Some concerned Sydneysiders have noticed cracks emerge in their homes as the drought continues to bite in the city, with one firm reporting inquiries into the issue doubled over summer.

Australia’s unusually long and severe drought in the past few years has meant the Sydney Basin has dried up again. Large areas of Sydney homes are built on clay, which shrinks when it dries up, causing many homes to crack.

Mainmark Ground Engineering business development manager Laurie Andrews said the dry weather had affected homes across NSW.

“After months of little to no rainfall, Sydney has experienced drier than average ground conditions, which can impact the ground under a home’s foundations,” he said. “Houses built on loosely packed soils, sand, and reactive clays can all be particularly affected by extreme weather.

“The recent unprecedented dry conditions in Sydney, combined with periods of occasional heavy rainfall, can cause soil subsidence and building movement.”

Mr Andrews said inquiries from concerned home owners increased during drought and extended wet weather.

“In NSW, the past couple of weeks have been particularly busy with Mainmark receiving double the number of inquiries.”

However, one expert reassured residents, with managing director of ARINA and University of NSW architectural construction adjunct lecturer Geoff Hanmer saying the drought has had a major impact on the ground but should not be a cause for concern in most cases.

“Most of these cracks have no structural significance,” he said. “They might be unsightly but nothing they should be immediately concerned about.”

He said hairline cracks were more a cosmetic concern rather than a structural one.

“The easiest way to monitor this is to put tape over the crack and measure over two points. If they get significantly wider over time it might be wise to call a structural engineer,” Mr Hanmer said.

“If we go back to a more normal weather condition, a lot of these things will effectively close up.”

He said some parts of Sydney and specific building types were more vulnerable to this type of cracking than others.

“Most modern buildings, we’re talking houses, built on strip footings are [more] prone to cracking than homes built on slabs and most double-brick houses are [more] prone to cracking than brick veneer,” he said.

“If you’re on or near the Parramatta River, upstream, west of Gladesville or around any of the other rivers that have flooded historically there’s more likelihood that there is expansive clay.”

He said if home owners had large cracks or cracks that were moving away then that was “a different kettle of fish”.

On their own, the cracks do not necessarily mean that a building is unsafe, according to civil engineer and senior lecturer at the University of Sydney Petr Matous, unless the shifts lead to deformation of structural elements, such as bending or tilting of load-bearing walls.

“When the cause of cracking is drought, filling or covering the cracks does not address the cause but remedial works on foundations can help and decrease further deterioration,” Mr Matous said. “If home owners are worried, they should seek inspections from accredited structural engineers or geotechnical engineers specialised in ‘reactive soils’.

“It is recommended to take photos and record the width of the cracks if they change over time. Such information will help the experts to decide which course of action to take.”