How to build outdoor stairs?

archerwinmakes

Hi. My friend asked me to help him build a timber outdoor staircase with a height of 2.7m.

I've read the regulations (AS1657) and choose the following:

riser = 225mm

going = 240mm

I've mocked up the stringer and if I use 240 x 45 treated pine, I will have around 75mm of timber left after I cut the riser and going.

Is 75mm enough to support the weight? thanks!

MitchellMc

Hi @archerwinmakes,

75mm does not seem enough to me. I can't imagine that would support my body weight, let alone include the entire weight of a staircase or multiple people using it simultaneously. I've looked at various designs, and in many instances, the amount of timber left to support the staircase is equivalent to the rise. Have a look at the rendering I've put together below. You'll see how the red rectangle formed by the rise and fall is able to fit in the remaining timber. Unless you're going to have posts incorporated into this design, I don't feel the 75mm you've left will be sufficient. Your design seems more similar to an internal staircase with structural timber beneath it to provide support. I've also included another option where you could rebate the stair treads into the stringer, similar to our treated Pine staircases.

By my rough approximation, the timber you leave should be closer to 180mm.

Please let me know if you have any questions.

Mitchell