Updated October 2026
Glen Forrest was settled in the 1890s and is one of the village chain strung along Great Eastern Highway on the plateau. Older stock, established gardens and sloping ground make retaining walls a regular job here. We connect you with builders who cover the 6071 area.
Common wall situations in Glen Forrest
Replacement work dominates. Walls built decades ago with no ag-pipe and no gravel behind them reach the end of their life together, usually after a wet spell. The new work is driveway cuttings, shed and studio pads, and terracing to make a sloping block usable.
The Shire of Mundaring's strategy records reticulated sewerage in the hills as limited to the Mundaring town centre, so Glen Forrest properties run their own systems. The tank, the leach drains and the irrigation area are part of the site plan for any wall.
The ground under Glen Forrest
Rock, not sand, is what decides a price here. The City of Kalamunda has it in writing that hard granite sits close to the surface across the Hills and is costly to dig through, which is exactly the problem a post hole or an engineered footing runs into. Rock drilling or coring takes longer and costs more, and it is the most common reason a Hills quote reads above the Perth average.
Water is the failure mode. On ground where rock stops it draining down, it runs along the rock until it finds the back of a wall. A quote that does not itemise ag-pipe, gravel backfill, fabric and a discharge point is a cheaper wall that fails sooner.
What a wall costs in Glen Forrest
Guide pricing only: roughly $200 per metre at the timber end up to $700 or more per metre for stone and engineered block, for a wall about a metre high, from published Australian cost guides. Ground conditions and access move it more here than almost anywhere. See the retaining wall cost guide.
Approval, and who to ask in Glen Forrest
Approval in WA turns on 500mm of retained ground, not on the height of the wall, and the exemption only applies where the wall is also clear of other building work and is not holding up or affecting the land next door. All three have to be true at once. A wall on or at a boundary is dealt with separately under the Building Act and needs the neighbour's consent or another authority whatever its height. Development approval under the local planning scheme can apply as well, so confirm the position with the Shire of Mundaring before anything is quoted.
Who is allowed to build it is a statutory question in WA, and it turns on how the work is classified under the building legislation rather than on a figure you can look up and apply yourself. We are not going to settle that on a web page. What is worth doing is simple: ask the builder what registration or licence they hold, check it with Building and Energy, and ask your permit authority what your particular wall requires before you sign anything. Before any digging, your builder should lodge a free Before You Dig Australia (BYDA) enquiry so underground services are located.
Frequently asked questions
Why do so many walls here fail at once?
Because they were built the same way at the same time, without drainage, and the same wet spell loads all of them. Water, not weight, is what fails a wall, and rock close to the surface here means the water has nowhere to go but sideways into the back of it.
What is the longest lived option?
Concrete sleeper or engineered block, because there is nothing in them to rot. Timber is cheaper to build and will want replacing in fifteen to twenty-five years even when drained well.
Who is my permit authority?
The Shire of Mundaring. Note that it is a Shire, not a city or a council, which is the sort of detail worth getting right when you ring them.
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We also cover nearby Darlington and Mahogany Creek.