Tierline Retaining Walls Link-Block (Segmental) Walls
Link-block is an interlocking segmental block system, Allan-block or Versaloc style: mortarless concrete blocks that stack and lock together, often with geogrid tying the wall back into the slope. They curve beautifully, suit garden terraces and sloped blocks, and go up cleanly. The system only performs if the geogrid and the drainage are done to spec, which is exactly where a cheap install cuts corners, so we build them the way they are designed to be built, not just stacked.
What this job includes.
- ✓Interlocking segmental (link-block) retaining walls, Allan-block and Versaloc style
- ✓Engineered geogrid layers tying the wall back into the retained soil
- ✓Curved and stepped to follow a winding garden terrace or contour
- ✓Aggregate drainage behind the blocks, ag-pipe and geofabric
- ✓Structural design where the height or a surcharge needs it
A link-block wall is a system, not a stack
Link-block is an interlocking segmental block system: mortarless concrete blocks that stack and lock together, often with geogrid reinforcement running back into the retained soil at engineered intervals. Built the way the system is designed, a link-block wall curves beautifully, suits a sloped or terraced garden, and lasts decades. Built as just stacked block with no geogrid and no drainage, it is the cheap quote that leans out within a few seasons. The difference is whether the engineered reinforcement and the drainage are on the page or skipped to win the price.
What the geogrid actually does on a slope
The geogrid is what stops the wall sliding out as the retained soil tries to slump downhill. It runs back into the soil at the intervals the system calls for (every second or third course, typically, depending on the height and the load above), and it is the difference between a wall that holds a sloped Adelaide Hills block for 30 years and one that bulges in winter three. We set out the geogrid pattern from the engineer’s design, name it on the quote with the layer spacing and the grade, and lay it as the wall comes up, never tacked on at the end.
What an itemised link-block quote includes
- The wall measured by face-metre (length by height), priced per face metre with the block type (Adbri, Boral or Versaloc) and the cap detail named on the page
- The engineered geogrid layers, the grade and the spacing, sized to the wall and the load above
- The free-draining aggregate column directly behind the blocks, the ag-pipe at the base, and the geofabric between the aggregate and the retained soil
- The base preparation: the compacted aggregate levelling course the first course sits on, set out level and to the curve
- The structural engineer design line where the wall retains over a metre or carries a surcharge above
- The council development approval where the height needs it, prepared and lodged with the engineer design
- The excavation, the spoil cartage and the access on a steep or tight block, each itemised
- The 10-year structural and drainage warranty, in writing
Link-block is a forgiving system when it is built to spec. It is also the most-skipped system in the Hills, because two of the four things that make it work (the geogrid and the aggregate drainage) are invisible once the wall is finished. The quote is where you tell which kind of link-block wall you are buying.
Priced by the face-metre, itemised line by line.
The face-metres and height, the material and the footing named, the drainage as its own line, the engineering and council line if it is over a metre, excavation and access, and the boundary note if the wall holds up a neighbour. Not one round number for a wall.
- 1 Face-metres, height and material. The price broken down by face-metres and the wall height, with the material named: concrete sleeper, core-filled besser, timber, link-block or stone. Not one round number for "a retaining wall".
- 2 The footing and reinforcement. The footing sized to the wall and the soil: a reinforced concrete footing for besser, concrete-set posts dug to depth for sleeper walls, with the reinforcement named. This is the line cowboys skip.
- 3 The drainage, as its own line. The ag-pipe (subsoil drain) along the base, the free-draining aggregate backfill, the weep holes and the geofabric. Trapped water is the number one reason walls fail, so the drainage is on the quote, not left off.
- 4 The engineering and council line. If the wall retains over a metre, the structural engineer design and certification and the council development approval, itemised, with a realistic approval timeline, not folded into a round number.
- 5 Excavation and access. The cut, the machine access on a steep or tight block, the spoil carted away and the tip fees, each a line, never sprung on you at the end.
- 6 The boundary-cost note. If the wall holds up a neighbour boundary, a plain-English note on how the cost usually falls (the benefit / whose-land-is-retained rule), so you can have the conversation. General guidance, not legal advice.
- 7 Warranty and compliance. The 10-year structural workmanship and drainage warranty in writing, and the AS 4678 / NCC compliance with the engineer design where the height needs it.
What happens, step by step.
Free site assessment and soil
We come to the block, measure the fall and the slope, check the soil and the access, and talk through material and height, then put a written quote in your hands.
Engineer design where the height needs it
For a wall over a metre or under a surcharge, the structural engineer designs it to AS 4678 and we lodge the council development application, so it is signed off before we dig.
Itemised quote and start date
The honest quote: face-metres, height and material, the footing, the drainage, the engineering line, excavation and the boundary-cost note. You sign off and we book the dig.
Footings and posts
We excavate, then size and set the footings: a reinforced concrete footing for besser, concrete-set posts dug to depth for sleeper walls. The footings cure before the wall goes up.
Drainage and wall build
The ag-pipe and free-draining aggregate go in behind the wall as it is built, with weep holes and geofabric, so water drains away instead of building up. Then the wall is built to height.
Backfill, finish and handover
We backfill and finish, clear the site, walk you around the wall, and hand over the warranty in writing and the engineer certification and approval paperwork where it applies.
The paperwork behind the price.
Public liability to $20M, and a 10-year structural warranty, all in writing, all on request.
We hold a South Australian builder’s licence, we build every wall to AS 4678 and the NCC, and we carry public liability insurance, so you are covered on site. For a wall over a metre, or one holding up a driveway or a building, we bring the structural engineer’s design and certification and handle the council development approval. The guarantee is a 10-year structural warranty, in writing, covering the structural workmanship and the drainage, the parts that fail first. All in writing, with exclusions named.
Link-Block (Segmental) Walls: common questions.
What is a link-block wall?
Are link-block walls strong enough for a sloped block?
Can link-block follow curves and steps?
Do they need drainage and geogrid?
Get a free, itemised quote you can actually read.
Tell us what you need. We’ll book a walkthrough and send a quote with the work itemised, not just a number.