This article contains affiliate links
Clay soil is well known for its ability to become compacted and form dense clods of earth. These clods can be challenging to break up at any time of the growing season.
During winter the clay can become saturated, sticky and unworkable. However in summer the clay can become rock solid becoming impossible to break up.
Such composition is due to clay soils heavy and dense particles which bind together tightly. Fragmenting clay particles is critical if you want to transform difficult ground into fertile growing spaces, and sound foundations for landscape installations.
Breaking up and levelling clay is necessary for the installation of lawns, patios, flower borders and many other garden projects.
Consequently in this article, I will explain how to break up and level clay soil in your garden. I will explain the best tools to use, the best time of year, clay soil improvement and much more.
Why level clay soil?
There are many reasons why it is advantageous to level clay soil.
Firstly levelled clay soil can help form soil stability, this is especially so if your existing ground is undulating or on a gradient.
As clay sub-soil compacts well, levelled cay can provide the perfect platform for concrete foundations and base aggregates. This can enable the construction of many exciting landscape structures and installation projects.
Probably the most typical reason to level clay soil in a garden is to create a perfectly level lawn.
Although lawns are best laid on humus rich loams these soft soils are not best for levelling.
Large depths of soft topsoil’s can lead to uneven settlement, sinking and displacement. A better option is to level your clay subsoil fist using a skilled excavator operator to form a level base.
A 25-50mm layer of humus rich loamy soil and then be spread and levelled before the lawn is laid. Finally, one of the most important reasons for levelling clay soil is improving drainage.
When there are low spots or ‘bellies’ in clay soil, water accumulates in times of heavy rain.
These low spots become saturated and boggy leading to further compaction and water accumulation. Eventually these muddy hollows ensure your whole garden becomes easily saturated and boggy.
Consequently by making sure clay soil is levelled and flush you can allow rainwater to run off your gardens surface. This will lead to a better looking garden and a well drained outdoor space.
What is the best way to level clay soil?
The best way to level any area of clay soil is to firstly assess you existing levels. Look at your site from multiple levels to try to gauge the lie of the land.
If you have level features surrounding your site such as walls and fences see how the ground slopes around these features. If you want to make clay soil perfectly flush and level you can set up string lines across your area.
Make sure you pull your string line tight so there is no sag in the line. Now chip off or dig down any high spots or mounds in the clays surface.
If you have a large site an excavator machine with a skilled operator can level areas very effectively.
One of the best ways to level clay soil is to dig over the soil in autumn and spread a 50mm layer of sharp sand over the top.
During the winter as moisture within the clay freezes it will break it and fracture the clods.
The sand will slowly seep into the clay and help to break apart the clay particles. Then during a warm spring day the whole surface can be tilled with a tiller.
This will lead to a loose and fluffy clay soil which can then be easily raked and shovelled level.
How do you break up clay soil?
To break up clay soil you will first need to ensure the clay has an intermediate moisture content. If the clay is too wet it will be too sticky to work and become stuck to your tools.
It will also compact even more underfoot as you work. However, if the clay is too dry it will possibly too hard to penetrate with digging or tilling tools.
The clay soil should be ever so slightly damp to touch but not soggy. You will then need to dig over the clay so it forms lumpy, turned over, clods.
At this point it is well worth spreading plenty of sharp sand, grit and organic matter over the clay soil.
When you till the surface these materials will blend with the clay preventing the particles sticking together.
This will help you reach a fluffy and well textured clay loam in the future.
Now use a tiller machine to break up the clay particles and become a loose and workable topsoil.
How to level a lawn with clay soil
Although clay can be challenging to break up and level it can act as a sturdy base under garden lawns.
If you want to create a perfectly level lawn on clay you need to apply a process of cut and fill. This basically means breaking up high areas of clay soil and spreading them into low areas.
This can be done by chipping off the old lawn and identifying high and low spots. If you want your lawn perfectly level you can mark out your levels with pegs.
Using a very long spirit level and a hammer, tap in pegs along your lawns perimeter.
Tap in pegs so the level reaches the pegs at each end and the bubble sits between the lines.
Carry on all the way around the lawn so you have a visual reference to your completed level. It is a great idea to install level edgings or mow strips around the edge of the lawn.
This way you can lay your new turf perfectly level to the top of the installed edgings.
Now break up your high areas of clay and spread them into your low areas.
This will allow for a more stable and level soil to base your new lawn. Your clay can then be tilled, raked level and a loamy topsoil spread to the finished level.
What is the best way to dig clay soil?
To make digging clay as easy as possible try to do it when it is warm and dry. This will reduce the risk of the clay particles sticking to your tools as you work.
During the middle of the summer however, your clay may be too hard to dig effectively. Consequently, dry days during the spring and autumn are best for digging clay.
The best way to dig clay soil is with a long handled spade and working from a clean edge.
If you slice out narrow and consistent clods these will easily break and crumble under a tillers blades.
Try to slice out rectangle sections about 4 inches (100mm) thick, these will easily dislodge using leverage.
The clogs will also be not too heaving so you can work at a consistent pace. The clods of clay can then easily be turned over or loaded into a wheel barrow.
If you only need to dig down a few inches use an iron bar or grafting spade to break up the top surface. This can be achieved by thrusting down into the clay and levering the handle back towards you.
The loosened clay can then be easily be scooped up using a long handled shovel.
How to improve drainage on clay soil
Clay soils have a particular vulnerability when it comes to poor drainage. As clay particles are extremely fine and dense they can soak up moisture like a sponge.
This can lead to water logging and compaction neither of which is ideal for plants, lawns or people. However there are steps you can take to improve drainage on clay soil.
Firstly, you will need to make your clay soil as level as possible with no low spots. Such low areas encourage the accumulation of standing water leading to boggy conditions.
It is best to have more flush and even soil gradients with perhaps a very slight slope to your lowest boundary. This will enable excess water to escape.
Secondly, you should try to work in as much organic matter to the soils surface as possible. This will help to invigorate soil life and create air spaces within the clay.
Such action will not only improve your clay soils fertility, it will also improve its permeability.
Another way to improve drainage on clay soil is to mix in sharp sand or horticultural grit into the surface.
This gritty material mixes with the fine clay particles and prevents them from sticking together.
Grit and sand is best added when the soil is being dug over or tilled so it can easily mix with the clay.
Drainage channels, swales and ditches can also be excavated around the perimeter of your garden. These will help to draw water away from primary areas such as lawns, patios and flower borders.
For a more comprehensive resource on how to improve drainage on clay soil visit our in-depth article here.
Tools for breaking up and levelling clay soil.
If you’re going to break up and level clay soil yourself, I have listed the best tools for the job below.
Garden forks allow you to force into stubborn and compacted clay especially when it's dry.
Spades enable you to neatly slice into clay soil cutting out manageable sections for breaking up later.
Long handled shovel
A good long handled shovel will allow you easily scoop up loose clay which has been broken up during turning and excavation.
A grafting bar is a great tool for thrusting down into thick and compacted clay ground, it can also be used to chip off high areas of compacted, clay soil.
Mattocks and pick axes are excellent tools for loosening clay soil which has become compacted.
Wheelbarrows are very effective at moving around and carting excavated clay soil away from site or into low areas.
Mechanical tillers are perfect for breaking up clay into smaller clod and enabling clay soil to mix with grit and organic matter.
Thank you for reading our article on how to break up and level clay soil. Below I will include some other resources you may also find useful.
'As an Amazon associate I earn from qualifying purchases'