Retaining Walls Perth Hills | Kalamunda & More

Retaining Walls for Perth Hills Properties

Up on the Darling Scarp the sand gives way to gravel, clay and granite. Walls in Kalamunda, Lesmurdie, Mundaring, Roleystone and nearby suburbs deal with slope and runoff more than loose sand.

Councils	City of Kalamunda, Shire of Mundaring, City of Armadale (hills), City of Swan (hills)
Ground	Lateritic gravel and clay over granite, with boulders and steep slopes on the Darling Scarp
Walls we see most	Stone and block walls on cut slopes, engineered walls below driveways, drainage-led repairs

Councils

City of Kalamunda, Shire of Mundaring, City of Armadale (hills), City of Swan (hills)

Ground

Lateritic gravel and clay over granite, with boulders and steep slopes on the Darling Scarp

Walls we see most

Stone and block walls on cut slopes, engineered walls below driveways, drainage-led repairs

Different ground up the scarp

Most of Perth sits on sand, but the hills do not. Along the Darling Scarp and the plateau behind it, through Kalamunda, Lesmurdie, Gooseberry Hill, Forrestfield's upper slopes, Darlington, Glen Forrest, Mundaring, Roleystone and Kelmscott's hills, the ground is mostly lateritic gravel and clay over granite. Large boulders are common, and many blocks are steep.

That changes the job. Excavation can be slow and noisy where rock is close to the surface. Clay holds water rather than letting it drain away. And on a slope, every heavy rain sends water across the surface towards the nearest wall.

Slope and runoff

In the hills, the biggest threat to a retaining wall is water running down the slope. A wall that blocks surface runoff becomes a dam unless the water is caught and moved. Good designs usually:

Intercept surface water with a dish drain, swale or spoon drain above the wall
Include a drainage layer and slotted pipe behind the wall
Discharge collected water to a point that will not cause erosion or flood a neighbour
Avoid directing roof or driveway water into the ground directly behind the wall

If a quote does not explain where the water goes, ask.

Driveways and house pads

Many hills homes sit on a cut-and-fill pad with a steep driveway, and walls along driveways and below house pads carry significant loads. These are the walls most likely to need engineering and a building permit. An engineered block or reinforced masonry wall, or limestone or stone built to an engineer's design, is common for these jobs.

Stone and the hills look

Natural stone suits the bushland setting of the hills well, and many older properties have dry-stacked stone or rock walls. For lower garden walls, limestone blends in reasonably well, while some owners prefer to use granite rocks from their own excavation for a more natural look. Taller walls can be faced in stone over a reinforced core.

Bushfire-prone land

Much of the Perth Hills is designated bushfire-prone. If your property has a bushfire attack level assessment or is in a designated area, check whether that affects your choice of materials near the house. Timber sleepers are combustible; masonry and steel are not. Your local government can tell you what applies to your site.

Old walls on hills blocks

Older hills properties often have walls that were built informally, from rock or timber, without drainage. Those walls commonly show their age as bulging, timber rot, or soil washing through after storms. Our repairs page explains how builders usually decide between fixing and rebuilding.

Talk to us about your hills block

Call 08 7666 2963 or use the form. Tell us the suburb, the slope, what is above and below the wall and what access is like. A local builder will look at the site and give you a written quote. Approvals are covered in our council guide, and the cost guide has planning ranges.

Walls we arrange in the Perth Hills

Limestone Retaining Walls Cut and reconstituted limestone block walls, the Perth default for sand pads, boundary level changes and garden terraces.

Concrete Sleeper Walls Steel posts concreted into the sand with concrete sleepers dropped between them. Slim, quick to build and easy to put a fence on.

Timber Sleeper Walls Treated pine or hardwood sleepers for low garden walls and raised beds, where a softer look matters more than a long service life.

Block & Engineered Walls Interlocking segmental blocks and reinforced core-filled masonry for taller cuts, driveways and anything carrying a load.

Retaining Wall Repairs Leaning, bulging, cracked or washed-out walls assessed, then repaired, partly rebuilt or replaced.

Questions people ask before they commit

Is building a retaining wall in the hills more expensive?

Often, because of slope, access, rock and the need to manage runoff. Steep driveways, boulders in the excavation and taller walls all add time. The only way to know is a site visit.

What happens if the builder hits granite?

Rock may need breaking or the wall line may be adjusted to work with it. In some cases sound rock makes a good base. A builder who has seen the site can explain the options and price them.

Can timber walls be used in bushfire-prone areas?

Timber is combustible, so if your property is in a designated bushfire-prone area or has a bushfire attack level assessment, ask whether a non-combustible wall is the better choice near the house. Your local government can tell you whether bushfire requirements apply to your site.

How is stormwater handled behind a hills retaining wall?

Usually with a combination of a drain or swale above the wall to catch surface runoff, a drainage layer and pipe behind the wall, and a planned discharge point downhill. The outlet must not simply send the problem onto a neighbour's land.