How to build steps attached to retaining wall?

Question

I'm building a set of steps attached to a retaining wall as per the attached image. I'm using steel H / C channels to secure the retaining walls which are marked in yellow. I'm not sure what to use for the areas marked in red through? Should I use something like a star picket behind the step corners to hold them in place? What screws / brackets should I use to assemble the steps and secure them to the retaining wall?

I eventually want to fill my steps and install pavers (likely not mortared in just with sand)

MitchellMc · Answer

That approach sounds like it would work well @devp. Using a steel corner channel at point C and then running a continuous sleeper through to F will give you a nice solid base and keep those key corners well restrained.

The main thing to keep in mind is that it’s not just about locking in the corners, you also want to make sure the top step is properly tied back to the lower structure so everything acts as one unit. That D/E area is where you’ll need to make sure there’s adequate support.

Using a treated pine post or even a solid sleeper offcut as a vertical support there is a perfectly reasonable solution. That will give you something substantial to fix into and help prevent any movement over time. If you go down that path, I’d suggest keeping those supports to the inside and hidden where possible, both for a cleaner look and to protect them a bit more from the elements.

Angle brackets can work for the lighter joins, but anywhere that’s taking load or tying levels together, having that solid post or backing piece will make a big difference to the overall rigidity.

Mitchell

devp · Answer

What if I was to use a steel corner channel at point C, and then run a continuous sleeper between C and F for the bottom sleeper? that would mean all the corners are secured and then I could just use the angle brackets for all the other corners. Only issue would be that D/E area..What if I put a treated pine post in behind the corner to secure them to? Or used a sleeper offcut as a vertical post on the outside?

MitchellMc · Answer

Hi @devp,

For the red-marked areas, you’ve basically got two workable approaches: either continue using the steel channel system for all structural junctions, or use heavy-duty landscape timber screws for some of the simpler joints where loads are less complex.

If you want a consistent and strongest build, I’d recommend staying with the steel system throughout. For areas A and B, you can use something like the

https://www.bunnings.com.au/ridgi-1-2m-x-60mm-x-60mm-galvanised-steel-c-end-post-upright-sleeper_p1080319

. This lets you fix the perpendicular stair riser back into the face of the existing sleeper. You would pre-drill the channel and fasten it into the sleeper face, then slide or fix your stair riser into place within the channel.

At point C, you can use the

https://www.bunnings.com.au/ridgi-0-65m-x-120mm-x-60mm-galvanised-steel-corner-post-upright-sleeper_p1080311

, which will handle the corner transition where two directions of sleepers meet cleanly and keep everything rigid.

For D, you can use the

https://www.bunnings.com.au/ridgi-0-65m-x-110mm-x-60mm-galvanised-steel-upright-sleeper-h-joiner-post_p1080305

for the lower sleeper connection, and then continue up to E using another

https://www.bunnings.com.au/ridgi-0-65m-x-120mm-x-60mm-galvanised-steel-corner-post-upright-sleeper_p1080311

to form the corner and support the riser transition.

Overall, I wouldn’t rely on star pickets behind the step corners. While they can help with basic retaining, they don’t give you the same rigid alignment and clean fixing points that the channel posts provide for stepped structures. The steel channel system is a much better option for keeping everything locked in square and preventing movement once you backfill and add the pavers.

For the joinery itself, standard heavy-duty landscape screws are fine where timber meets timber inside the channels, but anywhere structural or load-bearing, the steel uprights are the more reliable solution.

If you do need to use brackets, these

https://www.bunnings.com.au/carinya-190-x-75-x-50-x-6mm-galvanised-reinforcing-angle-bracket_p3961587

would be suitable.

Please let me know if you have any questions.

Mitchell