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House & Garden


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Thinking about renovating or extending an older home? Before you pick up a sledgehammer or call the builder, there’s one crucial step you shouldn’t skip: getting a pre-scan report.

It’s not the most glamorous part of the project, but for properties built before the 1980s—or even those a little younger—a pre-scan could save you serious money, stress, and structural headaches.

Whether you’re opening up a wall, pouring a new slab, or adding an upper level, here’s why pre-scan reports are essential when working with older properties.

What Is a Pre-Scan Report?

A pre-scan report (also known as a structural scan, ground-penetrating radar (GPR) scan, or concrete scan) is a non-invasive way to see what’s hiding behind or beneath the surfaces of your home—before work begins.

Depending on the type of scan, it can detect:

  • Hidden structural elements (steel reinforcements, beams, footings)

  • Live electrical cables and wiring

  • Plumbing and drainage lines

  • Asbestos-containing materials

  • Voids, defects, or subsurface movement


In short, it gives you a clearer picture of what’s really going on in your walls, floors, and slabs—so you’re not renovating blind.

Why It Matters More With Older Homes

Older homes—especially those built in the post-war era up to the 1970s—were constructed under different standards and materials than we use today. You’re more likely to come across:

  • Unmapped wiring or plumbing

  • Outdated or deteriorating materials

  • Asbestos in walls, eaves, or insulation

  • Brittle concrete or shifting foundations

  • Unreinforced structures not up to current load-bearing codes

Without a scan, you (or your builder) might be guessing what’s inside that wall or slab. And when guesswork meets power tools, things can go badly—fast.

Five Big Risks of Skipping a Pre-Scan

Here’s what can happen when you don’t scan before you start:

1. Hitting Live Wires or Pipes

Striking a live electrical cable or copper water line can lead to damage, flooding, fire risk, or personal injury—not to mention expensive emergency repairs.

2. Accidentally Weakening Structural Supports

Knocking down or cutting into a wall that contains key structural supports could cause the area to become unstable or unsafe.

3. Unexpected Asbestos

Asbestos is still common in older homes—especially in sheeting, insulation, vinyl tiles, and roofing. Disturbing it during renos can expose your family or trades to serious health risks.

4. Delays Due to Rework

If hidden issues are found mid-way through a job, your renovation can come to a grinding halt. That means new plans, approvals, and increased costs.

5. Compliance and Insurance Issues

Renovating without doing proper due diligence can lead to compliance issues with your local council—and if something goes wrong, your insurance may not cover the damage.

When Should You Get a Pre-Scan?

You don’t need to scan every single inch of the house. But if your renovation involves any of the following, a pre-scan is a smart move:

  • Removing or modifying internal or external walls

  • Drilling or cutting into concrete slabs

  • Installing new plumbing or electrical in existing structures

  • Digging near foundations or footings

  • Working in areas where asbestos may be present

Even if your builder or tradie hasn’t requested it, you’re well within your rights to ask for a pre-scan before major work starts. A reputable tradesperson will appreciate the forward planning.

What Does a Pre-Scan Involve?

Most pre-scan services are quick, clean, and don’t damage any surfaces. Depending on what’s being scanned, technicians may use:

  • Ground Penetrating Radar (GPR) – for concrete slabs, driveways, and underground utilities

  • Thermal Imaging – to detect moisture, leaks, or wiring inside walls

  • Fibre-Optic Cameras – for hard-to-access wall cavities or ducting

  • Asbestos Sampling (if needed) – carried out safely and according to regulations

After the scan, you’ll receive a clear report showing what was found, with photos or marked-up diagrams. This information can then be shared with your builder or architect to inform the construction plan. Consider using dial before you dig to find a local company who can complete a pre scan for you.

How Much Does It Cost?

Pre-scan pricing depends on the size of the area, the type of scan needed, and your location. However, most basic GPR scans start from a few hundred dollars—which is small change compared to the cost of fixing a burst pipe, electrical fault, or structural damage after the fact.

It’s a one-off cost that pays for itself in certainty, safety, and fewer surprises.

Do I Still Need a Builder or Engineer?

Yes. A pre-scan is a diagnostic tool—it doesn’t replace professional advice or certification. What it does do is give your builder, engineer, or architect the full picture so they can design and plan safely and confidently.

In some cases, your builder may even require a scan before cutting or core drilling, especially in concrete areas or older foundations.

Pre-Scan Reports Help Keep Everyone Safer

From DIY renovators to experienced trades, no one wants to damage what's hidden behind a surface. A scan offers clarity, reduces risk, and gives you peace of mind before the dust starts flying.

It’s not about adding red tape—it’s about working smarter.

Planning a Reno? Don’t Skip This Step

If your property was built before the 1990s, make a pre-scan part of your early planning. Whether you’re working with an architect, a builder, or managing things yourself, that early insight can save time, money, and a lot of unnecessary headaches.

Because while new benchtops and bi-fold doors are exciting, it’s the decisions behind the scenes—like a proper scan—that set your project up for long-term success.