Link blocks and besser blocks get confused constantly, partly because both are precast concrete masonry units sold through the same landscape supply yards, and partly because “besser block” has become a loose catch-all term in Australia for almost any concrete block product. But for a retaining wall in the Blue Mountains, the two are genuinely different products with different structural capabilities, and using the wrong one for the height of retaining you actually need is one of the more common DIY mistakes we get called out to assess.
This guide sets out what each product is, where the real structural line sits between them, and why that line matters more here than in a flat, dry-climate suburb.
What Is a Link Block?
A link block, sometimes sold as a “link wall block” or under a supplier’s own branding, is a small precast concrete masonry unit designed to interlock with the block above and below it through a moulded lip, notch, or “H” profile, without mortar and, in most residential product lines, without steel reinforcement or a poured concrete core. The blocks simply stack, dry, on a compacted base.
Link blocks are aimed squarely at the home-handyman garden edging and low retaining market, sold at hardware and landscape supply yards, and marketed on ease of installation: no mortar, no formwork, no trade skill required to get a straight, stable-looking course.
Typical characteristics: gravity-only structure with no steel reinforcement or poured concrete core in the standard residential product; stacks dry on a compacted gravel or sand base, with no footing in the structural sense; manufacturer guidance almost always caps unsupported height well below 1 metre, often at 600mm or less for retaining rather than purely decorative use; low cost per unit and fast to install without specialist equipment.
What Is a Besser Block?
Besser block, named for the Besser Company that pioneered the hollow concrete masonry unit, is a genuine structural masonry system when used correctly for retaining. The blocks themselves are hollow-core precast units, typically 390mm x 190mm x 190mm, but the retaining wall is built from the blocks plus steel reinforcement inserted into the hollow cores and concrete poured in to fill them, sitting on a proper poured concrete strip footing sized for the wall height and soil load.
Typical characteristics: hollow-core blocks act as permanent formwork for a reinforced concrete core, with vertical steel reinforcement at engineered centres, usually around 400mm, and a poured concrete footing sized to the specific height and soil conditions; engineered for heights up to around 1.5 metres in standard residential applications, more with specific engineering; requires trade skill and, beyond a low garden wall, an engineer’s input.
See our Block and Besser Retaining Walls service page for the full detail on how these are built for structural retaining.
The Key Differences at a Glance
| Factor | Link Block | Besser Block (reinforced) |
|---|---|---|
| Reinforcement | None (standard residential product) | Steel bars in grouted cores |
| Footing | Compacted base, no poured footing | Poured concrete strip footing |
| Realistic max height for retaining | Around 400-600mm | Up to 1.5m+ with engineering |
| Structural basis | Gravity/mass only | Reinforced masonry, engineered |
| Drainage compatibility | Limited, joints aren’t a real drainage path | Good, with ag pipe and aggregate backfill |
| Typical use | Garden edging, very low terracing | Genuine structural retaining |
| Installation | DIY-friendly | Trade skill, engineering for taller walls |
| Cost per linear metre | Lowest of the masonry options | $450 – $1,400 depending on height and finish |
Why the Height Line Matters More in the Blue Mountains
A link block wall kept genuinely under around 500 to 600mm on a well-drained, gently sloping site in a low-rainfall area can perform adequately as garden edging for years. The Blue Mountains changes that calculation in two ways.
Rainfall and saturated clay. Much of the region sees 1,000 to 1,400mm of rain annually, and clay and clay-loam soils are common across the lower and mid mountains. Saturated soil exerts significantly more lateral pressure than dry soil, and a gravity-only, unreinforced block system has very little margin to resist that extra load beyond the manufacturer’s low-rainfall design assumptions. A link block wall that would sit quietly for a decade in a dry inland climate can start to lean or bow within a couple of wet seasons here.
Slope, not flat ground. Most Blue Mountains blocks needing a retaining wall have genuine slope, not the flat backyard link blocks are really designed for. Retained soil height is rarely as modest as it first looks once the slope continuing above the visible wall face is accounted for, and it’s easy to end up needing more retained height than a mortarless gravity system can safely provide.
The height threshold where link blocks stop being appropriate, and a genuinely engineered system becomes necessary, usually arrives sooner on a Blue Mountains block than the packaging suggests. Conveniently, this structural ceiling also sits close to the 600mm exempt-development threshold across most Blue Mountains LGAs, so a link block wall used strictly within its limits will usually avoid needing council approval too. The classic mistake is stacking link blocks to 900mm or more to solve a bigger retaining problem than the product was designed for.
Drainage: The Other Real Limitation
Reinforced besser block, like concrete sleeper, is built with a proper drainage specification behind it: geotextile fabric, aggregate backfill, and ag pipe at the base directing water away rather than letting it build up behind the wall face. Link block systems are rarely installed with this level of drainage discipline, partly because the product is marketed as a simple DIY job, and partly because the joints between dry-stacked link blocks aren’t a reliable long-term drainage path in the way dry-stone sandstone joints are.
Without proper drainage, hydrostatic pressure builds behind any wall over time. On an unreinforced gravity system with no engineered resistance to that extra load, this is the most common failure mode: bowing, then toppling, of a link block wall that was doing fine until a wet winter pushed the saturated soil load past what the stacked blocks could resist.
When Link Blocks Are a Reasonable Choice
Used within their actual design envelope, link blocks aren’t a bad product, they’re simply a limited one. They’re a sensible, low-cost choice for genuine garden edging with minimal retained height (well under 500mm), low terracing on flat or gently sloping ground with good existing drainage, non-structural decorative applications like planter surrounds or low seating walls, and short-term or budget projects where the owner understands and accepts the product’s limits.
They’re not the right product for anything genuinely retaining a slope, supporting a driveway, sitting near a building, or facing the sustained rainfall and clay conditions common across the Blue Mountains.
Comparing Costs
Link block cost is low, generally the cheapest masonry option per linear metre for a low, unreinforced course. But that only makes sense for equivalent scope, once a project needs the height, reinforcement, footing, and drainage a real Blue Mountains retaining situation demands, the comparison is really link block (inappropriate) versus reinforced besser block or concrete sleeper (appropriate), not a straight per-metre price comparison.
For reinforced besser block walls, indicative 2026 pricing runs from around $4,000 to $7,500 for a small unrendered wall up to 900mm, rising to $13,000 to $25,000 for a large 20m-plus wall over a metre. Concrete sleeper sits in a similar range and is the more commonly chosen structural alternative, see our Concrete Sleeper Retaining Walls guide for how that system is engineered and drained for this region. For a broader comparison including sandstone and timber, see our Retaining Wall Materials Guide. If what you actually want is the dry-stacked, no-mortar build a link block promises but at a genuine retaining height, see our guide to modular concrete block retaining walls and geogrid design, which is the engineered version of that idea.
Frequently Asked Questions
Can I use link blocks to retain a slope higher than 600mm on my Blue Mountains property? We wouldn’t recommend it. Beyond around 500 to 600mm, an unreinforced gravity block system generally doesn’t have the margin to reliably resist the lateral soil pressure typical of this region’s rainfall and soil conditions. A reinforced besser block, concrete sleeper, or sandstone wall is the appropriate choice once you’re genuinely retaining a slope rather than edging a garden bed.
Is a besser block wall just a link block wall with mortar added? No. A structural besser block retaining wall has steel reinforcement grouted into the hollow cores and sits on a poured concrete footing sized to the wall height and soil load. Mortar joints alone, without that reinforcement and footing, wouldn’t turn a link block system into an engineered structure.
I’ve already got a link block wall that’s starting to lean. Can it be fixed, or does it need replacing? Usually replacing. A wall showing early bowing is responding to saturated soil load it was never designed to resist, and in most cases the durable fix is a properly engineered system rather than reinforcing a gravity-only structure after the fact. The specific situation needs assessing before either path is recommended.
Do link block walls need council approval in the Blue Mountains? If kept within their appropriate height range, generally under 500 to 600mm, they typically fall under the same exempt development thresholds as other low walls. The question tends to become moot because link blocks aren’t a sound choice for anything taller, which is usually where DA or CDC requirements start to apply anyway.
Not sure which product is right for your Blue Mountains project? Send us photos of the slope and we’ll give you an honest recommendation, not just a quote for whatever’s easiest to sell. Request a free quote →