What’s Actually Under Your Backyard Before You Start Digging
A new fence, a retaining wall, a pool, a shed — none of it looks like a job that needs much thought before the first shovel hits the ground. But the ground itself is the part most homeowners get wrong. Underneath a typical Sydney backyard runs a tangle of electrical cable, gas line, water main, sewer connection, stormwater pipe and NBN infrastructure — and a fair amount of it was never put there with a future renovation in mind.
Hit the wrong thing and you’re not looking at an inconvenience. You’re looking at electric shock, a gas leak, a flooded trench, or a repair bill that dwarfs whatever you were planning to build in the first place. Here’s what actually needs to happen before you dig.
The backyard isn’t just dirt — it’s infrastructure
The assumption that underground services stay near the street is wrong more often than it’s right. Depending on when your home was built and how it’s been renovated since, your backyard could be carrying:
- Electrical cable
- Gas pipe
- Water main
- Sewer connection
- Stormwater pipe
- Telecommunications and NBN cable
- Irrigation lines
- Old building foundations from whatever stood there before
- Services nobody bothered to document at the time
None of this is visible. A lot of it was installed decades ago, moved during a renovation that predates the current owner, or never made it onto an official plan at all. That’s the real risk — not that services exist, but that nobody currently living in the house knows where.
Lodge a BYDA enquiry — but treat it as the start, not the finish
Before You Dig Australia (BYDA) is the free national portal for finding out what’s registered underground near your site. You mark out your dig area, utility owners get notified, and you get plans back showing roughly where their assets sit.
In NSW this isn’t optional courtesy — SafeWork NSW requires excavators to get current underground essential services information before work begins, particularly near gas and electricity assets. Skip this step and you’re not just risking a utility strike, you’re risking a breach.
What BYDA gives you is a starting reference, not a guarantee. The plans show what’s been registered — not necessarily what’s actually in the ground.
Why the plans you get back aren’t the full picture
This is the part that catches people out. A BYDA response tells you what utility owners have on file. It doesn’t tell you:
- The exact depth of anything
- Whether the asset has moved since the plan was drawn
- Anything that was installed without being registered
- Any private infrastructure inside your own boundary
Sydney Water is upfront about this on its own site — the plans you receive only cover the specific area you marked out, and they won’t reflect anything beyond that locked-in window. Renovations, landscaping and old repairs all shift things from where the original drawing says they should be. Treat every plan as approximate until you’ve confirmed it on the ground.
This is where a locator earns its fee
For anything beyond a shallow garden bed, a proper locate is worth arranging. Using electromagnetic locators and ground-penetrating radar, a locating specialist can trace and mark buried services directly on your site — including the ones that never made it onto a BYDA plan.
At Oz Detect, that’s the gap we fill between “here’s roughly where things might be” and “here’s exactly where to dig and where not to.” It’s a few hours of work that routinely saves homeowners from a five-figure mistake.
The services nobody tells you about: your own
Public infrastructure gets registered with BYDA. What you put in yourself doesn’t. Pool power supply, garden lighting circuits, irrigation, even a sewer line a previous owner rerouted without telling anyone — none of it shows up on a utility plan, because it’s private.
This is the blind spot in most excavation planning. People assume “I checked BYDA” means they’ve checked everything. It means they’ve checked the public stuff. A proper locating survey picks up both.
Check whether council needs to sign off first
Pools, retaining walls, granny flats, sheds, driveways and structural foundations often need council or certifier approval before you can break ground — separate from anything to do with utilities. Get this wrong and you’re looking at fines, stop-work orders, or having to undo what you’ve already built. If you’re not certain your project needs approval, ask your council before you start, not after.
Mark it, confirm it, then dig like you mean it
Once you know roughly where things are, mark the excavation zone clearly and have any detected services flagged or painted on the ground. From there:
- Verify locations again before the first cut — plans and markings can still be wrong
- Hand-dig near anything known to be close
- Stop immediately if you hit something unexpected
- Don’t fill in the gaps with assumptions
SafeWork NSW’s Excavation Work Code of Practice sets this out plainly: no excavation should proceed on assumption. If something turns up that wasn’t on the plan, the answer is to stop and investigate — not push through and hope.
What’s actually on the line
A struck utility isn’t just a repair invoice. It’s electric shock or electrocution, a gas leak, a burst water main, days without internet or phone service, an insurance claim that gets complicated fast, and possibly a regulatory issue on top of all of it. Weighed against that, the cost of getting a site properly located before you dig isn’t really a cost — it’s the cheapest part of the whole project.
Know what’s down there before you break ground
If you’re planning a backyard project anywhere in Sydney, find out what’s underneath before the digging starts. Oz Detect provides professional underground utility locating across Sydney and the surrounding area — for homeowners, builders, landscapers and contractors who’d rather know than guess.
Fence, retaining wall, pool, shed — whatever you’re building, we’ll help you dig with confidence and skip the costly surprise.
