A retaining wall holds back soil, and its cost depends on how much wall there is, what it is made from, and how much groundwork the site needs. This guide shows how to estimate the wall area, compares materials, explains why drainage is non-negotiable, and covers when council approval and engineering are required.
A retaining wall holds back soil, and its cost is driven by three things: how much wall there is (length times height), what it is made from, and how much groundwork the site needs. Two walls of the same size can cost very differently depending on material and drainage, so the starting point is always the area of the wall face.
Estimate the face area with our square metre calculator, then apply the guidance below.
Wall face area (m²) = Length (m) × Height (m)
A wall 10 metres long and 1 metre high has a face area of 10 square metres. Most retaining wall products and quotes are priced per square metre of face, so this figure is the basis of every estimate. Remember to measure the full retained height, including any part below ground level.
Retaining walls are built from a range of materials, and price generally rises with durability and appearance. From most economical upward, common options include treated pine sleepers, concrete sleepers, besser (concrete) blocks, and natural stone or rendered masonry at the premium end. Timber is cheapest to install but has a finite life; concrete and masonry cost more upfront but last far longer, which matters for a structure meant to hold back earth for decades.
Water is the enemy of a retaining wall. Soil behind the wall holds water, and that water adds enormous pressure. A properly built wall includes drainage — usually an aggregate backfill and a perforated pipe (agi drain) behind it — to let water escape rather than build up. Skipping drainage to save money is the classic false economy: it is the leading cause of retaining wall failure, and rebuilding a collapsed wall costs far more than draining it correctly the first time.
Taller walls carry far greater loads and are not a DIY proposition beyond modest garden-bed heights. An engineered wall costs more but is the difference between a structure that stands for decades and one that fails dangerously. Where a wall retains soil near a boundary or building, professional design is not optional.
Because so much depends on the site, the reliable path is to fix your wall area, decide on a material, then get two or three local quotes that include excavation, drainage and disposal — not just the wall face. Ask each quote to itemise groundwork separately, so you can compare like with like. Our concrete calculator helps if you are pricing a concrete-based wall or footing.
A low garden retaining wall — a couple of sleeper courses to level a bed — is within reach of a capable DIYer. Anything structural, tall, or near a boundary or building belongs with a professional and, above the council threshold, an engineer. The cost of getting a structural wall wrong is measured not just in dollars but in safety, so match the wall to your genuine skill level.
How do I estimate retaining wall cost?
Start with the wall face area — length times height in metres — since most walls are priced per square metre of face. Then factor in the material, plus excavation, drainage and soil disposal, which together often cost as much as the wall itself.
What is the cheapest retaining wall material?
Treated pine sleepers are usually the most economical to install, followed by concrete sleepers, besser blocks, and natural stone or rendered masonry at the premium end. Timber is cheapest upfront but has a finite life, while concrete and masonry last far longer.
Why does a retaining wall need drainage?
Soil behind the wall holds water, which adds enormous pressure. Drainage — an aggregate backfill and a perforated pipe — lets water escape rather than build up. Skipping it is the leading cause of retaining wall failure, and rebuilding costs far more than draining correctly.
Do I need council approval for a retaining wall?
Often yes. Many councils require a permit and an engineer's design for walls roughly a metre or higher, or where the wall supports a structure. Thresholds vary, so check with your local council before building.
Can I build a retaining wall myself?
A low garden wall of a couple of sleeper courses is achievable for a capable DIYer. Anything structural, tall, or near a boundary or building needs a professional and, above the council threshold, an engineer — the cost of getting a structural wall wrong is a safety matter.