If you’re planning a home renovation, here’s the statistic that should keep you honest: the average Australian renovation goes 20-40% over budget.

That’s not because homeowners are bad planners. It’s because the renovation industry is structured in ways that make cost blowouts almost inevitable unless you know what to watch for.

Mistake #1: Not Getting Multiple Quotes

This seems obvious, but an alarming number of people get one quote and accept it. Or they get three quotes and pick the cheapest without understanding why it’s cheapest.

Get at least three quotes for any significant work. Compare them item by item, not just the total. The cheapest quote might exclude things the others include (permits, waste removal, site cleanup).

Ask each contractor to explain their quote in detail. If they can’t or won’t, that tells you something about how they’ll communicate during the project.

Mistake #2: Underestimating the Timeline

Your contractor says eight weeks. Plan for twelve. Not because contractors are dishonest (though some are), but because renovations involve dependencies that create cascading delays.

The plumber can’t come until the framing is done. The framing can’t be inspected until the inspector is available. The inspector has a three-week wait time. Now your eight-week project is eleven weeks.

Materials delays compound this. If you’ve chosen a specific tile that’s back-ordered for six weeks, the entire project pauses.

Build flexibility into your timeline and don’t plan anything (holidays, events, moving in) that depends on the renovation finishing on time.

Mistake #3: Changing Your Mind Mid-Project

Changes during construction are the number one cause of budget blowouts. Moving a wall, adding a window, upgrading fixtures mid-build is enormously expensive because work may need to be undone and redone.

Make your decisions before construction starts. All of them. Tiles, fixtures, colours, layout. Lock these in and don’t change them unless absolutely necessary.

Visit display centres and showrooms during the planning phase. Order samples. Make physical selections, not just decisions based on pictures.

Mistake #4: Skipping the Contingency Budget

Professional project managers plan for 10-15% contingency on construction projects. Homeowners should do the same.

If your renovation budget is $100,000, set aside $15,000 for unexpected issues. Structural problems behind walls. Electrical wiring that doesn’t meet current code. Asbestos discovery in older homes.

These aren’t unlikely events. In Australian homes built before 1990, encountering unexpected issues during renovation is more common than not.

Mistake #5: DIY Where You Shouldn’t

Painting? Sure. Tiling a small bathroom? Maybe, if you’re handy. Electrical work? Absolutely not.

In Australia, electrical and plumbing work must be done by licensed professionals. It’s not just a quality issue — it’s a legal and insurance issue. Unlicensed work can void your home insurance and create safety hazards.

Even for work that doesn’t require licensing, be honest about your skills. Poor DIY tiling or carpentry costs more to fix than getting a professional to do it right the first time.

Mistake #6: Ignoring Council Approvals

Some renovations require development approval from your local council. Building beyond the existing footprint, changing rooflines, and adding a granny flat typically require approval.

Starting work without required approvals can result in fines, being forced to remove the work, or problems when you sell the property.

Check with your local council early in the planning phase. The approval process can take weeks or months, and it’s better to know that upfront than to discover it after construction was supposed to start.

Mistake #7: Not Checking Contractor Credentials

In Australia, builders need to be licensed. Check your state’s building licensing register. Ask for their licence number and verify it.

Check if they’re insured. Home warranty insurance is required in most states for residential work above a certain value. This protects you if the contractor goes out of business or the work is defective.

Ask for references and actually call them. Visit completed projects if possible. A good contractor welcomes this. A bad one makes excuses.

Mistake #8: Prioritising Aesthetics Over Function

The beautiful kitchen with the marble benchtop and brass fixtures is lovely. But does it have enough storage? Is the layout practical for actual cooking? Are the materials durable enough for daily use?

Prioritise how the space works, then make it look good. A functional space with modest finishes is better than a beautiful space that doesn’t meet your daily needs.

The Renovation That Works

The successful renovations I’ve seen share common traits: thorough planning, realistic budgets with contingency, decisions made before work starts, and a good contractor with verified credentials.

Take more time planning. Spend less time on Pinterest and more time on building specifications. Get your decisions locked in early.

Renovations should improve your home, not your stress levels. Preparation is the difference.