Composite Step Construction

The following instructions on constructing composite decking steps is a guide only, please work in conjunction with Building Regulations (specifically, Part K) if you need to do so.

You may also need to add balustrade, consult with Building Regulations or local planning officer for guidance.

Timber Framed Steps


constructing composite decking steps

You can buy pre-fabricated stringers from DIY shops or you can make your own from timber planks, we would advise using 6”x2” C16 pressure treated timbers.

You can use composite deck boards 2-up to make the step surface (also known as the ‘going’).

If you butt the boards together, then you will achieve a total ‘going’ of 276mm (total ‘going’ allowed is 223mm – 300mm). The ‘nosing’ or overhanging front lip of the step must be at least 16mm. The difference in height between 2 consecutive steps (also known as the ‘rise’) must be between 165mm and 200mm in this situation.

Ensure bearer spacing is 400mm max, 2 screws per board, per bearer.

Step sub-frame should be securely anchored to the ground, preferably on concrete pads.


Covering Concrete Steps

When covering concrete steps with AT Decking Boards , it is imperative to leave at least a 10mm drainage cavity under the deck boards and where the inside edge of the deck board meets the riser.

If you wish to clad the risers also, then you will need to lift that 10mm off the surface as well. This is to ensure that water has a free and easy route down the back of the AT Decking Boards  steps (& rise covers if fitted).

In this example, we have used our 10mm x 36mm insert strip as a packer between the concrete and AT Decking Boards , you could use any other waterproof media such as plastic or stiff rubber.  In this situation, you cannot use composite deck screws and must instead use a concrete approved screw such as ‘Tapcon®’.

The concrete screw must go through the decking, packer and into the concrete holding the whole assembly in compression. 2 screws per deck board, per packer.  You may have to check whether your steps comply with Building Regulations.


composite decking steps concrete construction

Safety Advice Note: We strongly recommend the addition of anti-slip, high-visibility stair nosings when constructing composite decking steps using AT21 boards