How to Level a Sloping Garden
Few gardens have a perfect lawn. Whether it is a few bumps and lumps or an irregular shape, most of us have a few minor issues when it comes to our lawn. Many are not much a problem and something you can easily work around, yet there is one type of issue that can be much more problematic if left untreated and it is one of the asked lawn care and gardening questions – how to level a sloping garden.
While a gentle slope is nothing to worry about – it can actually promote good soil drainage – anything too steep does make it harder to do various things, from mowing the lawn to having a nice play area for your kids.
Thankfully, it is possible to level a sloping garden by yourself, although you may want to ask some friends or family for assistance as the task is quite labour-intensive. That said, there are some people that will find it is better to hire a professional landscaper to level their garden, especially in large spaces with steep slopes.
This guide covers everything you need to know to level a slope in a garden, from planning and preparation to the tools and materials needed for the job.
Table of Contents
Why Level a Sloping Garden?
Before we start, let’s look at a few reasons as to why you may want to level a slope. The most obvious is that a slope limits the amount of free space and activities you can do on the lawn, such as somewhere for kids to play, mowing the grass, or relaxing in a lounger.
Another big reason to level the garden is that too much of a slope may lead to drainage issues, potentially flooding areas in the garden or near your house. Soil erosion is another big issue caused by slopes, making the area more difficult to plant in.
Plus, when using a retaining wall to level the slope, you create an attractive fixture in the garden, especially when adding new plants and flowers behind the wall.
Tools and Materials That You Will Need
Despite this task requiring a lot of planning and being labour intensive, you don’t need too many tools or materials. Here’s a rundown of everything you need:
- Two stakes and string to measure the rise and run
- Spirit level to make everything is level
- Shovel for digging – the more people working the more shovels you need
- Soil compactor – you may need to hire this
- Grass seed/new turf for the new area
- Materials for a retaining wall (more below)
Materials for Building a Retaining Wall
A retaining wall is necessary for supporting the land after you level it out, holding back the soil and moisture from the raised section you create. The wall can be made from a few different materials, although stone or sleepers are usually the most popular.
Various stone materials are available for this, including concrete stacking blocks, natural stone, and reclaimed house bricks. Some are cheaper than others, so consdier your budget before choosing one.
Railway sleepers are large pieces of wood that are perfect for creating a retaining wall. They are cheaper than stones when buying reclaimed sleepers, while new sleepers are more expensive. In any case, the large length and width make them great for stacking, often being easier to install compared to stone blocks.
An increasingly popular option for retaining wall materials are stone gabions. These are essentially large wire cages that are filled with stones. They are more affordable than stone blocks and look great too, while offering the same stability as other materials.
Preparing the Garden
As with any major landscaping project, properly preparing the garden makes the entire process much easier and safer.
Here are some important steps to take when prepping the garden:
Inspect the Area
Take the time to carefully inspect the slope before you start anything. This should give an idea of how dry the soil is, how steep of a slope you are working with, and whether there are possible obstacles under the ground like pipes or wiring.
Get Planning Permission
Contact your local authorities to determine whether planning permission is required for the project. While most homeowners should be fine, there are instances where restrictions limit how much you can do without permission from a local authority.
This is also important for identifying whether there are any pipes or wiring in the ground that you could disturb when digging.
Water the Ground if Needed
You will be doing a lot of digging here so you want to make sure the soil is moist enough. Digging lots of dry soil is backbreaking work, so give it a good water at least 24 hours before you start digging, especially if its not rained in a while.
Be careful not to overwater though – too much moisture can be just as difficult to dig and move!
Choose the Right Time to Start
When working out how to level a garden this one is often overlooked – pick the right time to level your garden! Never do this project in winter as it will make some steps incredibly difficult, with spring being the best time of the year to start the project.
Spring is a good option because you want to incarnate a new lawn as quickly as possible to ensure the soil remains compact and the grass seeds will grow quickly at this time, while it is likely the soil is wet enough from rain.
How to Measure the Rise and Run of a sloping garden
- The first step you need to take is measure the rise and run of the slope. The run is where the newly levelled lawn is going, and the rise is the position of the retaining wall that will support the raised area you create when levelling.
- To measure this, you need two stakes, string, and a spirit level.
- The first stake is placed at the top of the slope, with the second going into the ground at the bottom of the slope. Make sure both stakes are in line with each other.
- Tie one end of the string to the first stake at ground level. Tie the other end to the second stake at the bottom of the slope – tie it to the part of the stake that leaves the string level, usually near the top of the stake.
- The string between the stakes is called the ‘run’ and the height of the string on the second stake is called the ‘rise’.
- Place the spirit level on the string to ensure it is level. The run is the area where the new lawn is going to go, so you want it as level as possible.
- Measure the height of the rise now, which will be the height of your new retaining wall. Never make the wall taller than 70cm, as this is too high for a retaining wall, with the pressure of the soil and moisture making it too unstable.
This is one of the most labour-intensive parts of the levelling process. If you are creating a raised flat surface where the slope was, then you just need to dig away the surface area of the slope to make it easier to add new top soil to level things out.
If lowering, you need to remove a lot more soil and shift it down to the newly flattened area. A wheelbarrow may be a good idea for this, especially when levelling down a large area. Keep the soil though as you will use this to fill behind the retaining wall you are about to build.
Building the Retaining Wall
The raise you measured is the starting point of the retaining wall. It should be no higher than 70cm, running across the length of the bottom of the slope. The gap behind this wall will be filled with soil to create flat raised surface for a new lawn.
You can also incorporate plants and flowers around the border of the retaining wall, which is a good idea as the root systems help with soil compaction, minimising drainage issues and the risk of the wall collapsing. Plus, it will look fantastic!
To build the retaining wall, simply stack the desired materials along the length of the slope, building several levels to the required height – remember not to go higher than 70cm!
You can create different aesthetics for the retaining wall and your garden depending on the material used, so consdier what look you want to achieve. Also, the price can vary, so if you are on a tight budget consider a cheaper material liker reclaimed railway sleepers.
Fill in the Area Behind the Wall with Soil
Once the retaining wall is built, you can start to fill in the area behind it with new soil. This soil is going to become your new level lawn, which is why is we took the time to measure a level run when placing the stakes.
Do not rush this part as you want to ensure that everything is level for your new lawn. Take the time to carefully fill in with soil, slowly raising the level until you have a flat surface where the slope previously was.
When creating a raised area, you can just order some good quality top soil and use this to level things out. This is also great for encouraging a healthy new lawn, with the top soil providing ample nutrients for the grass seeds or new turf.
If lowering part of a current lawn, just use some of the excessive soil you dug away to fill in the gap.
Check that the New Lawn is Level
Now that you have filled the space between the land at the top of the retaining wall with soil, it is time to check that the newly levelled area is in fact level!
You can estimate this just by looking but seeing as you already used a spirit level you may as well use it here too. Take the spirit level and measure across the surface of the newly flattened lawn, checking for any slight sloping and filling /removing soil as needed.
Another way to determine this is by using the stakes and string. Place a stake at every corner on the new lawn, running string between each one at the same height. If the string runs level, the lawn should be level too.
This is a good time to add compost if you have any, with the added nutrients encouraging healthy growth of the new lawn and any plants you are adding to the borders.
Compact the Soil
Once the soil is level, it is time to compact it all. This removes any lingering oxygen and small cavities that develop when adding the new soil. By doing this, you avoid any lumps or bumps developing on the new lawn, so it is worth taking the time to compact all the soil.
If not, the next time it starts to rain there is a good chance the lawn becomes uneven again due to random lumps and bumps. This is the last thing you want given all the effort you are making to level the slope.
To properly do this you need a soil compactor. This is a type of gardening equipment that operates similarly to a lawn mower. You don’t need to buy this for a one-off job, instead hire it from a local company – you can easily rent a good soil compactor for a day or two without spending much.
Just move the soil compactor across the surface area of the lawn, going over it a few times to remove all oxygen and holes.
Establish a New Lawn
You should have a nice flat surface area where your slope used to be, so it is now time to establish a new lawn! Simply add grass seeds or turn to the top of the soil, following the appropriate instructions depending on what method you use.
Seeding requires you to toss the seeds across the surface and adding a small amount of topsoil. For a turn, you need to lay them down flat on the soil, placing closely together to avoid unsightly gaps. If seeding, take the compactor over the topsoil one final time to encourage better root systems and a healthier lawn.