Decking steps

What size should decking steps be?

Approved Document K (England) sets limits for private stairs in Table 1.1:

External tapered steps that form part of a dwelling should have a going of at least 280 mm. The document applies to stairs forming part of a building, so ask Building Control whether your garden deck counts.

How do you work out the steps?

1. Measure from the ground to the top of the deck.
2. Divide by a rise inside the limits to get the number of steps, rounding up.
3. Divide the height by that number for the actual rise.
4. Choose a going so that 2R + G lands between 550 and 700 mm.

A 600 mm deck needs four rises of 150 mm. A 250 mm going gives 2R + G = 550 mm, inside the range. A 450 mm deck with three rises of 150 mm and the same going works too. All steps in a flight should match.

How do you build the steps?

As a separate structure fixed to the deck. An installer building on an uneven slab made steps as modular boxes and locked them to the frame and footing with brackets, which suits a deck that has to take regular foot traffic. Another builder adds extra bracing where people leave the door, since a bouncy deck shows most there. Millboard’s guide asks for 300 mm joist centres on steps, closer than the 400 mm for the deck, and Eurocell warns that its step edging only matches the grooved side of its board.

Do steps need a handrail?

Where the drop is more than 600 mm, guarding is expected, and guarding on stairs is 900 mm high in Approved Document K. See balustrades for the numbers.

What do steps cost?

BestBuilders prices steps at £80 to £200 each in its 2026 guide, with no VAT status. Add them to the total in the decking calculator.

How do you make deck steps and stairs, and what is the rule?

Approved Document K (2013, England) gives a private stair a rise of 150 to 220 mm, a going of 220 to 300 mm, a maximum pitch of 42 degrees, and 2 times rise plus going between 550 and 700 mm. It allows open risers in a dwelling only if the treads overlap by at least 16 mm and a 100 mm sphere can’t pass through. Older sources conflict with those numbers: a 2011 British Woodworking Federation page shows an earlier table. Use the gov.uk text, and check which edition is in force where you build.

How builders construct them:

• Wickes’ raised-deck guide keeps step supports, which it calls stringers, no more than 450 mm apart on solid level ground, fixes the vertical riser first, then screws the tread through the second groove into the riser below.
• Ultra Decking builds steps as stacked C24 timber boxes, with the height equal to the rise and the depth equal to the tread. It divides the total rise by a target rise, for example 180 mm, so every step is identical.
• TDCA’s raised-deck code: a single run up to 2.4 m high with no more than 14 treads, a going of at least 250 mm, openings under 100 mm, solid stringers and a concrete pad at the foot.

The TDCA figures apply to raised decks on new homes. See balustrades for handrails.