Why Sub Base Preparation Is the Most Important Part of Any Paving Project in Melbourne

25 May 2026

Most paving fails because of what's underneath, not what's on top


When people look at a finished paved courtyard, they see the stone. The colour, the pattern, the way the joints line up. What they don't see is the six inches of structure underneath that actually decides whether the paving will still look that good in twenty years, or whether it'll be cracked and uneven inside two.

Sub base preparation is the part of a paving job nobody photographs. It's also the part that separates premium landscape construction from work that looks fine on day one and falls apart by year three.

This post walks through what proper sub base preparation actually involves, why it matters so much in Melbourne specifically, and what to look for when you're getting quotes for a paving project.

What sub base preparation actually means

For most premium paving jobs in Melbourne, especially in inner suburbs like Toorak, South Yarra, East Melbourne, Prahran and Carlton where heritage homes and tight courtyard spaces are common, the sub base is a proper engineered concrete slab. Not crushed rock. Not compacted soil. A reinforced concrete slab built to spec, with proper formwork, reinforcement mesh on bar chairs, and a clean pour.

The process looks like this:

Formwork. Timber formwork is built to the exact dimensions of the finished paved area. The formwork sets the perimeter, holds the concrete in place during the pour, and establishes the levels the slab will be poured to. Get the formwork wrong and the slab pours out of level or out of square, and every problem from that point gets worse.

Reinforcement. Steel mesh is laid across the slab area and lifted off the ground on bar chairs. The bar chairs are small plastic spacers that hold the reinforcement at the right depth within the slab, usually around the middle third. Reinforcement on the ground is reinforcement in the wrong place. It needs to be inside the concrete, not under it.

The pour. Concrete is poured to the level set by the formwork, screeded flat, and finished. For a paving sub base, the surface doesn't need to be polished, but it does need to be level and clean. Once it cures, this slab becomes the platform every paver sits on.

Drainage falls. A good sub base isn't dead flat. It's pitched, usually one or two per cent, so water runs off the surface and into drainage points instead of pooling under the pavers. Get the falls wrong and you'll have water sitting on the slab forever.

Pavers laid on adhesive. Once the slab has cured properly, the pavers are laid on a tile adhesive bed, often after being dry-laid first to check the pattern and fit. For an ashlar pattern, which uses different-sized rectangles fitted together, dry-laying is essential. You can't improvise that pattern on the fly.

The total time investment for proper sub base work on a typical inner-Melbourne courtyard is often longer than the actual paving installation. That's the part that surprises clients, but it's also the part that determines whether their investment lasts.

Why this matters more in Melbourne than most places

Melbourne's climate is the reason sub bases either succeed or fail. Wet winters saturate the ground. Dry summers shrink it. The freeze-thaw cycles you get in colder climates aren't a major factor here, but the wet-dry cycle is brutal on anything sitting on poorly prepared ground.

Compacted soil moves. Crushed rock bases without proper drainage become saturated and lose their bearing capacity. Pavers laid straight onto either of these will eventually:

  • Lift at the edges as water gets under them and freezes or expands
  • Sink in spots where the base has been compressed by foot traffic or furniture
  • Crack along joint lines as the substrate shifts unevenly
  • Develop puddles in low points that should have drained but didn't

A reinforced concrete slab solves all of this. The slab itself doesn't move with the ground. The reinforcement prevents cracking even if minor settlement occurs underneath. The drainage falls keep water moving off the surface. The pavers, sitting on adhesive on a stable platform, stay exactly where they were laid.

This is especially important in the inner Melbourne suburbs CHS works across. Heritage homes in Toorak, South Yarra, East Melbourne, Prahran and Carlton often sit on clay-heavy soils that move significantly with moisture changes. Courtyards in these properties are often tight spaces with limited drainage options, brick walls on multiple sides, and architectural features that need to be respected. Cutting corners on the sub base in this kind of environment is asking for the paving to fail within a few years.

Where most paving projects go wrong

In our landscape construction work across Melbourne over the past 30 years, we see the same sub base problems repeatedly when called in to repair or replace failed paving installed by others.

Pavers laid on compacted sand or crushed rock alone. Cheaper, faster, and the most common cause of failure in residential paving. Works for a year or two, then starts moving.

No reinforcement in the slab, or reinforcement laid on the ground. A non-reinforced slab will crack. Reinforcement sitting on the ground does nothing because it's not embedded in the concrete.

No drainage falls. Surfaces poured dead flat hold water. Water sitting on the substrate eventually finds its way under or around the pavers, and that's where the movement starts.

Pavers laid before the slab has cured. Concrete needs time to reach proper strength. Laying on a green slab means the adhesive isn't bonding to fully cured concrete, and the joints between pavers can shift before the substrate has stabilised.

No allowance for thermal expansion. Larger paved areas need control joints or expansion joints to handle thermal movement. Without them, the slab and the paving above it crack along stress lines.

None of these failures are visible on day one. They show up at the two-to-five-year mark, which is well past the point where most warranties have expired and the original installer is no longer around to fix them.

What proper landscape construction looks like in practice

CHS has been building landscapes across Melbourne since 1995, and our approach to landscape construction follows the same principle on every job: spend time on the parts of the project nobody will see, because that's what determines how long the finished result lasts.

For a typical premium courtyard paving job, this means:

  • Engineering input on slab thickness, reinforcement spec, and drainage design where the project warrants it
  • Proper formwork built to actual finished levels, not eyeballed
  • Reinforcement positioned correctly within the slab using bar chairs at appropriate spacing
  • Clean concrete pour with attention to falls, finish, and curing time
  • Dry-lay of pavers before final fixing, especially for ashlar patterns or anything that needs a specific layout
  • Pavers fixed on adhesive once the slab is fully cured, with proper joint widths and consistent levels

The same principles apply to larger landscape construction projects. Our earthmoving and transport capabilities, including GPS-controlled dozer and excavator work, mean we can prepare commercial-scale paving and hardstand bases to the same standards as a small residential courtyard. The technology changes, the scale changes, the principle doesn't.

What to ask when you're getting paving quotes

If you're getting quotes for a paving project, the answers to a few specific questions will tell you a lot about what you're actually paying for.

What's going under the pavers? If the answer is "compacted sand" or "crushed rock" for a premium residential project, that's a red flag. For most courtyard paving in inner Melbourne, the right answer involves a reinforced concrete slab.

How thick is the slab and how is it reinforced? A vague answer here suggests the contractor either doesn't know or hasn't thought about it. A confident answer should reference slab thickness in millimetres, reinforcement mesh type, and bar chair spacing.

What are the drainage falls? Any paved area needs falls. If the answer is "we'll just slope it a bit" rather than a specific percentage gradient toward defined drainage points, the drainage hasn't been designed properly.

How long will the slab cure before pavers go down? Concrete reaches usable strength in around seven days and full strength in twenty-eight. Quality work waits. Rushed work doesn't.

Will you dry-lay the pavers before fixing? Especially relevant for ashlar patterns, irregular materials, or anything where the layout matters. Dry-laying is the only way to guarantee the pattern works before the adhesive goes down.

The contractor who answers these questions clearly and specifically is the contractor who's done the work properly enough times to have learned what matters.

The long view

Premium paving isn't cheap. A properly built courtyard with quality limestone, bluestone or natural stone pavers on a reinforced concrete slab represents a serious investment. The difference between paving that holds up for decades and paving that needs replacing within five years isn't the stone itself. It's everything underneath.

Sub base preparation is the most important part of any paving project in Melbourne, and it's the part you'll never see once the job is finished. That's exactly why it matters most.

If you're planning a paving project, a courtyard build, or any other landscape construction work across Melbourne, get in touch to talk through the specifics.

Backyard stairway under construction with black retaining walls beside a wooden fence and house wall
19 August 2026
Anyone who has looked into garden steps in Melbourne for a narrow side passage knows the problem before the quote even lands. Most standard step solutions are designed for open garden beds with room to move, not a tight run between a boundary fence and the side of a house. When a block has a real change of level and next to no width to work with, the usual approach needs rethinking. That was exactly the situation on a recent job, a side access running down the length of a Melbourne home with a decent slope from front to back. The fix was a set of steel stair units, slim structural frames that hold the shape of the steps before anything else goes in on top. Why side access is its own problem Melbourne's inner and middle suburbs are full of period homes built long before anyone thought about side access as a design problem. Narrow gaps between the house and the boundary fence were left over space, not planned circulation. Somewhere down the track, that gap usually ends up as the main route to a garden shed, a bin store, a side gate, or the back garden itself. Add a natural fall in the block, which is common across large parts of Melbourne, and that narrow strip suddenly needs to manage a change of level as well as foot traffic. There is rarely room to spread a gentle ramp or a wide set of steps across the width available. Whatever goes in has to do its job in a fraction of the space a step in an open garden would use. This is where a lot of standard landscaping approaches run into trouble. A generously proportioned set of garden steps looks fine on paper, but in a passage that might only be 800mm to a metre wide, there simply is not room for a bulky structure on either side of the tread. Why steel stair units solve it The answer on this job was a series of steel stair units, welded steel frames set into the slope to form the risers and hold the structure of each step. Rather than pouring a full concrete stringer or building a masonry structure to support the steps, the steel frame does the structural work in a much slimmer profile. Poured concrete versus a steel frame A poured concrete step structure needs formwork, curing time, and enough width either side to build and finish it properly. In an open part of a garden that is rarely an issue. In a side access hemmed in by a fence on one side and a house wall on the other, it can eat into space that was never generous to begin with. A steel stair unit does the same structural job, holding soil and fill in place and defining the shape of each step, but it arrives pre-formed and goes into the ground far closer to the boundary than a poured structure could safely sit. For a narrow side access, that difference in footprint can be the difference between steps that fit comfortably and a passage that feels tighter than it did before the work started. Structure first, finish later What is visible in a job like this partway through is just the steel frame, sitting in raw soil with no surface finish yet. That is deliberate. The frame is the structural stage, get this right and everything that follows, backfill, base preparation and the finished tread surface, has something solid and correctly shaped to sit on. It is not the most photogenic stage of a landscape construction job. There is no paving, no planting, nothing that looks finished. But it is the stage that decides whether the steps sitting on top in a few months' time stay solid or start to shift, crack, or settle unevenly within a couple of years. What happens after the frame goes in Once the steel units are set and levelled, the next stages are backfilling behind and within each riser, compacting that fill properly, and building up a base ready for the finished tread. Depending on the brief, that tread might be paving to match the rest of the property, exposed aggregate, or another hard-wearing surface suited to a side access that gets regular foot traffic. Because the steel frame has already set the shape and pitch of the steps, this later stage is mostly about getting the base and finish right rather than fighting the structure itself. It also means changes to material or finish further down the track do not require touching the structural steps underneath. Drainage behind the steps matters just as much A narrow side access is often the path water takes off a roof, a driveway, or higher ground at the front of a block, especially once a fall has been built into it deliberately, as steps require. Water sitting against the back of a step structure, steel or otherwise, is one of the more common reasons steps in tight side passages fail early. Getting drainage right behind and beneath the steps, so water is directed away rather than pooling against the structure, is part of the same stage as backfilling and base preparation. It rarely gets a mention in a finished photo, but it is one of the details that separates steps built to last from steps that need attention again within a few wet Melbourne winters. Where garden steps fit into landscape construction A job like this rarely happens in isolation. Side access steps are usually one part of a broader landscape construction scope, connecting a driveway or street frontage to a rear garden, a pool area, or a renovated outdoor living space. Getting the structural stages right, steps included, is what the rest of a landscape construction project gets built on. It also overlaps with paving and hardscaping , since the finished tread on a set of garden steps needs to tie into whatever paving material runs through the rest of the property. Matching material, falls and finishes across steps and paving is what makes a side access feel like part of the property rather than an afterthought squeezed down the side of it. Timing also matters more than most homeowners expect. Structural work like a steel stair unit install is best done while a side access is already stripped back for a broader landscape construction or renovation project, rather than as a standalone retrofit once paving, planting and fencing are all finished and in the way. Where the two can be planned together, the steps end up better integrated and the job as a whole runs more efficiently. Getting it right the first time Steps in a high traffic side access take a beating over the years, weather, foot traffic, bikes and bins included. A structure that is undersized, poorly supported, or built without proper drainage behind it tends to show that wear early, with cracking, movement, or pooling water at the base. Starting with a proper structural frame, whether that is a steel stair unit or another engineered solution suited to the site, is what avoids that outcome. It costs more attention at a stage nobody will ever see finished, but it is exactly the kind of groundwork that keeps a side access looking and functioning the way it should for decades rather than years. Frequently asked questions Do all garden steps need a steel frame like this? No. A steel stair unit is one option among several for building garden steps, and it tends to suit tight, narrow sites where a poured concrete or masonry structure would take up too much space. Open garden areas with more room to work in often suit other structural approaches just as well. Can steel stair units be used on a sloped side access with existing fencing and services? Yes, that is a common scenario. Steel units are set into the slope in stages and can be positioned to work around existing fence lines, drainage points and other services already running through a side access, which is part of why they suit constrained sites. What happens to the raw steel frame, is it visible in the finished result? No. Once backfill, base preparation and the finished tread are complete, the steel structure is concealed beneath the surface. What is visible afterwards is the finished step, whether that is paving, aggregate or another chosen material. If a narrow side access at your own property has an awkward change of level, it is worth having someone look at the structural options before locking in a finish. Get in touch with the CHS team to talk through what a site like yours would need.
Cab view of an excavator loading gravel into a black dump trailer on a rocky construction site
14 August 2026
Ask most people how you move dirt off a site faster and they'll point at the truck. Get a bigger one, do fewer trips. On real earthmoving jobs around Melbourne, though, the bigger gains often come from how the material is carted, not just how much fits in the tray. Efficient spoil removal is one of the quiet levers that keeps a bulk earthworks program on time, and the trailer doing the carting has a lot to do with it. The photo above shows exactly that: one of our excavators loading a side tipper on a growth-corridor site, ready to run spoil off site without the stop-start of a conventional setup. What the photo shows It's a straightforward loading shot with a lot going on underneath it. An excavator sits over a side tipper trailer, dropping bucket loads of excavated material in ready to cart away. The site is a growth-corridor development on Melbourne's fringe, the kind of open, high-volume job where a lot of soil has to leave the ground before levels are right and the build can move on. The interesting part is the trailer. It's a side tipper, and on a job like this it does something a standard truck and dog can't. The hidden cost of stop-start cartage On a bulk earthworks job, the excavator loading spoil is rarely the bottleneck. The bottleneck is the cart: how quickly each truck can take a load, get it off site, empty, and come back for the next one. Any dead time in that loop multiplies across a full day and a full fleet. A conventional truck and dog carries plenty, but to empty it the driver has to stop, raise the body, wait for the load to slide out, lower it again and move off. Each of those tips is a pause. On a tight or busy site, trucks can end up queuing to tip, and while they wait, nothing is being carted. That's time the machines are running and the clock is ticking, with no material actually leaving the site. How a side tipper changes the maths Tipping on the move A side tipper empties differently. Instead of coming to a stop and lifting the whole body, it discharges the load out to the side, and it can do it while still rolling. There's no need to halt, tip and reset before the next run. The load goes out, the trailer keeps moving, and the truck is straight back into the cycle. Take the stopping out of the tip and you take a chunk of dead time out of every single load. Over a day of continuous cartage, that's the difference between a site that keeps flowing and one that spends half its time waiting on trucks. Fewer idle machine hours Faster turnaround on the cart does more than move dirt quicker. It keeps the excavator working instead of sitting with a full bucket and nowhere to put it. On earthmoving jobs, idle machine hours are pure cost: fuel, operator time and hire all ticking over while nothing productive happens. Tighten the cartage loop and the whole site runs leaner. Where side tippers earn their keep around Melbourne Not every job needs one. For a small residential cut, a more compact setup makes better sense. Side tippers come into their own where there's real volume and room to work. That describes a lot of what's happening on Melbourne's edges right now. Growth-corridor suburbs to the north and south-east are in constant build mode, with subdivisions, civil works and commercial sites all shifting large quantities of material. On those jobs, spoil removal is often the pace-setter, and an efficient cart method pays for itself over the life of the works. It's the same thinking whether it's a subdivision, a commercial pad or a civil earthworks program. You can see the range of civil and earthmoving work we take on across our projects , from open growth-corridor sites to tighter established suburbs. The cart is part of the earthworks, not an afterthought There's a habit of treating spoil removal as the boring bit at the end, something to sort out once the digging is under way. On a well-run job it's planned from the start. How much material is leaving, where it's going, what gear carts it and how the trucks flow in and out of the site all get worked out before the first bucket comes out of the ground. That's where running the earthmoving and the transport together matters. When the same team scopes the excavation and the cartage, the two are matched to each other rather than bolted together on the day: the right trailer for the volume, the right number of trucks for the cycle, and a loading setup that keeps everything moving. Our earthmoving and transport work is built around that kind of coordination, so the material coming out of the ground has somewhere to go without holding up the dig. Planning spoil removal on a Melbourne earthworks job If you're pricing or planning a job with a lot of material to move, it's worth thinking about the cart as early as the dig. The volume of spoil, site access, where it can be tipped and the gear used to move it all shape how long the job takes and what it costs. Get that right and a big earthworks program stays on schedule. Get it wrong and the machines end up waiting on trucks. CHS has run earthmoving and civil earthworks across Melbourne for over 30 years, alongside the landscaping and horticultural side of the business. If you've got a site with spoil to shift, get in touch for a free quote and we'll take a look at what it needs. Frequently Asked Questions What is a side tipper and how is it different from a truck and dog? A side tipper is a trailer that empties its load out to the side rather than lifting the whole body to tip from the rear. The main practical difference is that it can discharge while moving, so it doesn't have to stop, raise and reset to empty the way a truck and dog does. On high-volume cartage that removes a lot of dead time from each load. Why does spoil removal affect how long an earthworks job takes? On bulk earthworks the excavation is often faster than the cart. If trucks are slow to turn around or end up queuing to tip, the machines can be left waiting with nowhere to put the material. Efficient spoil removal keeps the excavator working and the site flowing, which is usually what sets the overall pace. Do you only use side tippers on large sites? No. The right cart method depends on the job. Side tippers suit high-volume work with room to operate, such as subdivisions and growth-corridor sites, while smaller or tighter jobs are often better served by other gear. Matching the method to the volume and the access is part of scoping the work. Do you handle earthmoving across Melbourne's growth corridors? Yes. We regularly work on growth-corridor and civil sites around Melbourne, as well as established inner and eastern suburbs. Large-volume earthmoving and spoil cartage is a core part of what we do alongside the garden and landscape side of the business. Can CHS manage both the excavation and the spoil cartage? Yes. Running the earthmoving and the transport together means the dig and the cart are planned as one job, so the material has somewhere to go without holding up the excavation. It's generally more efficient than treating the two as separate trades.
Yellow dump truck spreading dark material on a dirt road site
3 August 2026
Some of the most important civil earthworks in Melbourne happen before anything is built, and you would struggle to tell by looking. On a recent commercial site, the CHS team was preparing ground for a future wetland. The soil looked firm and workable. The problem was what it does the moment water touches it. This was sodic soil: dispersive, erosion-prone, and the kind of ground that quietly undoes a project if it is not dealt with early. Treating it is a specialised part of civil earthworks, and it is a good example of why the groundwork stage matters more than the parts people notice later. What "dispersive" and "sodic" actually mean Most soil holds together when it gets wet. You can dig it, shape it, run water across it, and it stays roughly where you put it. Sodic soil does not behave that way. Sodic soil has a high proportion of sodium sitting on the clay particles, and that sodium stops the clay from binding together. So when water hits it, the clay disperses, the structure collapses, and the soil effectively washes away as a muddy suspension rather than staying put. That is what dispersive means: the soil comes apart in water instead of holding its shape. On a dry day it can look completely stable. Add rain or runoff and it starts to erode, form channels, and shift. Left untreated on a site that is going to hold water, that is a serious problem. Why it matters more on a wetland site A wetland is designed to move and hold water. That is the whole point of it, which means the soil underneath and around it is going to be wet, often, and for long stretches. Build that on dispersive sodic soil without treating it first and you get erosion, sediment washing into the water, banks that slump, and a site that never settles into its intended shape. The design might be perfect on paper. The ground decides whether it actually works. Treating the soil: stabilising dispersive ground The fix for sodic soil is to change how the soil particles behave, so the clay binds together instead of dispersing. In civil and agricultural earthworks, that is typically done by working a calcium-based amendment such as gypsum through the soil. The calcium displaces the sodium, the clay structure holds together again, and the ground becomes far more stable when wet. The detail that matters is doing it thoroughly and at the right stage. Treatment has to be worked through the soil properly, not just spread on top, and it has to happen before the site is shaped and exposed to water. Get the timing and the coverage right and dispersive ground can be turned into a stable, workable base. The specifics of any given site's treatment come down to what that ground actually needs, because soil varies across a project and the right approach comes from testing and assessing it rather than a one-size formula. Shaping the site so water works with it Treating the soil is one half. Managing where the water goes is the other. Part of preparing a site like this is grading and shaping it so runoff moves in a controlled way rather than pooling or cutting its own paths. Good site preparation anticipates how water will move once the wetland is functioning, and once Melbourne's wetter months arrive, and shapes the ground so that movement is planned rather than accidental. This is standard civil earthworks discipline, the same thinking that goes into drainage and levels on any earthmoving job. Water always wins eventually, so the job is to decide where it goes before it decides for you. Why this is civil earthworks, not just moving dirt There is a view that earthmoving is a blunt trade: dig here, push that there, load the truck. Site preparation like this is the opposite. It relies on reading ground conditions, understanding how different soils behave, and knowing what has to happen, in what order, for the finished site to hold up. That is the civil earthworks side of CHS. Alongside the garden and landscape work the business is known for, the team runs earthmoving and site preparation across Melbourne, from residential builds to commercial and growth-corridor developments. The common thread with the horticultural side is the same one that runs through this whole job: the groundwork done properly at the start is what makes everything after it work. Where wetland and environmental work fits in Growth corridors and new developments across Melbourne increasingly include wetlands, retention basins, and landscaped drainage as part of the plan. These are not decorative extras. They manage stormwater, support planting, and handle runoff for whole developments. Preparing the ground for them, treating problem soils, controlling erosion and shaping levels, is specialised civil work that sits right at the intersection of earthmoving and horticulture. That happens to be exactly where CHS has worked for three decades, and it is part of the broader specialised services the team takes on. Some of that larger commercial work is captured on the projects page . The takeaway: the ground decides the result It is easy to judge a finished site by what is on top: the water, the planting, the shaped banks. But whether all of that lasts is decided much earlier, by how well the soil underneath was understood and treated. Dispersive sodic soil is a good reminder of that. Ignore it and it erodes the project from below. Treat it properly, at the right stage, and it becomes a stable foundation you never have to think about again. That is the quiet, unglamorous heart of good civil earthworks. Planning civil earthworks or site preparation in Melbourne? Whether it is a commercial development, a wetland or drainage project, or a residential build that needs the groundwork done right, the soil and site preparation stage is where the result is won or lost. CHS has handled civil earthworks and site preparation across Melbourne since 1995, alongside the horticultural and landscaping side most earthmoving outfits do not offer. Get in touch for a free quote and we will take a look at what your site needs. Frequently Asked Questions What is sodic soil and why is it a problem? Sodic soil has a high level of sodium attached to its clay particles, which stops the clay binding together. When it gets wet the structure breaks down and the soil disperses and erodes, even though it can look completely stable when dry. On any site that will hold or move water, that makes it prone to erosion and instability unless it is treated first. What does dispersive soil mean in earthworks? Dispersive soil comes apart in water rather than holding its shape. Instead of staying put when runoff crosses it, the particles separate and wash away as a muddy suspension. It is a common issue on some Melbourne sites and needs to be identified and managed during the earthworks stage. How do you treat sodic or dispersive soil? The usual approach is to work a calcium-based amendment such as gypsum through the soil, which helps the clay bind together again instead of dispersing. The treatment needs to be mixed through properly and carried out before the site is shaped and exposed to water. The exact method depends on the specific soil, so it is guided by assessing the ground rather than a fixed formula. Why does soil treatment matter for a wetland? A wetland is designed to hold and move water, so the surrounding soil spends a lot of time wet. If that soil is dispersive and untreated, it erodes, sediment washes into the water, and banks slump. Treating and stabilising the ground first is what lets the finished wetland hold its shape and function as intended. Does CHS do commercial and civil earthworks in Melbourne? Yes. Alongside garden maintenance and landscaping, CHS runs earthmoving, site preparation and civil earthworks across Melbourne, including commercial and growth-corridor projects. This mix of horticultural and civil capability is unusual, and it suits projects like wetlands where the two overlap.
Orange underground storage tank in a construction trench, with warning flags and mud around it
29 July 2026
Some jobs look small on the run sheet and turn into a full day. This one was the opposite. Out on a construction site in Craigieburn, in Melbourne's northern growth corridor, an underground water storage tank went from a marked-out patch of dirt to a tank sitting level in the ground and ready for concrete backfill, all inside about four hours. Broke ground in the morning, done by lunch. It's the kind of result that only happens when the excavation and the tank placement are handled by the same crew, in one continuous sequence, rather than waiting on separate trades to turn up. Here's a look at what actually goes into an install like this, and why underground water storage is showing up more and more on new builds across Melbourne's north. Why go underground with water storage? Above-ground tanks are simple, but they cost you space and they're not always what a site can accommodate. On a tight residential block, a commercial development, or a growth-corridor build where every square metre is spoken for, an underground tank stores the same water without eating into usable land. Once the tank is set into the excavation and the surround is backfilled, the ground above it can be reinstated. Depending on the site, that means it can be paved over, planted out, driven on, or built near. The storage sits out of sight and out of the way, doing its job through the dry months when Melbourne water is worth holding onto. That's part of why we're seeing steady demand for it across the northern corridor. Suburbs like Craigieburn, Mickleham and Donnybrook are in constant build mode, and underground water storage suits new sites where the groundworks are already open and it makes sense to get the tank in while the machines are there. The install: four hours, one crew The speed on this job wasn't luck. It came down to sequencing the work so nothing sat waiting. First, the excavation. The trench has to be dug to the right depth and dimensions for the specific tank, with enough clearance around it to backfill evenly. Too tight and you can't get an even surround; too loose and you're moving more material than you need to. This is where having earthmoving gear and operators on the same team pays off. The hole is dug to suit the tank, not to whatever's roughly close enough. Then the base. The tank has to sit level and fully supported across its footprint, so the bottom of the excavation is prepared before the tank goes anywhere near it. A poly tank that isn't evenly bedded will carry uneven load once it's backfilled and filled with water, and that's exactly the kind of shortcut that causes problems years later. Then placement. The tank is set into the prepared trench, checked for level, and connected up. In the photo you can see it strapped and positioned, sitting square in the cut with the flagged site barriers around it. Finally, it's readied for concrete backfill. Underground poly tanks are backfilled with a concrete surround rather than just soil, because the concrete braces the tank walls against ground pressure and stops the tank shifting or deforming once it's loaded. Get that surround right and the tank is locked in for the long haul. That last stage is what the whole morning was building toward, and by lunch it was ready to pour. Why the civil side matters as much as the tank Anyone can drop a tank in a hole. The difference between an install that lasts and one that causes trouble is almost entirely in the groundwork around it, and that's civil work, not plumbing. The excavation depth, the base preparation, the evenness of the backfill, the way ground pressure is managed once the tank is loaded: all of it is earthmoving and site-preparation discipline. It's the same thinking that goes into footings and slabs on a construction job. When a business runs both the horticultural side and the civil side under one roof, a tank install doesn't get split across a digger operator who leaves once the hole is done and a separate crew who places the tank. One team scopes it, digs it, sets it and preps it. That's how a job like this gets finished in a morning instead of dragging across two site visits. CHS has run earthmoving and civil earthworks across Melbourne for over 30 years, alongside the garden and landscaping side of the business. Water storage sits right where those two capabilities meet, which is exactly why water storage and tank installation is one of the services we handle end to end. Water storage is only half the picture Storing water is one thing. Getting it to where it's needed, reliably and efficiently, is the other half. That's where storage links up with the wider water side of a property. On garden and landscape jobs, stored water often feeds into an irrigation system, whether that's a handful of drip lines through garden beds or a larger multi-valve setup across a whole property. Thinking about storage and supply together, rather than as two separate jobs, is what keeps the right amount of water in the right place at the right time. It's the same principle whether it's a suburban garden or a commercial site: plan the water system as a whole and it works; bolt bits on afterwards and you're forever chasing problems. Considering underground water storage in Melbourne? Whether it's a new build in the growth corridor, a commercial site, or a residential property where you'd rather not lose the space to an above-ground tank, underground water storage is worth looking at. The key is having the excavation, placement and backfill handled properly and in sequence, because that's what makes it fast to install and reliable for the long term. You can see more of the civil and landscaping work we do on our projects page , or get in touch for a free quote and we'll take a look at what your site needs. Frequently Asked Questions How long does it take to install an underground water tank? It depends on the tank size, the site access and the ground conditions, but a straightforward install can be dug, placed and readied for backfill in a single morning. On this Craigieburn job the tank went from breaking ground to ready-for-concrete in about four hours, largely because the same crew handled both the excavation and the tank placement in one continuous run. Why are underground poly tanks backfilled with concrete? A concrete surround braces the tank walls against the pressure of the surrounding ground and the weight of water once the tank is full. Backfilling with soil alone doesn't provide the same support, and can allow the tank to shift or deform over time. The concrete locks the tank in place and helps it hold its shape for the long term. Can you build or pave over an underground water tank? In most cases the ground above an underground tank can be reinstated once the install is complete, which is one of the main reasons people choose to go underground. What you can do above it depends on the tank, the depth and the site, so it's best assessed for the specific property rather than assumed. Do you install underground water tanks in Melbourne's growth corridors? Yes. We regularly work across Melbourne's northern growth corridor, including suburbs like Craigieburn, Mickleham and Donnybrook, as well as the inner and eastern suburbs. Underground water storage suits new-build sites particularly well, since the groundworks are already open and the tank can go in while the earthmoving gear is on site. Is a tank the same as an irrigation pump? No, they do different jobs. A storage tank holds water; an irrigation system pump boosts pressure to push that water through the lines and out to the garden or property. On many jobs the two work together, with stored water feeding an irrigation system, but they're separate parts of the setup.
Rectangular black pool cover in a concrete patio area, with white pipes and a small pink object at right
25 July 2026
Not every garden project starts with a blank patch of soil. This one started with an old pond that had reached the end of its useful life. Rather than fill it in and lose the space, the CHS team converted it into a raised planter box, built from the base up to drain freely, water evenly and keep whatever gets planted in it healthy for years. The part you can see in the photo is the part most people never notice: the groundwork that decides whether a planter thrives or slowly turns into a bog. Here is a look at what goes into a build like this, and why the irrigation and drainage sitting underneath matter far more than they get credit for. Drainage comes first, always Before a single plant goes in, the base has to manage water. The black matrix across the bottom of the planter is a drainage cell layer. These interlocking cells create a void beneath the soil so water can move down and away instead of pooling around the roots. Waterlogged soil is one of the most common reasons planters and raised beds fail. When soil stays saturated it starves the roots of oxygen, and root rot follows close behind. Build the drainage in from the start and the planter can handle heavy rain without drowning the plants. Skip it, and no amount of careful planting or watering will save the bed once the wet months arrive. This is where a planter box has more in common with proper landscape construction than with a bag of potting mix. The structure underneath does the long term work, the same principle CHS applies to footings, slabs and retaining walls on every build. Water in: a drip irrigation system built for the space With drainage sorted, the next job is getting water to the plants consistently. Running around the perimeter of this planter is a drip irrigation system, and for a bed like this it is exactly the right tool. A drip irrigation system delivers water slowly and directly to the root zone through a network of lines and small emitters. Instead of spraying water across the surface and losing much of it to wind and evaporation, a drip or trickle irrigation system puts water precisely where the plants need it, at a rate the soil can actually absorb. For garden beds, planters and hedging, that means healthier plants, less waste and far less hand watering. It is also why a drip irrigation system suits Melbourne gardens so well. Our summers are hot and dry enough that inconsistent watering shows quickly, and water is worth using efficiently. A well designed garden irrigation system takes the guesswork out of it and keeps everything on a steady schedule, whether it is a single planter, a run of garden beds or a full lawn irrigation system across a property. If you want to see the scope of what that can involve, our irrigation installation and maintenance work ranges from simple single valve setups right through to systems running sixty valves or more. Water out: the sump pump, and why pumps matter in irrigation Getting water to the plants is only half the story. This build also includes a sump pump to clear excess water after heavy rainfall. The drainage cells move water off the root zone, and the sump pump lifts it up and out so it never sits and stagnates at the base. It is worth clearing up a common mix-up here. A sump pump and an irrigation system pump do two very different jobs. A sump pump removes unwanted water. An irrigation system pump does the opposite, boosting pressure to push water through the lines where mains pressure alone will not do the job, which is common on larger properties or on systems running many valves and zones. On this planter, both directions of water management are handled: consistent supply through the drip lines, and reliable removal through the sump. Managing water from both directions is what keeps a reused feature like this performing. It sits alongside the broader thinking that goes into water storage and supply on a property, where the goal is always to keep the right amount of water in the right place at the right time. It is the difference between a planter that looks the part on day one and one that actually lasts. Why building it in from the start pays off The reason this planter will work is that the irrigation and drainage were designed into the build, not bolted on afterwards. Retrofitting drainage into a finished bed is disruptive and expensive. Adding irrigation once a bed is fully planted means working around established roots. Doing both from the base up, while the structure is open, is cleaner, cheaper over the life of the bed and far more reliable. That integrated approach, combining landscape construction, irrigation and drainage in a single job, is well suited to Melbourne properties where reworking an existing feature is often more practical than starting from scratch. An old pond, a tired water feature, a raised bed that never drained properly: all of them can be rebuilt into something that works, provided the groundwork is done right. Once it is planted up and running, a bed like this asks for very little beyond regular garden maintenance to keep it looking its best, because the hard part was solved underground before the soil ever went in. Frequently Asked Questions What is a drip irrigation system and how does it work? A drip irrigation system delivers water slowly and directly to the root zone through a network of lines and small emitters. Rather than spraying water across the surface, it releases it at a rate the soil can absorb, which reduces evaporation and waste and keeps plants evenly watered. It suits garden beds, planters, hedging and pots particularly well. Is a drip irrigation system better than sprinklers for garden beds? For garden beds and planters, usually yes. A drip or trickle irrigation system targets the root zone with very little waste, whereas sprinklers lose more water to wind and evaporation and can wet foliage in ways that encourage disease. Sprinklers still have their place across open lawns, but for beds and planters a drip system is generally more efficient and more effective. Why does a planter box need drainage if it already has irrigation? Because irrigation and drainage solve opposite problems. Irrigation supplies water, drainage removes the excess. Without proper drainage, water from rain or over watering has nowhere to go, the soil stays saturated, and the roots suffocate. A drainage cell base, and where needed a sump pump, keeps water moving through the bed so the plants get what they need without sitting in it. Do I need a pump for my irrigation system? Not always. Many garden irrigation systems run perfectly well on mains pressure. An irrigation system pump becomes useful on larger properties, on systems with many zones or valves, or where mains pressure is too low to run everything reliably. It is best answered by looking at the specific property and how the system needs to perform. Can an old pond or water feature be converted into a garden bed? Yes. An old pond or disused water feature can be converted into a planter box or raised garden bed, provided the drainage and irrigation are rebuilt to suit its new purpose. The existing structure often gives you a head start. The key is getting the base, the drainage and the watering right before any soil or planting goes in. Rework a tired feature into a garden that lasts Thinking about a drip irrigation system, a new garden bed, or converting a pond or worn out feature into something that actually works? CHS has designed and installed irrigation and built gardens across Melbourne since 1995, blending council grade horticultural knowledge with the civil and construction side most gardening companies do not offer. Get in touch for a free quote and we can have a look at what your space needs.
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