Earthworks: setting out, excavation, cut and fill, compaction

Transferring the setting-out plan onto the ground with profiles and string lines, excavating to the right depth, and compacting fill in layers. Sand does not behave like clay, and uncompacted fill will find you out later.

⏱ 2 hAdvanced🔗 11 resources (10 free)

Setting out is where a drawing becomes physical marks you can dig to, and everything after inherits the accuracy of what you do today. Set the patio 40 mm too high and you find out when the paving reaches the threshold and sits above the damp proof course — which is not a paving fix, it is excavating a base you already paid for.

It is also the most dangerous work in this course. Perth sand has almost no cohesion: a trench face that looks stable at smoko can slab off without a sound, and a cubic metre of damp sand weighs somewhere around 1.5 tonnes. People are killed by trenches that were not particularly deep. On a renovation it is harder again, because you are cutting into ground that already holds services, old bases, root plates and forgotten fill.

Before anything moves: three checks that are not optional

These are legal obligations, not good practice.

Lodge a Before You Dig Australia enquiry. Free, online, plans emailed to you, and it covers private property. Do it before you book the machine — what comes back may change where you dig.
Check for a Water Corporation asset. Most Perth back yards have a sewer gravity line through them, and ground-disturbing works within 2 metres of one need approval under section 90 of the Water Services Act 2012. Water mains are 4 or 6 metres depending on diameter; structures are 10 metres.
Respect Western Power’s approach distances. 30 cm to low voltage underground cable when using power tools or plant, 50 cm to high voltage, 3 metres to transmission. Overhead is its own hazard — an excavator arm raised into a service line is a fatality, not an incident.

Never use a machine to find a service. Hand dig, approaching from the side, and work through locating services first if you have not already.

What a professional does at this stage

They set a datum before touching anything. One fixed, undisturbable point that will still exist when the site is a moonscape — a threshold, a step nosing, a mark on the house wall. Every level is then plus or minus from that point, never measured off the ground, because the ground is about to move.

They set profiles outside the work zone. Pegs inside the dig get knocked out on the first pass, and then nobody can prove where anything was.

They excavate to a calculated formation level, not to “about right”. Dig depth is finished level minus surface thickness minus bedding minus compacted sub-base, written down before the machine starts. Everything below ground gets covered by something expensive, and a base under-dug by 50 mm surfaces later as either a thin base or a high finished level.

Setting out: datum, profiles, then lines

Work from your levels and grading plan and the reduced levels recorded in levels, falls and datum.

Profiles are the tool: two pegs driven about a metre outside the corner of the work with a horizontal board screwed across them, set level at a known height above your datum and marked with a saw kerf where the string crosses. Two profiles define a line. The string represents either the finished level or a fixed offset above it — say 300 mm above, so you can dig underneath without touching it. Write that offset on the board.

Square the layout with a 3-4-5 triangle, using 3, 4 and 5 metres or better 6, 8 and 10, then check the diagonals of the rectangle are equal. A 900 mm builder’s square amplifies its own error over 8 metres.

Set falls now, not after excavating. 1:100 away from buildings is the usual minimum and Pavingexpert argues for 1:80 on block paving — over 7 metres, 1:80 is about 88 mm of fall, noticeably more than most people picture. Check with a 1200 mm level on a straight edge, not a short level.

How deep to dig

Work down from the finished surface. Two typical Perth build-ups:

Element	Patio (foot traffic)	Driveway (cars)
Paver	40 mm	60 mm
Bedding sand (compacted)	30 mm	30 mm
Compacted crushed limestone base	100 mm	150 mm
Excavate below finished level	170 mm	240 mm

Two corrections people forget. Base thickness is compacted thickness — loose limestone drops roughly 20 to 25% under a plate, so 100 mm compacted needs about 125 to 130 mm loose. And excavated sand bulks, so the pile is bigger than the hole when you order the bin. Confirm the clearance your wall construction needs below the damp proof course and weep holes before fixing any finished level against the house.

Cut, fill, and where it becomes an approval

Cut and fill balances on paper and never on site. In Perth you are usually in cut, because sand is easier to remove than to import and compact.

The line not to cross without checking: under clause 5.3.7 of the R-Codes, fill or excavation within 1 metre of a lot boundary, behind the street setback, must not be more than 0.5 metres above natural ground level at the boundary, and between the street boundary and the street setback the limit is 0.5 metres above or below. Above that, Table 4 wants a setback equal to the height and you are into a development application — see R-Codes and your council.

The moment a level change needs holding up you are building a retaining wall, which has its own permit trigger — commonly 500 mm of retained height, but confirm the figure with your council. Read retaining walls approval before you cut a batter you cannot leave.

Compaction: layers, water, passes

The rule is layers. Fill deeper than about 150 mm goes in as a series of layers, each compacted before the next is placed. Main Roads WA caps compacted layers at 450 mm in sand and 300 mm in cohesive material, but that assumes a roller — behind a hand-guided plate compactor, work in 150 to 200 mm lifts in sand and 100 to 150 mm in clay.

Water is not optional in sand. Dry Perth sand will not densify however long you stand on the plate; the grains just vibrate past each other. Main Roads allows Perth sands at 70–110% of optimum moisture content, a much wider band than the 90–110% for other materials. In practice, hose each layer until it is uniformly damp, not saturated. Sand that holds a squeezed shape is about right.

Three to four overlapping passes, each run overlapping the last by a third of the plate width, then one pass at 90 degrees to the first.

Sand versus clay

	Perth sand	Clay and clay-rich fill
Compacts by	Vibration	Impact and kneading
Right tool	Vibrating plate or roller	Rammer (jumping jack)
Moisture	Must be damp; will not compact dry	Narrow window; too wet and it shears and pumps
Compacted lift	150–200 mm	100–150 mm
Excavation face	Will not stand vertical	Stands up, then fails suddenly as a slab
Long-term risk	Settlement of uncompacted backfill	Shrink and swell with moisture

The most common failure on a renovation is service trench backfill. Someone runs conduit or retic pipe, pushes the spoil back in, stamps on it and paves over the top. Eighteen months later there is a dip following the exact line of the trench. Backfill every trench in compacted layers, even where nobody will ever see it.

Trenches: the part that kills people

An excavation 1.5 metres or more deep must be shored, benched or battered. Work in or near a trench deeper than 1.5 m is high risk construction work under the WHS Regulations, and any contractor doing it for you owes you a safe work method statement before they start.

For a domestic garden, stay well under that. If you need depth, batter the sides back rather than digging vertical — in loose sand that is a shallow slope, and assume a vertical face will not hold.

Keep spoil at least 600 mm from the edge, preferably 2 metres, and outside a 45-degree line up from the bottom of the trench. The spoil heap is a surcharge load, and so is a bobcat parked beside the trench.
Provide a ladder extending 900 mm above the surface, with access at intervals of no more than 30 metres.
Never enter a trench alone, and never enter one to “just grab” something.
Get out when it rains, and inspect before anyone re-enters.
Cutting limestone, pavers or concrete releases respirable crystalline silica. Cut wet or use on-tool extraction, and wear a fitted P2 respirator.

Heat, and working alone

Earthworks between December and March is the highest-exertion, lowest-shade work in the build, usually done by someone unacclimatised. WorkSafe WA’s figure is 250 ml of water every 15 to 20 minutes during hot work, and acclimatisation takes 7 to 14 days you will not have. Start at first light and stop by late morning. Heat exhaustion is clammy skin, nausea and a temperature up to 39°C; heat stroke is confusion, hot dry skin and above 40°C, and it is an ambulance. Working alone with a machine or in an excavation, tell someone and agree a check-in time.

Check levels as you go

After the strip. After the excavation. After every compacted layer. Not at the end. Check against the profiles and the datum, never against the surrounding ground, and photograph each layer before it is buried with a tape in shot.

What this feeds

You now have a site cut to formation level, compacted, with lines and levels fixed to profiles you can still read. That formation level is what everything else is built off — soakwell depths in drainage and soakwells, footings in retaining walls, and the sub-base itself in base preparation.

The next lesson covers the machinery that does most of this work — what to hire, what it can and cannot do on a Perth block, and how to get it through a 1-metre side gate without destroying the fence.

Checklist

Set profiles and string lines from your fixed reference points
Excavate to design depth allowing for sub-base and surface thickness
Compact fill in layers, not all at once
Check levels as you go, not at the end

Where to go deeper

Every link below was fetched and checked before it shipped. Nothing here is a guess.

Freegovernment60 minPerth / WA
Excavation: Code of practice
WorkSafe WA, Department of Energy, Mines, Industry Regulation and Safety
Why this oneThe regulator's own document on the one part of this lesson that can kill you, and it is specific rather than vague. It requires shoring or equivalent protection for any excavation 1.5 metres or more deep, caps the bottom vertical face of a bench at 1.2 metres, tells you to keep spoil at least 600 mm from the edge and preferably 2 metres, and to place it outside a 45-degree line drawn up from the bottom of the excavation. It also states plainly that mechanical equipment should never be used to locate a service and that hand digging must approach the service from the side.
Change this for Perth
Published 11 February 2014 and last updated 25 November 2024. It cites regulation numbers from the superseded Occupational Safety and Health Regulations 1996 (regulations 3.111 and 3.21); the current duties sit in the Work Health and Safety (General) Regulations 2022. The technical guidance is what WorkSafe still publishes and still expects, but do not quote the regulation numbers at anyone.
Link checked 2 Aug 2026
Freegovernment20 minPerth / WA
Safe work method statement for high risk construction work
WorkSafe WA
Why this oneThe page and its downloadable template are the fastest way to see what the WHS Regulations classify as high risk construction work. The template's tick-list includes 'work in or near a shaft or trench deeper than 1.5 m or a tunnel', 'work on or near pressurised gas mains or piping' and 'work on or near energised electrical installations or services' — three things a landscaping excavation routinely touches. If you engage anyone to do this work, a SWMS must exist before they start.
Change this for Perth
The SWMS duty binds a person conducting a business or undertaking, not a homeowner working on their own home. The list is still the best available checklist of what counts as genuinely dangerous work, and any contractor you hire owes you one.
Link checked 2 Aug 2026
Freetool10 min to lodgeAustralian
Before You Dig Australia
Before You Dig Australia
Why this oneFree, national, and the single step that separates a normal excavation from a very bad day. Register an account, draw your dig site on a map, submit, and the asset owners send plans to your inbox. It covers work on private property, not just roads and verges. Lodge it before you hire the machine, not on the morning it arrives.
Change this for Perth
BYDA returns plans from participating asset owners only. It will not show privately owned assets — the previous owner's shed power, an old bore line, an abandoned soakwell, unregistered poly. Those are your problem and they are found by hand digging and by your site analysis, not by BYDA.
Link checked 2 Aug 2026
Freegovernment10 minPerth / WA
Danger zones — working near our network
Western Power
Why this oneThe published minimum approach distances to underground cables, which is the number you need before a machine bucket goes anywhere near a verge or a meter box. Low voltage up to 1,000 V is 30 cm when using power tools or plant; high voltage from 1,000 V to 33 kV is 50 cm; anything above 33 kV is 3 metres and Western Power must assess any works inside that zone. Its companion excavation page directs you to Before You Dig Australia for the actual cable locations.
Link checked 2 Aug 2026
Freegovernment20 minPerth / WA
When to apply for approval for works near our assets
Water Corporation
Why this oneThe page most Perth renovators have never read, and the one that turns a back-yard sewer into a legal constraint. Under section 90 of the Water Services Act 2012, ground-disturbing works — excavation, earthworks, heavy vehicle movement — need approval within 2 metres of a sewer gravity pipeline or main drain, 4 metres of a water supply pipeline under 300 mm, and 6 metres of a water main 300 mm or larger. Structures such as sheds, pools and buildings trigger a much wider 10-metre zone, and trees and pile driving trigger 10 metres.
Change this for Perth
The distances are measured from the asset, not from the manhole lid you can see, so you need the actual alignment from your BYDA plans first. Applications tied to a residential building are lodged through BuilderNet rather than the general form.
Link checked 2 Aug 2026
Freestandard45 minPerth / WA
Specification 302 Earthworks
Main Roads Western Australia
Why this oneFree, current (revised 28 June 2024) and written specifically for Western Australian materials, which almost nothing else in this space is. It caps compacted layer thickness at 450 mm for sand and 300 mm for cohesive material, with a 100 mm minimum in both cases, and it publishes separate density targets for 'Perth Sands' — 95% for embankment construction and 96% for subgrade preparation. It also sets moisture at 70–110% of optimum for Perth sand against 90–110% for other materials, which is the numerical version of 'wet the sand and it will compact'.
Change this for Perth
This is a road specification written for smooth drum rollers and padfoot compactors. The layer thicknesses assume that plant. Behind a hand-guided plate compactor, halve them — 150 to 200 mm compacted lifts in sand is the realistic domestic equivalent.
Link checked 2 Aug 2026
Freegovernment20 min for clause 5.3.7Perth / WA
Residential Design Codes Volume 1 (Version 3, 10 April 2026)
Department of Planning, Lands and Heritage
Why this oneClause 5.3.7 Site works is the clause that decides whether your cut and fill is something you can just do or something you must apply for. Between the street boundary and the street setback line, retaining walls, fill and excavation are deemed-to-comply at not more than 0.5 metres above or below natural ground level. Behind the street setback and within 1 metre of a lot boundary, excavation or filling must not be more than 0.5 metres above natural ground level at the boundary. Beyond that, Table 4 sets a setback equal to the height — a 1.5-metre level change wants a 1.5-metre setback.
Change this for Perth
Version 3 dated 10 April 2026 — check you are reading the current version before you rely on a number. Local planning schemes and local development plans can vary these provisions, and failing deemed-to-comply is not illegal, it just means a development application and an assessment against the design principles.
Link checked 2 Aug 2026
Freearticle25 minOverseas — adapt it
Setting Out — Working Lines and Levels
Pavingexpert (AJ McCormack & Son)
Why this oneThe clearest free explanation anywhere of how to actually run a string line and transfer a level across a site: setting pins, the half-hitch knot that lets you slide a line up and down a pin, using a 1200 mm spirit level on a straight edge rather than a short one, sighting along a line with your eye at line level, and carrying levels around a curve with intermediate pins. It also works a gradient right through — 7 metres at 1:80 is about 88 mm of fall — which is the arithmetic most people get wrong.
Change this for Perth
British site. It sets its datum off the damp proof course and drains everything to gullies; in Perth you are far more likely to be falling to a soakwell or to a garden bed. Confirm the clearance your own wall construction needs below the DPC and weep holes before you fix a finished level, and treat its drainage-to-gully assumptions as a Perth soakwell problem instead.
Link checked 2 Aug 2026
Freearticle25 minOverseas — adapt it
Sub-bases
Pavingexpert (AJ McCormack & Son)
Why this oneThe layer rule stated plainly: 'Where a sub-base needs to be greater than 150mm in depth, it should be built-up as a series of layers, each being 150mm or less and thoroughly compacted before placing, levelling and compacting the next.' It also gives compacted thickness by duty — 75 mm for foot traffic, 100 mm for a domestic drive, 150 mm for cars and vans — which is the number you subtract when you calculate your dig depth.
Change this for Perth
It specifies DTp Type 1, a British graded aggregate that is not sold here. The Perth equivalent is compacted crushed limestone, which self-cements when laid damp and compacted in layers. Ignore any frost and freeze-thaw commentary entirely.
Link checked 2 Aug 2026
Paid · $167.11 AUD incl GST for a single-user PDFstandardAustralian
AS 3798-2007 Guidelines on earthworks for commercial and residential developments
Standards Australia
Why this oneThe Australian reference for how earthworks are specified, executed and tested on residential sites — site preparation, fill placement, compaction, subsoil drainage, retaining structures, slope stability and quality control, cross-referenced to the AS 1289 soil test methods. If a report, an engineer or a builder's specification on your job says 'compacted in accordance with AS 3798', this is the document they mean.
Change this for Perth
Written for developments large enough to employ a geotechnical testing regime, and priced accordingly. For a suburban garden the free Main Roads WA Specification 302 gives you the WA-specific layer thicknesses and Perth sand density targets without the cost — buy AS 3798 only if you are working to someone else's specification that names it, or check whether your local library offers Standards Australia reading-room access.
Link checked 2 Aug 2026
Freegovernment15 minPerth / WA
Working safely in hot conditions
WorkSafe WA
Why this oneEarthworks in a Perth summer is the highest-exertion, lowest-shade work in the whole build, usually done by someone unacclimatised. This gives the numbers: 250 ml of water every 15 to 20 minutes during hot work, 7 to 14 days to acclimatise and complete loss of acclimatisation after 4 weeks away from hot work. It separates heat exhaustion (body temperature to 39°C, clammy skin, nausea) from heat stroke (above 40°C, confusion, hot dry skin, convulsions), which is a medical emergency.
Link checked 2 Aug 2026

The rules, with sources

WA regulation changes. Each point below names its primary source and the date it was last checked — always confirm with your own council before you build.

Work in or near a shaft or trench deeper than 1.5 m, or a tunnel, is high risk construction work under the Work Health and Safety (General) Regulations 2022. A safe work method statement must be prepared before the work starts and kept accessible to every relevant worker.
WorkSafe WA ↗ · checked 2 Aug 2026
An excavation 1.5 metres or more deep must be protected by shoring or an equivalent system that prevents collapse. Excavated spoil should be kept at least 600 mm from the edge, preferably a minimum of 2 metres, and outside a 45-degree line drawn from the bottom of the excavation. Access and egress should be provided at intervals of no more than 30 metres, and a ladder must extend at least 900 mm above the surface.
Excavation: Code of practice, WorkSafe WA ↗ · checked 2 Aug 2026
Under section 90 of the Water Services Act 2012, approval is required before ground-disturbing works within 2 metres of a Water Corporation sewer gravity pipeline or main drain, 4 metres of a water supply pipeline under 300 mm, or 6 metres of a water supply pipeline 300 mm or larger. Structures such as buildings, pools and sheds trigger a 10-metre zone either side of the asset.
Water Corporation ↗ · checked 2 Aug 2026
Minimum approach distances to Western Power underground cables are 30 cm for low voltage up to 1,000 V when using power tools or plant, 50 cm for high voltage from 1,000 V to 33 kV, and 3 metres for transmission cables above 33 kV. Western Power must assess any works within 3 metres of a transmission cable.
Western Power ↗ · checked 2 Aug 2026
Under clause 5.3.7 of the Residential Design Codes Volume 1 (Version 3, 10 April 2026), retaining walls, fill and excavation between the street boundary and the street setback are deemed-to-comply at not more than 0.5 m above or below natural ground level. Behind the street setback line and within 1 m of a lot boundary, excavation or filling must not be more than 0.5 m above natural ground level at the boundary. Greater heights require a setback equal to the height under Table 4.
Department of Planning, Lands and Heritage ↗ · checked 2 Aug 2026
In the City of Melville, a building permit is required where a retaining wall retains soil exceeding 500 mm in height, including where tiered walls together retain more than 500 mm, and planning approval is required for walls more than 500 mm above natural ground level. The City also notes that the Building Act 2011 requires the adjoining landowner's consent where works affect their land. Confirm the equivalent figures with your own local government.
City of Melville ↗ · checked 2 Aug 2026