How to Build Garden Steps in the UK

Garden steps are one of the most useful improvements you can make to a sloping plot. A well-built flight connects levels that would otherwise feel awkward and separate, makes every part of the garden properly accessible, and gives a sense of intention to ground that might otherwise feel like a problem to be managed. The process is well within reach for a confident DIYer. The challenge is not the complexity of the build – it is the accuracy of the calculation and the quality of the base. Get those two things right and the rest follows.

This guide covers three practical approaches suited to UK gardens: railway sleeper steps, pressure-treated timber riser steps with compacted gravel or crushed stone treads, and brick or block riser steps with paving slab treads. The base preparation method, rise and tread calculation, and drainage principles apply to all three. Where the build technique differs, each is covered in full in the build section.

What you’ll need

Choosing your material

The material you choose defines the character of the steps and determines how much groundwork is needed. Railway sleepers – new hardwood or softwood, not old creosoted track sleepers – are the most forgiving first-time build. The weight and size of each sleeper means it stays in place on a compacted base without mortar or complex fixings, and the natural look suits most garden styles. Pressure-treated timber risers with compacted gravel or crushed stone treads are faster to build and give a clean result, but the gravel surface needs occasional top-up as material migrates underfoot. Brick or block risers with paving slab treads are the most permanent and formal option, requiring mortar and a concrete strip foundation at the base, but will outlast everything else on the list.

One material note worth emphasising: avoid old railway sleepers treated with creosote for any build where you will be touching the timber or have children or pets using the area. Creosote-treated timber is classified as hazardous waste in the UK and is no longer sold for garden use. New hardwood or softwood sleepers – untreated or pressure-treated – are the correct choice and are widely available from timber merchants and garden centres.

Calculating rise, tread and width

The rise is the vertical height of each step; the tread (also called the going) is the horizontal depth you step onto. These two dimensions need to work together. The standard formula for comfortable outdoor steps is 2R + G = 550-700mm (two times the rise, plus the going or tread depth). So a 150mm rise needs a going of at least 250mm to hit the minimum 550mm total, but 350-400mm feels far more comfortable and is the practical target for a garden. A 170mm rise works well with a 300mm tread (2×170 + 300 = 640mm – comfortably within range).

Building Regulations Part M sets the external step rise at 150-170mm and tread at a minimum of 280mm. These are the legal minimums for steps forming part of a structure. For garden steps with no structural requirement, you have more flexibility, but the comfort range sits in exactly the same zone: a 150mm rise with a 350-400mm tread is near-ideal for most garden settings and suits a relaxed climbing pace. A rise over 200mm starts to feel steep outdoors where there is typically no handrail to assist. Anything under 100mm feels more like a trip hazard than a step.

To work out how many steps you need, measure the total vertical height of the slope in millimetres and divide by your chosen rise. A 900mm slope with a 150mm rise needs 6 steps exactly. The total horizontal space the flight will occupy equals the number of steps multiplied by the tread depth – 6 steps at 380mm tread needs 2,280mm of run. If the slope is steeper than the available horizontal space allows, you have two options: reduce the tread depth (accepting a slightly less comfortable step), or introduce a landing platform partway up. A landing breaks a long flight into two shorter ones, gives a place to rest, and adds visual interest to the garden.

Building the steps

The build process below covers the full method for all three material types. Base preparation is identical for all. The riser installation differs by material from step 3 onward.

Step 1 – Mark out. Use canes and string to mark the position of every step across the slope before lifting a spade. Confirm each spacing matches your calculated tread depth. Run a string line from the base of the slope to the top to keep the flight straight. Measure the total width of the flight and peg both sides. This marking-out stage takes twenty minutes and prevents the most common error: excavating the wrong depth or starting the flight in the wrong place.

Step 2 – Excavate. Start at the bottom step and work up the slope. For each step, cut back into the slope to create a flat horizontal platform. The depth of that platform needs to accommodate 100mm of compacted MOT Type 1 sub-base plus the thickness of your riser material (typically 75-100mm for a sleeper or masonry riser). Remove all organic material – topsoil, roots and loose material – from the excavated face. Compact the exposed sub-soil firmly before laying any fill. Spoil from the excavation is useful fill material for the upper steps.

Step 3 – Lay and compact the sub-base. Pour 100mm of MOT Type 1 into each excavated step platform. Spread it evenly with a rake and compact with a plate compactor or hand tamper. This is the most important single step in the build. Steps built directly on uncompacted soil or topsoil will settle unevenly within one or two winters, producing trip hazards and a visually ragged result. A properly compacted 100mm MOT Type 1 sub-base prevents that movement. Lay and compact each step’s base before moving to the next one up – do not excavate the whole flight before starting the compaction.

Step 4 – Set the risers and treads.

For sleeper steps: place the first sleeper on the compacted base with its front face at the front of the excavated step. Check it is level side to side using a spirit level. Drive two 600mm timber stakes into the ground hard against the back face of the sleeper – these prevent the sleeper rolling forward under repeated foot traffic. Fix the stakes to the sleeper with two 150mm coach screws per stake, pre-drilling to avoid splitting. Fill behind the sleeper with compacted MOT Type 1 to within 20-30mm of the top of the sleeper, then top with angular decorative gravel or stone chippings raked level and pitched very slightly forward. Place the next sleeper on top of the compacted fill, repeating the process up the slope.

For timber riser steps: set a length of 100x50mm or 150x50mm pressure-treated timber across the base of each step as the riser. Fix it in place with 600mm steel rebar pins driven vertically through pre-drilled holes in the timber into the ground – use three pins per riser for stability. Fill behind with compacted MOT Type 1, then top with compacted angular gravel or crushed stone. Gravel steps need containment at the sides – either the natural slope of the excavation or treated timber edging boards to prevent the fill migrating sideways.

For brick or block riser steps: lay a 100mm wide concrete strip footing at the base of each riser position before any masonry work begins. Mix concrete at a 1:2:3 ratio (one part cement, two parts sharp sand, three parts coarse aggregate) and allow it to cure for at least 24 hours before laying brickwork on top. Bed bricks or blocks in a standard 4:1 sharp sand and cement mortar. Once the risers are set and mortar has cured (allow 24-48 hours), bed paving slab treads on a 50mm mortar bed, checking each slab is level side to side and pitched forward for drainage.

Finishing, safety and drainage

Drainage is the detail that separates steps that last from steps that become a slip hazard within a season. Every tread must have a slight forward pitch from back to front. For paving slab treads, a fall of approximately 1:60 to 1:80 is the recommended minimum – that is roughly 5-8mm of fall across a 400mm tread. This is barely visible to the eye but prevents water pooling on the surface. Pooled water freezes in winter and creates a serious slip risk, particularly on stone and concrete surfaces that develop algae growth in shaded or north-facing positions.

Anti-slip treatment adds a useful second layer of protection. For timber treads, a grip-strip applied across the front of each tread is the most effective option – it wears well and is easily replaced. For stone and paving slab treads, a purpose-made patio anti-slip treatment applied each spring significantly reduces algae build-up before it establishes. A pressure wash in early spring, followed by treatment, is far easier than attempting to clear an established algae bloom from textured stone. For heavily shaded steps that stay permanently damp, wire mesh panels cut to fit the tread and fixed with masonry pins provide traction even when the surface is wet.

A handrail is not a legal requirement for garden steps but is worth fitting for any flight of more than five steps, or where the steps will be used regularly by older visitors or children. The most practical garden handrail is a galvanised steel post set in concrete on each side of the flight, connected with a timber or steel rail. Posts should be set at least 600mm deep in a concrete footing. For sleeper steps, fixing a treated timber rail directly to the top of the sleeper risers using galvanised brackets is a neater alternative that suits the aesthetic of the build.

The final step at the top of the flight should land flush with or very slightly below the upper garden level – a step that rises above the surrounding surface creates a trip hazard at the top of the flight. Similarly, the bottom step should sit flush with the path or lawn below. If the bottom step is raised above the adjacent surface, it tends to collect mud and debris against its face and looks visually awkward.

Common mistakes to avoid