The elevated split timber decks attached to this house were separated by a 480mm height difference, a distance too great for even the longest legs to step over comfortably. The solution was to divide the height by three to install two steps with three risers of equal 160mm increments.
The steps run 4800mm long, providing access along the entire platform plus informal seating.
The bearers and joists are of 70 x 45mm treated pine with the rear base bearer doubled for extra support.
The timber sizes worked well with the height of the steps, with the bearer and joist totalling 140mm, then the 20mm blackbutt decking timber creating the riser height of 160mm.
The width of the treads was set at 275mm to allow four decking boards with 3mm gaps between them.
STEP 1: Set out the base step
Cut the bearers and joists using a circular saw or sliding compound mitresaw. Use a builder’s square to set out a 4800 x 530mm rectangle for the base step bearers and set stringlines so they run straight.
STEP 2: Secure the base bearers
Position the base bearers, using a spirit level and adjusting with packers if required then securing them to the hidden joists beneath the existing decking by skew-nailing either side with 100 x 3.75mm galvanised bullethead nails.
STEP 3: Add joists and extra slats
Position the base joists at 450mm centres along the base bearers, securing by skew-nailing either side with 75 x 3.75mm galvanised nails.
TIP Maintain the height of the step by securing two support slats across the joists exactly beneath the top bearer.
STEP 4: Add the second step
Position the top bearers on the secured slats and skew-nail either side into the base joists with 75mm galvanised nails, repeating the setout for the top joists and securing to the top bearers with skew nails.
STEP 5: Cut and drill the rises
Cut the riser decking for both steps with a 20mm mitred overhang at the ends, and mitres at the joints centred over the joists. Secure the joints with construction adhesive and to the joists with two 50 x 2.8mm twisted galvanised decking nails.
STEP 6: Secure the tread decking
Position the tread slats for each step with square-cut butt joints centred over the joists, drilling pilot holes to prevent splitting and securing with two decking nails at the joists. Enclose the step ends with four mitred slats using adhesive and decking nails.