Floor level variation and cracking inspection in Marshall

The brief

We were asked to inspect a house in Marshall, a suburb in the City of Greater Geelong, for floor-level variation.

The inspection was to assess the general structural condition of the house, identify visible signs of structural movement or distress, find the likely causes of the defects and recommend repairs.

Why it needed a structural engineer

Uneven floors and cracked plaster can have more than one cause. Clause 3.1 of the Building and Plumbing Commission's Guide to Standards and Tolerances 2026 says footing and slab systems are designed to accommodate an amount of foundation movement, that this movement may cause minor distress such as cracking to ceilings, floors or walls, and that the presence of distress may not mean the work is outside tolerance. It lists contributing factors such as trees, excessive and localised watering, site surface drainage and water leaks.

In this house, some of the cracks had been patched and repainted before, and cracking was showing again through or beside those repairs. The engineering question was which defects point to movement of the slab and footings, which come from rigid finishes and ageing seals, and what has to be confirmed before anything is repaired again.

What we checked

The inspection was visual and non-destructive. It covered the readily accessible areas inside and outside the house, which is brick veneer on a concrete slab-on-ground, together with indicative floor-level measurements. It looked at:

• the general structural condition of the house;
• the accessible internal and external walls, for cracking, movement, distortion or other signs of structural distress;
• the floor, for noticeable level variation, settlement or deformation;
• doors, windows and other openings, for movement-related distortion or separation;
• the external brickwork, articulation joints and the junctions between materials;
• accessible footing and slab indicators, for visible signs of differential foundation movement.

The floor-level readings are indicative relative site measurements, not a full precision level survey. The concealed footings and founding soil were not exposed or verified.

What we found

Indicative floor levels varied by about 50 mm overall across the accessible rooms, and the cracking was concentrated inside, around rigid finishes and openings. The brick veneer outside had no significant cracking in the areas inspected.

Area	What was seen
Floor levels	About 50 mm overall relative variation across the accessible internal areas, spread across several rooms
Internal walls	Diagonal cracking at multiple locations, mostly running from the corners of doors and other openings
Cornices	Cracking and separation along wall-to-ceiling and cornice junctions
Earlier repairs	Patching and repainting at some crack locations, with cracking visible again through or next to the repaired finishes
Skirtings	Localised gaps between skirting boards and the floor at several locations
External brick veneer	Generally aligned, with no significant cracking through the bricks or mortar joints in the areas inspected
Articulation joints	Joint width varied along the height at some locations; sealant locally split, recessed, detached or deteriorated
Windows	Localised gaps between some window frames and the brickwork, with deteriorated perimeter sealant
Outside the house	Paved, gravel and landscaped areas next to the house, with vegetation along parts of the side; gutters, downpipes and the roofline showed no obvious gross deformation

What the report put the defects down to

The report considered the overall condition consistent with a combination of slab and foundation movement, the normal response of the building, and deterioration of flexible joints and finishes.

• Differential slab and foundation movement. The roughly 50 mm floor-level variation, together with cracking concentrated around rigid internal finishes and openings, is consistent with differential movement of the slab and foundations over time. Potential contributors include soil movement, long-term settlement and construction tolerances.
• Rigid finishes. Plasterboard, cornices and other rigid finishes have limited ability to accommodate differential movement. Movement of the slab and wall framing can therefore cause diagonal cracks at opening corners, cornice separation and local skirting gaps.
• Earlier repairs. Filled or patched cracks can reappear where the underlying movement has not been confirmed as stable.
• Joints and windows. Ageing, weather exposure and repeated differential movement can make external flexible sealants split, recess or detach while the brickwork next to them stays intact.
• Perimeter moisture. Changing moisture conditions around the house can influence the supporting soils and contribute to differential foundation movement. No geotechnical investigation was part of this inspection.

What we recommended

The report set out an order of work: investigate the foundations first, stabilise only where that investigation shows a need, then repair the internal finishes, and reseal the joints and windows.

1. Footing and foundation investigation. Dig targeted trial pits where the floor-level variation is greater and the internal cracking keeps coming back, to confirm the slab edge and footing configuration, footing dimensions, founding depth and condition. Carry out a geotechnical investigation to establish the soil profile, the founding conditions and the possible influence of seasonal moisture changes. Keep the current floor-level readings as the baseline.
2. Slab or footing stabilisation, if required. Decide after the investigation whether stabilisation is needed. Where inadequate founding, differential settlement or continuing loss of support is confirmed, stabilise the affected areas to an engineer-designed detail. Depending on the footing and soil conditions, the method may be conventional underpinning, engineered resin ground stabilisation or injection, screw or helical piles, or another suitable engineered system. Limit the work to the affected areas unless the investigation finds wider deficiencies, and do any level correction or lifting progressively, under controlled conditions, to limit further cracking or distortion.
3. Internal crack repairs, last. Make permanent repairs only after the investigation and any stabilisation. Remove loose or failed earlier repairs, repair plasterboard cracks and cornice junctions with reinforcing tape and a setting or jointing system, then sand, seal and repaint. Refix any loose cornice or ceiling lining first.
4. Skirtings and doors. Once the structure is confirmed stable, refix separated skirting boards, fill remaining gaps with a compatible flexible sealant where appropriate, and adjust or rehang doors that bind or sit out of line. Don't rigidly fill movement gaps before the structural cause is dealt with.
5. Articulation joints. Remove the failed sealant, clean the joint faces, fit a closed-cell backing rod where needed, and reseal continuously with an exterior-grade elastomeric movement-joint sealant. Keep the joints flexible: never fill them with mortar, grout or other rigid material.
6. Windows. Remove the failed sealant between window frames and brickwork and reseal with a flexible exterior-grade sealant that can take differential movement, keeping cavity drainage and weep holes clear.
7. Drainage. Keep surface falls running away from the house so water doesn't pond along the slab edge. Make sure gutters, outlets and downpipes are clear and discharge to a working stormwater system, avoid concentrated roof or surface water next to the foundations, and keep moisture conditions around the house reasonably even.
8. Checks after the work. Recheck selected floor-level points against the baseline, inspect the earlier crack locations, joints and windows once the structural work has settled, and get a further structural assessment if measurable floor movement, widening or recurring cracks, significant door or window distortion, or cracking in the external brickwork develops.

The result

Based on the visual inspection, the report found no evidence of imminent structural instability in the accessible areas, and the house is considered suitable for continued residential use. It treated the floor-level variation and recurrent internal cracking as serviceability issues that warrant a further footing and foundation investigation, with targeted stabilisation to an engineer-designed detail if that investigation shows it is needed.

The report gives the client a clear order of work, with the floor levels recorded at the inspection kept as the baseline for checking any later change, so the cracks are not patched again before the cause is known.

Uneven floors or recurring cracks in your Geelong home?

Our structural inspections include cracked house inspections for homes across Geelong and the surrounding region. Send us photos of the cracks, gaps or uneven floors, where they are in the house and when you first noticed them, through our contact form, or call 03 4250 8105. We'll get back to you with a quote.

To read more first, our article on foundation investigation and repair explains what an engineer looks at and the usual repair options, and stormwater and drainage issues causing structural damage covers how water around a house can lead to foundation movement.