Two Minutes at an Open Home Can Save You $100,000 on Foundations

There is one thing about a house you cannot fix cheaply. It is not the kitchen. It is not the bathroom. It is not even the roof.

It is the foundation.

A full restumping job on a standard Melbourne house starts at $30,000 and can blow past $100,000 if the subfloor requires underpinning 1. I have seen clients lose that kind of money because they skipped a two-minute check during an open inspection. Two minutes. That is all it takes to assess the most expensive component of any house.

I am going to walk you through the exact inspection routine I use when I visit properties for clients. You do not need a building inspector's licence. You need a torch, a willingness to get your knees dirty, and about 120 seconds.

Step one: walk the perimeter and look for access hatches

Before you go inside the house, walk around the outside. Look at the base of the external walls. Specifically, you are looking for two things.

First, small rectangular openings near ground level—typically 400mm by 500mm, covered with a grate or removable panel. These are subfloor ventilation openings. If you can see through them into the crawl space below the house, the building is on stumps. Most pre-1990s houses in Melbourne's southeast are raised on stumps rather than poured concrete slabs 2.

Second, look for a dedicated access hatch. This is usually a larger opening—big enough to fit your shoulders through—that was designed for maintenance access. If the house has one, this is your entry point.

A house with a good access hatch was built by someone who planned for maintenance. A house with no access hatch and sealed ventilation openings is harder to inspect and harder to repair. Not a deal-breaker, but it increases the cost of any future foundation work because tradespeople will need to create access.

Some houses have stumps but are set so low to the ground that you physically cannot get underneath. If the clearance between the ground and the bearers is less than 400mm, a restumping crew will need to excavate to work. Add $10,000-$15,000 to the bill.

Step two: open the hatch and use your nose

This is where most buyers lose their nerve. The access hatch is dark. It might be dirty. There could be spiders.

Get over it. You are about to spend $600,000 or more. A bit of dirt is the least of your worries.

Open the hatch and stick your head inside. Before you even look at anything, breathe in through your nose.

What are you smelling for? Moisture. A healthy subfloor smells like dry earth—dusty, neutral, slightly mineral. A problematic subfloor smells damp, musty, sometimes faintly like mushrooms. That dampness means water is either seeping through the soil or leaking from above, and it has been doing so long enough for the smell to permeate.

Moisture under a house is the precursor to every major foundation problem. It accelerates timber rot in wooden stumps. It creates the conditions for termite (white ant) infestation. It causes clay soils to expand and contract, which moves the stumps, which cracks the walls above 3.

If it smells damp, you need to look harder. If it smells bone dry, you are already in a better position than 40% of the houses I inspect.

Step three: identify the stump material

Shine your torch into the subfloor and look at the stumps—the vertical posts that support the bearers (horizontal beams) which hold up the floor above.

Stumps come in two materials:

Concrete stumps: grey, cylindrical or square, typically 200mm-300mm wide. These are the gold standard. Concrete does not rot. Termites cannot eat concrete. A properly installed concrete stump will last the life of the building 4.

Timber stumps: usually red gum or hardwood, sometimes painted, often visibly weathered. Timber stumps were standard in houses built before the 1970s. They work fine—as long as the subfloor is dry.

Here is the critical decision tree:

• Concrete stumps + dry subfloor = buy with confidence
• Concrete stumps + damp subfloor = investigate the moisture source (fixable, but factor in $5,000-$15,000 for drainage remediation)
• Timber stumps + dry subfloor = acceptable, but budget for restumping within 10-15 years
• Timber stumps + damp subfloor = walk away

That last combination is the one that destroys budgets. Timber plus moisture means the stumps are actively rotting. The rate of deterioration accelerates exponentially once moisture is present. Within five to ten years, individual stumps begin to sink at different rates, causing differential settlement. The floor tilts. Doors stick. Cracks appear in the walls—not hairline cracks, but the zig-zag cracks that follow mortar joints and signal structural movement 5.

Restumping an entire house—ripping out 30-50 timber stumps and replacing them with concrete—costs $30,000-$50,000 minimum. If the bearers and joists above have also rotted, you are looking at $60,000-$100,000 or more. I have a client who was quoted $120,000 for a complete subfloor rebuild on a property they bought without inspecting underneath.

"I tell every buyer the same thing: the one part of a house that cannot be fixed cheaply is the foundation," says Joey Don, Co-Founder of PremiumRea. "Everything else—leaking roof, cracked pipes, outdated kitchen—those are five to ten thousand dollar problems. Foundations are six-figure problems."

Step four: check for ant caps and termite signs

While you are looking at the stumps, check the top of each one. You should see a metal disc or flange sitting between the top of the stump and the bearer above. This is an ant cap 6.

Ant caps do not stop termites. They force termites to build their mud tubes around the cap, making the tubes visible to the naked eye during inspections. Without ant caps, termites can travel from the soil up through the stump and into the bearer without any visible sign until the damage is catastrophic.

If the stumps have ant caps: good. Check whether the caps are intact and whether there are any mud tubes climbing around them.

If the stumps are timber and have no ant caps: this is a red flag. It means there is no early warning system for termite activity. You are relying entirely on periodic pest inspections to catch an infestation before it causes structural damage.

Melbourne's southeast is not the worst area for termites in Victoria—that distinction belongs to the northeast—but the City of Casey, Knox, and Cardinia all have active termite populations. A professional pest inspection costs $300-$500 and should be mandatory for any property with timber stumps 7.

Step five: look for moisture and plumbing signs

While your torch is illuminating the subfloor, scan the soil surface. Healthy soil is uniform in colour—grey or brown, dry to the touch. If you see patches of yellow or green fungal growth on the soil surface, you are looking at sustained moisture. That fungus does not grow overnight. It grows over months or years of consistent dampness.

Also look upward at the underside of the floor and the water pipes running through the subfloor. Are there any drip stains? Water marks? Active leaks? A slow leak from a bathroom drain or laundry pipe can saturate the soil below for years without anyone noticing.

For the property I was inspecting with a client last month in Hampton Park—which we ended up purchasing—the subfloor was damp in one section but bone dry elsewhere. The stumps were concrete. We traced the moisture to a dripping pipe fitting, which was a $400 repair. Because the stumps were concrete, the moisture had not caused any structural damage. If those stumps had been timber, we would have walked.

That is the margin. A $400 pipe repair on concrete stumps versus a $50,000 restumping nightmare on timber stumps. Same moisture. Completely different outcomes. The stump material is the variable that determines whether a damp subfloor is a minor repair or a financial catastrophe 8.

"You are spending $600,000 or more. Get your head under the house. Sniff the air. Look at the stumps. It takes two minutes and it could save you $100,000," says Joey Don.

When to call in the professionals

Everything I have described above is a preliminary assessment. It tells you whether to proceed with confidence, proceed with caution, or walk away immediately.

But it does not replace a professional building and pest inspection. For any property you are serious about purchasing, spend the $500-$600 on a qualified building inspector. They will use moisture meters, check roof cavities, assess the electrical switchboard, and produce a formal report that categorises defects as minor, significant, or major structural 9.

If the report comes back with "Major Structural Defect" in relation to the foundation or subfloor, do not negotiate. Walk away. The cost of remediation is almost always higher than the discount the vendor is willing to offer, and you will carry the disclosure obligation when you eventually sell.

If the report identifies minor issues—surface cracks, a couple of stumps needing adjustment, minor moisture—that is negotiating leverage. We routinely use building reports to negotiate $5,000-$15,000 off the purchase price, which more than covers the inspection cost.

The building inspection is not an expense. It is the cheapest insurance you will ever buy on a six-figure asset.

I know I keep repeating this, but I will say it one more time: the foundation is the one thing you cannot cheaply fix. Check it. Always.