Retaining wall cost: prices per metre

A retaining wall usually costs $250 to $400 a linear metre in timber sleepers, $450 to $650 a metre for a 600mm sandstone block wall, and from about $750 a metre for an engineered wall over 600mm, plus engineering and approval fees. Those are installed prices from our own jobs in Newcastle and Lake Macquarie, with drainage included.

Height changes the price more than anything else, followed by access, the ground behind the wall and what has to come out first. Here's how retaining wall cost is worked out, what you are paying for in each metre, and how to tell a fair quote from a cheap one that will lean in five years.

How much does a retaining wall cost per metre?

Wall	Typical installed cost
Timber sleeper wall, low	$250 to $400 a linear metre
Sandstone block wall, 600mm, with drainage	$450 to $650 a linear metre
Engineered wall, over 600mm	from about $750 a linear metre, plus engineering and approval fees

Prices are a guide, + GST, installed and cleaned up.

Concrete segmental block sits alongside sandstone for low walls and is the system engineers usually choose for tall ones, because the blocks lock together and can take reinforcing grid back into the soil. We price it per job, because the colour, the block size and the engineer's design all change it.

Prices in other cities differ with labour rates and stone supply, but the way a wall is priced is the same everywhere: by the linear metre, at a given height, with the footing and the drainage in the rate.

What are you paying for in each metre?

Most of a retaining wall is underground or behind the face, which is why a wall costs more than the blocks stacked on top of each other. Every metre we quote includes:

• Excavation to cut the slope back and make room for the footing and the drainage behind the wall.
• A compacted footing, because a wall is only as straight as what it sits on.
• A slotted ag pipe along the base, running out to a pit or a legal discharge point.
• Clean gravel backfill behind the wall, wrapped in geotextile fabric so the soil can't clog it.
• The wall itself, laid level, with capping on block and sandstone.
• Taking away the spoil, the soil and rubble that come out of the hole.

The drainage is the part people are tempted to cut. Don't. Water is what pushes walls over. Soil behind a wall gets much heavier when it's wet, and a wall with no way for that water to escape leans, bows or cracks, especially on clay. Our page on retaining walls in Newcastle explains how we build and drain a wall step by step.

Why does height change the price so much?

The deeper the soil, the harder it pushes. Double the height of a wall and the force on it rises much faster than double, so the footing has to be bigger, the drainage has to carry more water and the wall usually needs reinforcing. That's why a 1.2 metre wall costs far more than two 600mm walls of the same length.

There is a rule in NSW that sits right at that line too. A retaining wall up to 600mm high can be exempt development under the State's Codes SEPP, meaning no council approval, if it meets every condition, including at least 1m from each lot boundary, at least 2m horizontally from any other retaining wall, drainage lines connected to your stormwater, and not on a heritage item or a flood control lot. Above 600mm you need a complying development certificate or a development application, and an engineer's design. That adds the engineer's fee, the approval fee and the wait for approval to the cost of the wall itself.

If you live in the Hunter, check one more thing. Large parts of Newcastle and Lake Macquarie are in mine subsidence districts, and work there that needs council approval may also need approval from Subsidence Advisory NSW. A low exempt wall usually doesn't. A tall engineered wall might.

What else pushes the price up?

Access. If a small excavator can get in beside the house, a wall goes up quickly. If every block and every tonne of gravel has to go through a gate by wheelbarrow, or up a set of stairs, labour climbs.

What's already there. Pulling out an old sleeper wall has to be done in sections so the soil behind it doesn't slump. Old concrete, tree roots and buried rubble all take time to remove and money to dispose of.

Rock and clay. Sandstone bedrock close to the surface is slow to dig. Heavy clay doesn't drain, so it needs more gravel and pipe behind the wall.

Shape. Straight runs are cheapest. Curves, corners, steps built into the wall and returns at each end all add time.

Services. Pipes and cables have to be located before anyone digs. Lodge a free enquiry with Before You Dig Australia before the job starts, or ask your landscaper to.

Three walls, priced

These are rough figures from the rates above, to show how the numbers add up. Your quote will differ with height, access and ground.

• A 10 metre sleeper wall along a low garden bed: about $2,500 to $4,000.
• A 15 metre sandstone block wall at 600mm to level a backyard: about $6,750 to $9,750.
• A 10 metre engineered wall at about 1.2 metres holding up a steep bank: from about $7,500, plus engineering and approval fees.

The third one is where it pays to ask about stepping. Two lower walls with a planted bed between them can sometimes do the same job and give you a level garden bed as well. They stay exempt from approval only if each is 600mm or lower, they are at least 2m apart measured horizontally, each sits at least 1m from the boundary, and both have drainage connected to your stormwater. Whether that fits depends on how much room you have from top to bottom of the slope, which we measure at the site visit.

How do you tell a fair quote from a cheap one?

A cheap wall is usually cheap because something has been left out. Look for these in every quote you get:

• Drainage named. Ag pipe, gravel, geotextile and where the water goes. If a quote just says "retaining wall, 15 metres", ask what's behind it.
• Steel posts for sleepers. Sleeper walls should sit on galvanised steel posts concreted into the ground. Timber posts in wet soil rot first.
• The height and the approval. If the wall is over 600mm, the quote should include the engineer's design and the approval, or say clearly that they are extra.
• A contractor licence number. Retaining walls are structural landscaping, and in NSW structural landscaping over $5,000 needs a contractor licence from NSW Fair Trading. You can check the number online.
• A written contract and a fair deposit. For licensed work over $5,000 in NSW there must be a written contract, and the deposit can't be more than 10 per cent of the price.
• The statutory warranties. Under the NSW Home Building Act, home building work carries warranties of 6 years for major defects and 2 years for all other defects, from completion.
• What happens if something turns up. Old footings, buried concrete or a pipe that isn't on any plan. A good builder stops and talks to you before the price changes.

Which material should you choose?

Choose sleepers for low garden beds and walls you're happy to replace one day. Choose sandstone block where the wall is part of the look of the garden, especially on older houses, because it weathers well and looks better each year. Choose concrete block for taller or engineered walls, where the system matters more than the finish. If the wall holds up a driveway, a shed or a neighbour's yard, let the engineer decide.

A retaining wall often comes with other work around it, like steps, a path along the top or a paved area at the base. Our page on paving in Newcastle covers the options, and our landscaping cost guide shows how a wall fits into the price of a whole backyard.

Get your wall priced

The rates above tell you roughly what to budget. The exact figure comes from the height, the length and the ground, which we can only see on site. We build retaining walls across Newcastle and Lake Macquarie, and the site visit and quote are free. Book a site visit and we'll measure the slope, tell you whether your wall needs approval, and send a fixed, itemised price.