What does unlevel buildings mean?

Unlevel buildings are the result of weak ground and/or subsidence.

The appearance of internal or external wall cracks, inability to open and close windows and doors, cracked floors and more can all signal an unlevel building. Once a building becomes unlevel, it is important to fix it right away, or risk further damage and potential hazards. This requires foundation repair, footing repairs, and house re-levelling.

Unlevel heritage buildings

Many heritage buildings are unlevel simply because they are old, and have been exposed to conditions like subsidence for so many years. Mainmark can re-level the building, resolving structural damage and often closing up internal and external wall cracks.

Mainmark has successfully given hundreds of heritage buildings a new lease of life, strengthening them to stand well into the future. Our re-levelling methods which include foundation levelling work because they stabilise the ground underneath the heritage building, raise and re-level the building, then support it.

What causes unlevel buildings?

A loss of ground moisture, such as in drought conditions, can cause buildings to subside and become unlevel. The weight of the building causes it to sink, but the nature of soil and clay shrinkage is that the foundation subsidence is never usually uniform. Loss of support varies across the structure, often causing cracks to form. Often, as the soil or clay becomes moist again and expands, some of the damage may be reversed. However, without ground compaction, all wall cracks are prone to reopen with the next extended dry period.

Earthquakes can cause unlevel buildings and soil liquefaction, which makes previously-stable soil behave like a liquid, causing buildings to become extremely unstable. In many cases the damage that caused the building to become unlevel happens over very long periods of time, making it difficult to pinpoint the exact cause. Regardless of the cause, subsidence repair is possible, and unlevel buildings can be re-levelled and re-supported.

Likely causes:

Water flooding the ground

Drought drying out soil

Washaways from broken pipes (such as water, sewer, stormwater drainage)

Poorly compacted fill

Liquid, gas or mineral resources being removed from the ground


Earthquake and seismic activity, often resulting in liquefaction

Tree roots can suck moisture from the ground

Vibrations caused by heavy road traffic or by machinery

Absence of an organised footing system – in very old buildings or in buildings with additions or alterations

Nearby excavation

Heavy loading

Deterioration of retaining walls

How to fix unlevel buildings?

Mainmark specialises in raising, re-levelling, and re-supporting unlevel buildings by treating the foundation subsidence beneath them which, in turn, allows for the foundation slab to return to level. For example, we can inject structural resins into the foundation ground under the building’s footings for foundation repair and footing repairs. The resins expand together chemically, creating pressure. That pressure lifts the building back to its correct level. Then, if there are weak layers in the ground, continuing injection at deeper levels can resolve this by compacting the ground, densifying and strengthening it to increase its bearing capacity for the future.

Alternatively, we can undertake JOG Computer-Controlled Grouting for re-levelling. Extremely successful in subsidence repair, this award winning method was used to re-level the Christchurch Art Gallery after it suffered building subsidence following an earthquake. JOG is a computerised level correction system that involves, in sequence and rapid succession, grout injection via multiple injection ports. This creates multiple localised hydraulic forces, strategically-arranged over large areas, to effectively float a structure back to level. In some soil conditions, Mainmark can increase the bearing capacity of weak strata by as much as 500 per cent.

Mainmark’s concrete slab levelling methods are fast, efficient, and cost effective; they don’t require you to vacate the building while work is being done.

Various product warranties and Building Code requirements apply (please contact us to see which apply in your region or country).

Key benefits of Mainmark’s building levelling methods include:

Floors and buildings are brought back to level

Non-invasive techniques keep further damage to the building, and the landscaping around it, to an absolute minimum

We don’t tear up floors and excavate ground, so historical integrity remains unaffected

Internal and external wall cracks generally close up, leaving only cosmetic treatment (plastering, painting, and re-pointing brickwork)

Jammed doors and windows can usually operate properly again

Methods are effective on various foundations, such as, bluestone, brick and sandstone.

Mainmark building levelling methods used for heritage buildings: