Sandstone retaining walls on the Northern Beaches

Most Northern Beaches blocks slope, and plenty of them sit on Hawkesbury sandstone a short way below the topsoil. A good retaining wall turns that slope into usable lawn, garden beds, a level driveway or a terrace, and a sandstone wall does it in the same stone the landscape is made of.

We build sandstone block walls from Manly to Palm Beach and across the North Shore, each on a sound footing with the drainage in before the backfill.

What we build

• Dry-stacked garden walls

  Low garden walls of rough-squared sandstone laid without mortar, which drain through their joints and suit natural, bushy gardens.

• Repairs and rebuilds

  Leaning or bulging sandstone walls taken down and rebuilt with new drainage, reusing the original stone where it is sound. See sandstone restoration.

• Sawn sandstone block walls

  Clean, square faces and tight joints for a crisp, contemporary look beside driveways, pools and modern homes.

• Rock-face and split-face block walls

  Textured, traditional faces that suit older homes, bushland blocks and coastal gardens.

• Terraced garden walls

  A series of lower walls that step a steep backyard into level, usable terraces and planting beds.

• Driveway and curved walls

  Walls that follow a sloping or curved driveway, including stepped-down tops and curved runs.

• Walls with built-in steps

  Sandstone block steps set into the wall so you can move between levels without a separate staircase.

Sawn or rock-face sandstone blocks?

Sawn blocks are cut on all faces, so they give straight lines, even courses and fine joints. They cost more than rough-cut stone and suit contemporary architecture. Common sawn block sizes are 300 x 300 x 1000 mm, 500 x 500 x 1000 mm and 500 x 500 x 2000 mm, with the larger blocks placed by machine on taller walls. See sawn, split-face and rock-face sandstone compared.

Rock-face and split-face blocks have a broken, textured face that throws shadow and looks at home next to bush and older houses. Rough-squared blocks can be dry-stacked for low garden walls and are usually the most economical choice.

Drainage and footings: why walls fail

Water is the main reason retaining walls lean, bulge or fall. When rain soaks the soil behind a wall and has nowhere to go, the pressure on the stone builds with every storm.

On the Northern Beaches the footing often means cutting into rock. Hawkesbury sandstone is frequently close to the surface, so trenches may need rock sawing or hammering to get a level, solid base for the first course.

• Free-draining backfill, such as clean gravel or crushed sandstone, directly behind the wall
• Geotextile fabric to stop soil clogging the drainage zone
• Slotted agricultural pipe at the base, falling to a legal discharge point
• Weep holes or drainage paths through the face where the design calls for them
• Stormwater connections made by a licensed plumber or drainer

Built for Northern Beaches slopes

Steep sites are common here, and many are mapped for landslip risk, bushfire or coastal hazards. On many Northern Beaches slopes a geotechnical report is needed before a significant retaining wall can be approved, and the engineer will set the footing, wall thickness and drainage. Our guide to retaining wall council approval on the Northern Beaches sets out the rules.

Built with proper drainage, a sandstone wall is effectively permanent. Sydney has sandstone walls well over 100 years old, while a timber sleeper wall typically lasts 15 to 20 years before it needs replacing.

Sandstone, timber or concrete block?

Timber sleeper walls are cheapest upfront but typically last 15 to 20 years. Concrete block systems are engineered and quick to lay, but the face never improves with age. A sandstone wall is solid stone all the way through: nothing rots or rusts, it drains through its joints, and it can be repaired or extended decades later with matching stone.