Garden Steps & Sloping Gardens

A sloping garden is both a design challenge and an opportunity. Steps cut into a slope give structure, make the space navigable, and, done well, become a genuine landscape feature. Done badly, they become a trip hazard and a drainage problem. Getting the dimensions right and choosing appropriate materials for a UK climate are the two most important decisions you’ll make.

Step Proportions: The Rule of 26

Outdoor steps have different ergonomic rules to indoor stairs. A widely used rule of thumb for outdoor steps is:

2 × riser height + tread depth = 650–700 mm

For a comfortable outdoor pace:

• Riser height: 150–180 mm (lower is more comfortable and safer for older users)
• Tread depth: 300–450 mm (deeper treads feel more generous outdoors)

A common combination: 150 mm riser, 380 mm tread = 680 mm. Very shallow or very tall risers are uncomfortable and easy to misjudge. Garden steps are not controlled by the Building Regulations, but Approved Document M gives a useful benchmark. Where a new home’s approach has to be stepped, it asks for uniform steps with a rise of 75–150 mm and a going of at least 280 mm.¹ For an additional external stepped route to an accessible home, it allows a rise of 150–170 mm and a going of 280–425 mm.¹

Always pitch the tread very slightly forward (1–2%) to shed rainwater, UK weather means standing water on a flat step quickly becomes an algae-covered slip hazard.

Materials Comparison

Note: all costs above are materials only, per step. Professional installation adds significantly, see cost section below.

Drainage: Often Overlooked

Sloping gardens concentrate water. Steps must not create a dam across a natural runoff path. Key principles:

• French drain at the base of a slope: before installing any steps, understand where water flows after heavy rain. A perforated land drain pipe (commonly 100 mm) in a gravel-filled trench running across the foot of the slope, discharging to a soakaway or a surface water drain, prevents waterlogging at step foundations.
• Don’t seal the sides of steps: leave a gravel joint between step edges and retaining walls so water can escape sideways.
• Sub-base drainage: all steps should be built on a well-compacted sub-base of at least 100–150 mm of Type 1 MOT hardcore topped with sharp sand. Skipping this leads to settlement and rocking treads within a few years, especially in clay soils.

How to Build Concrete Block and Slab Steps

This is the most common DIY garden step build:

You’ll need:

• 100 mm solid concrete blocks (or engineering bricks) for risers
• Concrete paving slabs for treads, chosen or cut to suit your tread depth (commonly 35–50 mm thick)
• Type 1 MOT hardcore
• Sharp sand
• Ready-mix concrete (or bagged ballast + cement for small quantities)
• Spirit level, rubber mallet, safety goggles

Steps:

1. Excavate the slope to form a series of level platforms. Each platform should be the riser height deep and tread depth wide.
2. Compact each level with a plate compactor (hire: ~£50/day) and lay 150 mm of Type 1 hardcore, then 50 mm sharp sand.
3. Set the first riser in a bed of mortar (1:4 cement:sand). Check it’s level and plumb. Allow 24 hours to go off before loading.
4. Lay the tread on a mortar bed over the compacted sub-base behind the riser. Check it’s level side to side and pitched forward 1–2%.
5. Build the second riser directly behind the rear edge of the first tread, repeat.
6. Grout all joints once the mortar has set, using an exterior jointing compound or a well-compacted mortar; weak or poorly filled joints crack and wash out in frost.
7. Seal natural stone or sandstone slabs with a breathable stone sealer to prevent staining and algae growth.

Railway Sleeper Steps

Untreated softwood rots quickly in ground contact. For steps that will last, specify hardwood sleepers (oak or reclaimed hardwood) or softwood sleepers pressure-treated to Use Class 4, the treatment level for timber in ground contact.³ Fix with 600–900 mm rebar stakes driven through pre-drilled holes into the ground. Gravel or compacted hoggin behind each sleeper provides both drainage and stability.

Retaining Walls and Terracing

For slopes steeper than 1:3, you’ll likely want to terrace the garden with retaining walls rather than a pure stair run. Retaining walls over 600 mm high that support soil (especially near property boundaries, roads, or structures) should be designed by a structural engineer. Planning law counts engineering operations as development, so large-scale re-grading or terracing of a slope can need planning permission even where the walls themselves fall within permitted development limits (see below).⁴

Common retaining wall options:

• Concrete block wall with rebar and concrete fill: most robust, £200–£400 per linear metre installed
• Timber sleeper walls (horizontal): good look, £150–£300 per metre, 15–25 year life
• Gabion baskets (stone-filled wire mesh): excellent drainage, £180–£350 per metre, very long life
• Dry-stone wall: traditional, suits rural and period settings, requires a skilled craftsperson, £300–£600+ per metre

Planning Permission

In England, most garden steps and retaining walls are covered by Permitted Development rights and don’t need planning permission, provided:

• Any new hard surface of more than 5 m² between the front of the house and a road is porous, or drains to a lawn or border within the garden⁵
• Retaining walls do not exceed 1 m in height next to a highway used by vehicular traffic (including the footway of such a highway), or 2 m elsewhere⁶
• The property is not a listed building: the wall allowance does not apply within the curtilage of a listed building⁶

In a conservation area, also check with the council whether an Article 4 direction removes these rights.

If in any doubt, ask your local planning authority for pre-application advice before you build. Councils may charge for it, though government guidance encourages them to offer a basic level of service free.⁷

Professional Installation Costs

Labour rates for landscapers and groundworkers range from £200–£350 per day in 2026. Get at least three quotes, for example from members of BALI (the British Association of Landscape Industries).

Safety and Anti-Slip

UK weather makes outdoor steps inherently slippery in winter. To reduce risk:

• Choose textured, riven or sawn-finish surfaces over polished.
• Add anti-slip strips (aluminium-edged stainless inserts or grip tape) to the nosing of each tread.
• Maintain steps annually: brush off algae and moss with a stiff brush, and where a chemical treatment is needed use a proprietary path and patio treatment authorised for moss and algae control rather than household bleach or a diluted hypochlorite mix, then re-seal natural stone.
• For steps used by elderly household members, a stainless steel handrail fixed into the slope alongside the steps can be life-changing, budget £200–£500 for a simple handrail set into concrete footings.