In short
Comfortable outdoor decking steps rise about 150 to 180 mm each, with treads at least 280 mm deep and ideally wider than the door they lead from. Divide the total drop by your chosen rise to get the number of steps, keep every step the same height, and add a handrail once there are more than two or three.
On this page
Steps are the part of a deck people use most and think about least. A deck that is a pleasure to sit on can still be a nuisance if the steps down to the lawn are steep, uneven or slippery. On a sloping garden there may be several flights, so getting the sizes right matters even more.
The two numbers that matter
Every step has a rise (how much higher it is than the one below) and a going or tread (how deep it is front to back). Indoors, stairs can be fairly steep because they are short of space. Outdoors there is usually room to be generous, and generous steps are safer when they are wet.
| Measurement | Comfortable outdoors | Avoid |
|---|---|---|
| Rise per step | 150 to 180 mm | Over 200 mm |
| Tread depth | 280 to 400 mm | Under 250 mm |
| Width | At least the door width, ideally 1 m or more | Under 800 mm |
The single most important rule is that every rise in a flight is the same. People set their stride on the first two steps. A step that is 20 mm higher or lower than the others is the one people trip on.
A useful check is that two rises plus one tread should come to roughly 550 to 700 mm. That is the range most people’s natural stride falls into. A 170 mm rise with a 300 mm tread gives 640 mm, which feels right.
How many steps do you need?
Measure the drop from the top of the deck boards to the ground where the bottom step will land. Then divide by the rise you want, and round to a whole number.
For a drop of 520 mm:
- 520 ÷ 170 = 3.06, so three steps.
- 520 ÷ 3 = 173 mm per rise.
Remember the deck itself counts as the top. Three rises means two treads plus the deck surface. On a slope, the ground at the bottom may be lower than it looks, so measure where the last step will actually sit, not at the edge of the deck.
Box steps or stringers?
There are two common ways to build decking steps.
Box steps
Each step is a small, boarded frame stacked on the one below, like a staircase of open boxes. They suit short flights of one to three steps, look solid, and can run the full width of the deck. A long box step across the whole front of a deck doubles as extra seating, which is why it is popular on family decks.
Stringers
For taller drops, the treads sit on notched side beams called stringers, fixed to the deck frame at the top and a footing at the bottom. They use less material for a long flight and leave the space underneath open. On a raised deck on a sloping garden, stringer steps with a handrail on each side are usually the neater answer.
Handrails and edges
Government guidance on guarding (Approved Document K) is written for buildings, but it is the benchmark most installers use outside too. In practice:
- Add a handrail once a flight has more than two or three steps, or as soon as anyone in the house is unsteady on their feet.
- Where a deck or landing is more than 600 mm off the ground, guard the open edge with a balustrade.
- Keep gaps in a balustrade small enough that a 100 mm sphere cannot pass through, so small children cannot squeeze between the spindles.
On composite decks, matching composite or aluminium rails are common. Glass is popular where the view matters, though it costs more per metre.
Making steps safe when they are wet
Most falls on decking steps happen in autumn and winter, when the boards are damp and covered in leaves. A few details help a lot:
- Grip on the nosing. The front edge of each tread takes the most wear and is where the foot lands. Composite boards with a textured surface, or a contrasting nosing strip, give a better grip.
- Contrast. A slightly different colour on the front edge of each tread makes the edges easy to see in poor light, which helps older eyes.
- Lighting. Small lights set into the risers or the side of each step cost little and mean the steps can be used after dark.
- Shade. Steps on the north side of a deck stay damp longest. Keep them swept and give them a wash with warm soapy water in spring and autumn.
Wide steps as part of the design
Steps do not have to be a narrow flight tucked in a corner. On a gently sloping garden, a deck with two or three very wide steps running its full length becomes a set of low terraces, with somewhere to sit, put pots and watch children on the lawn. It also spreads people out, so nobody is queuing on a narrow stair with a plate of food.
On a steep garden, the opposite is often better: one compact flight with a landing halfway, so nobody is facing a long run of steps straight down the hill.
Planning and steps
Steps on their own rarely trigger a planning application. What matters is the height of the deck they serve. If any part of the platform is more than 30 cm above the ground, it is no longer permitted development and normally needs planning permission. That is common on sloping gardens, where the deck carries the level out from the back door.
Our page on decking on a slope goes through the layouts and heights in more detail.
What decking steps cost
Fitted, a composite step typically costs £80 to £200 per step, depending on width, whether it is a box step or on stringers, and whether the boards are hollow or solid. Rails add roughly £40 to £120 per metre, and glass from £200 to £500 per metre. Small step lights are usually £30 to £100 each, fitted.
Across a typical sloping garden, steps and the handrail often add £800 to £2,000 to the price of the deck. Our composite decking cost calculator lets you add steps and a balustrade to see the effect.
If you are planning steps as part of a new deck, we can put you in touch with a local installer for composite decking Bradford homeowners trust with the awkward slopes.
Quick checklist
- Same rise on every step, 150 to 180 mm.
- Treads at least 280 mm deep.
- At least as wide as the door, ideally a metre or more.
- Handrail on longer flights; balustrade on edges over 600 mm.
- Textured or contrasting nosings, and a light on each step if you use the garden after dark.