Three ways to deal with a slope
Cut into the slope
Where the garden rises away from the house, we dig into the bank to create a level area and hold the cut face with a retaining wall. This keeps the patio low and close to the house's floor level, and it never counts as a raised platform. The downside is the volume of soil to remove, which on a garden with no side access means a lot of barrowing.
Build up with fill
Where the garden falls away from the house, the patio can be built up to meet the back door level, held at its outer edge by a retaining wall. The fill must be compacted in layers; loose soil under a patio settles for years. This is where the 30cm rule matters most (see below).
Cut and fill with split levels
Most sloping gardens end up with a mix: a level terrace by the house, steps, and a second patio or lawn at a different level. Splitting the height between levels keeps each wall low, reduces the soil that has to be moved and creates natural places for planting and seating.
The 30cm rule
Under national permitted development rules, a raised platform, including a raised patio, is only allowed without planning permission if it is no more than 30cm above the ground. The Planning Portal measures this from ground level, so on a slope the highest point is usually the outer edge, furthest from the house. Platforms must also not cover more than half the garden together with extensions and outbuildings.
The Planning Portal adds that significant embanking or terracing to support a hard surface might need permission. If your plan involves building up a lot of ground, check with Stockton-on-Tees Borough Council first.
Designing in two levels, or cutting in rather than building up, usually keeps a sloping-garden patio within the rules.
Retaining walls
A retaining wall holds back soil, and soil is heavy, especially Stockton's clay when it is wet. The British Geological Survey shows glacial till under much of Eaglescliffe, Elm Tree and Fairfield; till swells and pushes harder when saturated. A garden wall built only to look good can lean or crack within a few winters if it is asked to hold back a bank.
What a sound retaining wall needs:
- A proper footing, wider than the wall and on firm ground.
- Drainage behind it: free-draining stone backfill and a perforated pipe or weep holes through the wall, so water does not build up behind.
- The right construction for the height: low walls in brick or block with a concrete footing; taller walls may need reinforcement and an engineer's design.
- A coping to shed water and finish the top.
Walls along a boundary have height limits under permitted development: one metre next to a road and two metres elsewhere. Work on or near a shared boundary wall can also bring in the Party Wall etc. Act, and GOV.UK explains when you must tell your neighbours. Our garden walls page has more detail.
Steps
Steps make or break a sloping-garden patio. We aim for:
- Even risers throughout a flight, so nobody trips on an odd step.
- Treads deep enough for a whole foot, and slightly falling so water runs off.
- Good grip, which means textured slabs or nosings, and keeping them clean. Algae on steps is the main winter hazard.
- Width that suits the garden: generous steps feel like part of the patio rather than a ladder.
Our garden paths and steps page shows the options.
Water on a slope
A slope sends water downhill, onto your patio if it is at the bottom and off it if it is at the top.
- Patio below a bank: run a drain along the foot of the retaining wall to catch water seeping out of the slope, as well as the usual fall away from the house.
- Patio above the garden: make sure run-off does not pour over the edge onto a neighbour's land or wash out the lawn below.
- Next to the house: the patio must still finish at least 150mm below the damp-proof course, which Approved Document C expects above adjoining paving. Where the garden rises towards the house, that often means cutting the ground down and adding a drain along the wall.
Our patio drainage guide covers falls, channels and soakaways in more detail.
Things to check before work starts
- Levels: we survey the fall across the garden, the floor level at the doors, the damp-proof course and air bricks.
- Access: how soil and stone will get in and out.
- Services: drains, manholes and cables crossing the garden.
- Boundaries: who owns which walls and fences, and whether the neighbours need to be told.
- Planning: the 30cm rule, embanking, and any conservation area or listed building issues. See our conservation areas guide.
Questions people ask
Can I build a patio on a slope in the UK?
Yes. Cut into the slope, build up with a retaining wall, or split the patio into levels. Keep raised parts within 30cm of the ground to stay inside permitted development.
Do I need planning permission for a raised patio?
If any part is more than 30cm above the ground, yes. Significant embanking or terracing may also need permission.
How high can a garden retaining wall be?
Planning limits on boundary walls are one metre next to a road and two metres elsewhere. Structurally, taller retaining walls need more substantial design, and high ones should be designed by an engineer.
Is it cheaper to cut into a slope or build up?
It depends on the garden. Cutting in means removing soil; building up means bringing in fill and a stronger wall. Splitting the height between levels is often the most economical.
Sources: Planning Portal: decking and raised platforms; Planning Portal: patios and driveways; Planning Portal: fences, gates and garden walls; GOV.UK: party walls and building work; GOV.UK: Approved Document C, resistance to moisture; BGS Geology Viewer.