Landscape stairs - how to anchor to ground over compacted drainage gravel?

ChrisWWW

Hi everyone,

First-time questioner, long-time reader here!

I have two main questions (that I’m aware of — this may open a can of worms!) related to upgrading our outdoor space and managing waterproofing at foundation level.

Question 1: Installing Landscape Steps Over Drainage Gravel

We’re upgrading our outdoor area and incorporating exterior waterproofing. As part of this, we’ll have a gravel path sitting above geofabric-wrapped drainage gravel, which covers the foundation drainage.

We’d like to install landscape-style timber stairs (see attached image for reference). Normally, these stairs require rebar—typically 450 mm long—driven through the riser posts into the ground for anchoring. However, one side of our steps will sit directly above the drainage gravel, meaning there’s no firm soil below for anchorage.

How can we construct the steps securely in this situation?
I understand one option is to move the steps roughly 600 mm away from the wall so they sit entirely over compacted earth, but ideally, we’d like to keep the stairs under the eaves for shelter from rain.

Question 2: Protecting the Waterproofing and Drainage Board

If we do keep the steps close to the wall, I’d prefer not to attach them to the brickwork since the wall will be covered in a dimpled drainage board as part of the waterproofing system. Any movement in the stairs could damage that layer. Is there a way to protect the drainage board while keeping the stairs close to the wall?

Project Details

• Wall length: 7.4 m

• Total rise: 1.8 m

• Stair dimensions:

  • Material: 150 × 150 mm H4 pine posts

  • Rise per step: 150 mm

  • Run per step: 360 mm

  • Approx. 12 steps, overall stair length ~4.32 m

  • 1.5 m landings at top and bottom

• Planning to include a handrail along the brick wall to comply with Australian Standards.

• For the picture used the stairs were added in using ai, so not the best reflection of what we want the timber stair picture is much closer. 

Open to Alternatives

If there’s a better approach or different stair construction method suited to this setup, I’d love to hear suggestions! Bear in mind I’m hoping to avoid using concrete or any non-permeable materials, and to be able to complete the project as a DIY build.

Thanks so much in advance — really appreciate the wisdom shared in this forum!

EricL

Hello @ChrisWWW 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about installing landscape stairs.

I understand that you want the stairs covered under the eaves, but the consequence of covering the foundation drain makes this a non-negotiable installation. The stairs must be installed away from the foundation drain. This automatically removes installation issues and will not interfere with the proper operation of your drain. To protect the stairs, I suggest building a simple light duty rain/sun cover. Imagine a narrow timber pergola running from one end to the other.

The only other approach that comes to mind is to build it as regular timber steps but floating above the foundation drain. This will involve the steps being anchored to the brick wall using a ledger and one side will have posts buried in the ground like decking posts. It will need to be built high enough that it will not interfere with your drainage board.

Let me call on our experienced members @Dave-1, @Nailbag and @AlanM52 for their recommendations.

If you need further assistance, please let us know.

Eric