic stone infill, but the convenience they offer often outweighs the added expense of buying them.

How build a soakaway using soakaway crates

Building a soakaway using crates isn’t much different from using stone infill.

Start by digging the standard 1m x 1m x 1m trench, increasing the size if necessary, espiecally if the crates won’t fit the hole.

One of the main differences of using crates is the need for a membrane material. A robust porous membrane is necessary for covering the excavated walls of the soakaway to ensure that water can pass through into the empty section of the crate without the risk of clogging

Not using a membrane to line the hole sees soil and other sediment materials pass through into the crate, clogging it up and making the soakaway less effective at draining, so always make sure you have a strong protective layer around the soakaway when using crates.

Now, you can insert the crates into the hole. Look for the circular inlet of each crate – this connects to the drainage pipe.

Once connected to the pipe and in position, add a new layer of membrane to the exterior of the soakaway crates. You want the entire surface area to be covered here, so make sure not to miss any parts out or it may cause issues down the line.

Also, with your spare membrane material, cover the drainage pipe in a similar fashion to the soakaway crate. This has a similar effect, preventing any soil from inadvertently passing from the pipe into the crate.

There will likely be some excess areas surrounding the crates in the hole. Simply fill this out with soil or gravel, then add a final layer of topsoil over the top of the soakaway. Roll the turf back on if applicable, use a garden hose and adding new grass seeds should there be some patches.

Things to Remember When Building a Soakaway

  • Never drain sewage water into a soakaway. While sewage water is something you want to address, draining it into a soakaway will only cause it to clog up in the future, meaning you will need to excavate the soakaway to address the problem. Plus, sewage water is terrible for garden soil.
  • Never build a soakaway in clay soil. It’s never going to be effective, as a soakaway requires soft soil to slowly drain into the earth. Making a soakaway in clay soil may cause more waterlogging on the surface of a lawn.
  • A soakaway crate reduces the effort needed to build the soakaway but will probably increase the overall cost of the project. In many cases, it’s about determining what is more valuable, your time or money.

Some tools that will help with the job include:



Popup Gazebo (if it is raining)

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