How to level a sloping garden

Inspired by a helpful YouTube guide. This walk-through is based on the popular video "How to Level a Sloping Garden", which gives a clear overview of the planning and groundworks involved in creating usable flat areas from a sloped plot. The section on preserving and returning topsoil is the one most people skip — don't.

1. Assess the slope and set your ambition

Before anything else, work out how much slope you're actually dealing with. Knock in a peg at the top of the slope and a peg at the bottom. Tie a string line between them and get it level using a spirit level on the string. The vertical distance from the bottom of the lower peg to the string gives you the total drop.

A gentle slope of 20–30cm over 5 metres can be levelled into a single flat area with a modest amount of soil movement. A steep drop of a metre or more over the same distance is better addressed as terracing — two or three level sections separated by low retaining walls or planted banks.

2. Plan for drainage

Level gardens are lovely. Level gardens that pool water every time it rains are not. Before you start moving any soil, think about where the water is currently going and where it'll go once the slope is gone.

Often a gentle fall of 1 in 80 (about 1.25cm per metre) away from the house is enough to prevent pooling. If the site is already prone to waterlogging, you may need a drainage channel or soakaway at the lowest point. Get this sorted in your plan rather than discovering the problem once everything is flat and turfed.

3. Strip and stack the topsoil

Topsoil is the layer of darker, organic-rich soil at the surface — usually the top 15–30cm. It's valuable and you need it back on top once the reshaping is done. Strip it off the entire area using a spade or mini-digger, stack it to one side in a heap, and cover it with a tarpaulin to keep the rain off.

Never bury topsoil under subsoil — it goes anaerobic and effectively becomes useless. Keep the layers separate throughout the job.

4. Mark out the level using pegs and a string line

Using the string-line method from step 1, set up a grid of pegs across the whole area at roughly one-metre intervals. Get each peg to the finished level you want — this is your target height and your guide throughout the earthmoving.

A laser level makes this significantly faster if you can borrow or hire one. A long spirit level and a straight piece of timber will do the same job more slowly but just as accurately.

5. Move the subsoil — cut and fill

The principle is simple: the soil you cut from the high end goes to fill the low end. This is called cut-and-fill. Where the finished level is below the existing ground, you dig down. Where it's above, you build up with the material you dug out.

Work in stages across the plot, checking against the peg grid as you go. For large areas, a mini-digger hired for a day is genuinely transformative compared to doing it by hand. For a garden the size of an average Kent back garden, two strong people with spades can manage a gentle slope in a long weekend.

6. Compact the subsoil layers

Any fill material — subsoil you've moved into a lower area — needs compacting in layers of no more than 15cm at a time. Use a plate compactor (hire from any tool hire place) or a hand tamper. Skipping compaction leads to settlement over the following months, which means your new lawn develops hollows and your patio rocks.

On the cut sections (where you've dug down), the existing soil is generally already compacted enough. Just remove any loose material.

7. Return and spread the topsoil

Once the subsoil is shaped and compacted, bring back the topsoil and spread it evenly across the whole area to a depth of at least 15cm — 20–25cm is better for a good lawn or planting bed. Rake it level, removing any stones, roots, or debris.

Allow the surface to settle for a week or two before turfing or sowing. A heavy downpour after you've raked it smooth will highlight any remaining hollows, which can be topped up at this stage far more easily than after the grass is down.

8. Turf or seed, and wait

Lay turf or sow seed according to the season — spring and early autumn are the best times for both in the UK. For a levelling job, turf is generally preferable because it establishes faster and holds the soil together while it knits in.

Keep off the new lawn for at least six to eight weeks and water thoroughly in dry spells. The temptation to walk across it is real. Resist it.

When to call a handyman

For a large or steep slope, or anywhere a retaining wall is needed, it's worth getting help. Retaining walls need to be built correctly to handle the soil pressure — a poorly built one can fail and push over, and that's a much bigger job to fix than it was to do right first time. Richard can help with the landscaping, retaining structures, and the garden finishing in Sandwich and the surrounding area.