Foundation Inspection Checklist: What to Check Before Buying an Older Home

Buying an older house is exciting until you discover the foundations need $30,000 worth of work six months after settlement. Foundation problems are expensive, disruptive, and almost always present some warning signs before you buy - if you know what to look for.

Here's what you can check yourself at an open inspection, what a building inspector should check for you, and the red flag phrases in inspection reports that sellers hope you'll gloss over.

What you can check yourself at the open inspection

You don't need to be a builder to spot the early signs of foundation trouble. These checks take five minutes and tell you a lot about what's happening underneath.

The door test

Open and close every internal door in the house. Every single one. A door that sticks at the top, drags on the floor, or won't latch properly is one of the earliest signs of foundation movement.

Look at the gap between the door and the frame. It should be roughly even on all four sides. If the gap is 2mm at the top-left and 10mm at the bottom-right, the frame has racked. That means the wall has tilted, and the wall tilted because something underneath moved.

The marble test

Bring a marble or a small ball to the open inspection. Place it on the floor in the middle of each room and let go. On a level floor, it should sit still or roll very slowly. If it takes off toward one wall like it's been kicked, the floor is sloping.

Some slope is normal in older houses. A marble that drifts gently over a few seconds isn't a crisis. A marble that rolls fast enough to hit the skirting board with a click means the floor has dropped significantly on one side.

Do this test in multiple rooms. If every room slopes in the same direction, the whole house has tilted. If different rooms slope different ways, you've got differential settlement, which is harder and more expensive to fix.

Visible cracks

Walk around the outside of the house and look at the brickwork. Stair-step cracks following the mortar joints are a sign of settlement. Horizontal cracks near ground level suggest lateral pressure on the walls.

Inside, check above doorframes and windows. Diagonal cracks running up from the corners of openings indicate the structure is flexing. Check where walls meet ceilings - a gap or a crack running along the join suggests the walls and ceiling are moving independently.

Subfloor access

If the house has a subfloor (crawl space underneath), ask the agent if you can look through the access hatch. You don't need to crawl under - just shine your phone torch in and look at what you can see.

You're looking for stumps that are visibly leaning, timber stumps with splits or rot at the base, packing (bits of wood or metal shims) wedged between the stump top and the bearer, and any standing water or signs of recent flooding.

If the access hatch has been sealed, screwed shut, or "lost", that's worth noting. Not always sinister, but sometimes deliberate.

Drainage around the house

Walk the perimeter. Is the ground sloping toward the house or away from it? Water should always flow away from your foundations. If the garden beds have been built up against the walls, if downpipes discharge directly at the base of the house, or if there's visible pooling near the walls, the drainage is working against the foundations.

Check for large trees within 10 metres of the house. Mature eucalyptus, elms, and liquid ambers draw huge amounts of moisture from the soil and accelerate clay shrinkage around foundations.

Stump condition (if visible)

Some older houses have exposed stumps in carports, under verandahs, or in basements. If you can see any stumps, look at them closely. Timber stumps should be solid with no visible rot, cracks, or lean. Tap them with your knuckle - a solid stump sounds firm, a rotten one sounds hollow.

Concrete stumps should be upright, uncracked, and sitting squarely on their pad. A concrete stump that has tilted, cracked horizontally, or separated from the bearer above it needs replacing.

What a building inspector checks

A standard pre-purchase building inspection covers foundations, but the depth varies enormously between inspectors. Here's what a thorough inspection includes.

Stump condition report

A good inspector will crawl under the house (if accessible) and assess every visible stump. They'll note the type (timber, concrete, steel), condition (good, fair, poor, failed), and whether any have been packed, replaced, or are showing signs of movement.

The report should tell you approximately how many stumps need replacing and a rough timeframe - "within 12 months" versus "within 5 years" is a significant difference in negotiation terms.

Moisture levels

Inspectors use moisture meters to check the subfloor environment. High moisture under the house accelerates timber stump decay and indicates poor ventilation or drainage problems.

They'll also check for rising damp in walls - moisture wicking up from the ground through the brickwork. This doesn't always mean foundation failure, but it does indicate the damp course (the waterproof layer near ground level) has failed or been bridged.

Soil type assessment

Experienced inspectors will note the soil type and its reactivity classification. This matters because it predicts future movement. A house on highly reactive clay in Melbourne's west will behave differently over the next decade than one on sandy loam in the eastern suburbs.

The soil classification also affects how any future restumping work should be designed. Deeper stumps are needed on reactive clay compared to stable soil.

Crack mapping

A thorough inspector doesn't just note "cracks present." They measure them, photograph them, and map where they appear. The pattern of cracking tells you what kind of movement is happening and where it's coming from.

Cracks concentrated on one side of the house suggest localised settlement. Cracks everywhere suggest the whole foundation is moving. Cracks that are wider at the top than the bottom suggest the wall is tilting outward at the top.

Red flags in the vendor's inspection report

If the vendor provides a building inspection report (common at auctions), read it carefully. Some phrases sound reassuring but actually flag problems the inspector didn't want to spell out too bluntly.

If the vendor's report recommends "further investigation," treat that as a warning, not a formality. The inspector saw enough to be concerned but not enough to make a definitive call. That's what structural engineers are for.

Questions to ask the building inspector

Most buyers get a building inspection report, read the summary page, and stop. Ask the inspector directly. A five-minute phone call after the inspection is worth more than re-reading the report three times.

• "If this were your money, would you be concerned about the foundations?" - This cuts through the formal language. Most inspectors will give you a straight answer when asked directly.
• "How many stumps need replacing, and when?" - Pin down the numbers. "Some" is not useful. "Eight out of thirty, within two years" is something you can negotiate on.
• "Is this house on reactive clay?" - If yes, ask what that means for the next 10 years of ownership.
• "Did you find anything that would make you recommend a structural engineer's report?" - If the answer is yes, get one before you commit.
• "What would restumping this house cost, roughly?" - Inspectors aren't quoters, but experienced ones can give you a ballpark.

When to get a structural engineer's report

A building inspector gives you a general assessment. A structural engineer gives you a definitive diagnosis. They're different qualifications, different insurance, different liability.

Get a structural engineer if:

• The building inspector recommends one (always follow this advice)
• You've found cracks wider than 5mm anywhere in the house
• Multiple doors and windows are sticking or out of square
• The floors slope noticeably in more than one room
• The house is pre-1950 and has never been restumped
• There are large trees within 10 metres on reactive clay soil

The engineer's report gives you a document you can take to restumping companies for accurate quotes. It also gives you negotiating power with the vendor - "your house needs $25,000 in foundation work according to a structural engineer" is a strong position at the negotiation table.

Putting it all together

Foundation problems don't have to be deal-breakers. Reblocking is a well-understood process with predictable costs. The problem is buying a house without knowing about it and getting surprised later.

Do your own checks at the open inspection. Get a thorough building inspection from someone who actually crawls under the house. Read the report properly, especially the recommendations section. And if anything flags concern, spend the $500 to $1,200 on a structural engineer before you spend $800,000 on a house with a failing foundation.

Want a quick risk assessment based on the property's age, type, and location? Try the free reblocking assessment tool before your next open inspection.