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House cracks in Hobart: a crack and foundation report
Cracks in brick walls, doors that jam and floors that slope all have a cause. A licensed structural engineer measures each crack, rates it against the AS 2870 damage categories, finds what is moving the footings and tells you whether the answer is drainage, monitoring or a foundation repair. We design repairs. We never sell them.
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We inspect, diagnose, design and certify. We never sell the repair.
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Get a fixed quote for a crack report
Send photos of the cracks, close up and from further back, with the suburb and when you first noticed them.
From $590 + GST. No obligation. Or call 03 6146 4747
In short
A crack and foundation report is a licensed engineer's on-site assessment of cracks, a sinking corner or a sagging floor. In Hobart it starts from $590 + GST. Each crack is measured and rated against the AS 2870 damage categories, from Category 0 (under 0.1 mm) to Category 5 (over 25 mm), and the report gives the likely cause, severity and what to do next.
- Fee
- From $590 + GST, fixed before we start
- Crack rating
- AS 2870 damage Categories 0–5
- You receive
- Likely cause, severity and repair priority
Severity
Is the crack in my wall serious?
A crack is more likely to be serious when it is 5 mm or wider, still growing, or comes with doors that jam, floors that slope or a wall that leans. AS 2870, the Australian standard for residential slabs and footings, rates wall damage in six categories.
- Cat 0Negligible< 0.1 mm
Hairline cracks.
- Cat 1Very slight< 1 mm
Fine cracks which do not need repair.
- Cat 2Slight< 5 mm
Cracks noticeable but easily filled. Doors and windows stick slightly.
- Cat 3Moderate5–15 mm
Cracks can be repaired; some wall may need replacing. Doors and windows stick, service pipes can fracture, weathertightness often impaired.
- Cat 4Severe15–25 mm
Extensive repair: sections of wall broken out and replaced. Frames distort, walls lean or bulge, some loss of bearing in beams.
- Cat 5Very severe> 25 mm
Major repair, partial or complete rebuilding. Beams lose bearing, walls lean badly and need shoring. Danger of instability.
Cracks in brick walls: what the pattern tells you
Cracks in brick and sandstone walls usually follow the mortar joints, so the shape of the crack shows how the wall has moved. A stepped crack often means one part of the footing has moved relative to another. A tapered crack, wider at one end than the other, shows which way the wall has moved.
Horizontal cracks deserve prompt attention because they can mean sideways pressure, roof thrust or corroded wall ties. In weatherboard homes the same movement shows inside instead, as cracked plaster, cornices pulling away and doors that bind.
These are common readings, not a diagnosis. Our guide to cracks in walls and when to worry covers each pattern in more depth.
Four crack patterns an engineer reads first
- A · Stepped: follows the mortar joints up and across. Often a sign one part of the wall has moved relative to another.
- B · From a window or door corner: openings concentrate stress, so movement tends to show at their corners first.
- C · Vertical: note whether it's wider at the top or the bottom. The taper shows which way the wall has moved.
- D · Horizontal: can point to sideways pressure, roof thrust or corroding wall ties. Worth an engineer's look.
Causes
Why do Hobart houses crack and move?
House cracks in Hobart usually trace back to a change in the ground under the footings. The report names which of these is at work, because each one has a different fix.
- Reactive clay. Clays weathered from dolerite are documented as expansive in Hobart. Mineral Resources Tasmania reports link them to cracked houses in Lindisfarne and Taroona, and describe expansive clays in Lenah Valley.
- Water. A leaking pipe, a downpipe emptying beside a footing or poor site drainage soaks and softens the clay under one part of the house.
- Trees. Roots draw moisture from the soil near a footing, so that side shrinks in dry spells.
- Fill and old footings. Poorly compacted fill keeps settling, and shallow footings under older homes follow the ground.
- Slopes. On steep blocks the engineer checks the Landslip Hazard Code bands. Rosetta and Taroona are documented landslide areas, and a slope problem needs a landslip report rather than a crack repair.
More on local ground in Hobart soils, site classes and why houses crack.
What moves a house? Four common causes
- Trees and roots draw moisture from the soil near a footing, so clay under that side shrinks.
- Reactive clay swells when wet and shrinks when dry, moving footings with the seasons.
- Leaking pipes or poor drainage soak and soften the ground under part of the house.
- Poorly compacted fill keeps settling under a footing long after the house is built.
Plain terms
Sinking house, subsidence or a sagging floor: what's the difference?
These words describe different kinds of movement, and the engineer's first job is to work out which one you have.
- Subsidence
- The ground under a footing drops, often after it dries out, washes out or softens. Part of the house goes down with it.
- Settlement
- Soil or fill compresses under the weight of the house. Usually early in a building's life, or after a leak.
- Heave
- Reactive clay swells when it gets wetter and lifts a footing or slab, often near a leak.
- Seasonal movement
- Cracks that open in dry periods and close in wet ones. Often managed, not repaired.
- Sagging floor
- A raised timber floor that dips between walls, usually from failed stumps, decayed bearers or undersized framing.
Monitoring
How does crack monitoring work?
Crack monitoring means measuring the same cracks at set intervals, using tell-tale gauges or fixed measuring points, and comparing each reading with the first. It answers the question a single visit can't: is the crack stable, opening and closing with the seasons, or still growing?
A seasonal crack in reactive clay is often managed with drainage and maintenance. A crack that grows through both wet and dry periods points to ongoing movement that may need a repair. If your report recommends monitoring, it sets the reading interval and the change that would need action, and we can quote the follow-up readings.
Crack width readings over a year
- Seasonal movement
- Progressive movement
View the data
| Months since first reading | Seasonal movement | Progressive movement |
|---|---|---|
| 0 | 1.2 | 1.2 |
| 2 | 1.6 | 1.6 |
| 4 | 1.9 | 2.1 |
| 6 | 1.5 | 2.3 |
| 8 | 1.1 | 2.7 |
| 10 | 1.4 | 3.1 |
| 12 | 1.3 | 3.4 |
Foundation repair
What does the report recommend for foundation repair?
The report recommends the smallest fix that deals with the cause, and many cracks need no foundation repair at all. Typical outcomes:
| What the engineer finds | Usual recommendation | Next step |
|---|---|---|
| Fine cracks (Category 0–1), no ongoing movement | Patch and repaint at the next repaint | No engineering needed |
| Seasonal movement made worse by a leak, a downpipe or a tree | Fix the water source or manage the tree, monitor, then repair the cracks | Plumber or arborist, then monitoring |
| A footing that has lost support and is still moving | Underpinning, designed to suit the soil and the cause | Underpinning design and certification |
| Rotten, sunken or leaning stumps under a raised floor | Restumping or relevelling | Restumping engineering |
| Movement of the slope itself | Landslip assessment before any repair | Landslip report |
| Cause not clear from the visit | Soil investigation or a period of monitoring | Site classification or monitoring |
General outcomes only. Your report's recommendation depends on what the engineer finds on site.
Already have a repair quote?
Don't sign until the cause is known. If a contractor has quoted underpinning, our underpinning second opinion from $390 + GST checks whether the evidence supports it. Want the whole house checked instead? See the structural inspection.
Related services
If the report finds a repair is needed
Underpinning advice, design & certification
An independent second opinion on an underpinning quote, then design, stage inspections and certification. We never sell or install underpinning.
Learn more
Site classification & footings
Soil tests and AS 2870 site classification, then slab and footing designs that suit the ground, with a Form 35 for your building surveyor.
Learn more
Structural inspection & report
A licensed structural engineer inspects your house and signs a report on what's moving, why, how serious it is and what to do next.
Learn moreFAQ
House cracks and foundation FAQs
Still unsure? Call 03 6146 4747 or send photos for a fixed quote.