Kim BriscoeInsurers and contractors believe cracks which have appeared in houses in a Norwich street could have been caused by a form of subsidence.Kim Briscoe

Insurers and contractors believe cracks which have appeared in houses in a Norwich street could have been caused by a form of subsidence.

Investigations are still ongoing at the homes in Plumstead Road, some of which have been shored up with scaffolding after large cracks in the walls appeared in just a few days.

Aviva, one of the insurers involved, said consulting engineers involved in the project have told them they believe what has happened in Plumstead Road is technically called 'solution feature' - essentially a hole in or beneath the ground, which can cause subsidence.

So far six homes have been affected to varying degrees, with some having some dangerously large cracks, while others just a few small cracks.

Norwich is renowned for its subsidence problems due to a proliferation of chalk mines and tunnels.

Most memorably an Eastern Counties' red bus fell into chalk workings in Earlham Road in 1988.

Cunningham Lindsey UK are loss adjustors who work for the insurance industry and are involved in working on some of the claims in Plumstead Road.

John Laidler, from Cunningham's, said: 'The ground under Norwich is made up of chalk and this rock can gradually dissolve in water over a period of many years forming fissures or voids in the ground.

'In some cases, these will fill up with surface soil, but in others, the void can migrate up to the surface exposing a hole.

'These features are unpredictable and can affect buildings, roads or pavings. Holes often appear after extended periods of very wet weather.'

Norwich-based Canham Consulting, the engineers looking into the problems at Plumstead Road, will use ground probes to establish the extent of the problem. Depending on the findings it may be possible to the fill the voids or support the affected parts of buildings on new, deeper foundations.

Part of a driveway at a home on the opposite side of the road has also sunk slightly, but Norwich City Council has previously said it does not believe there are any issues with the road itself.

Do you have a story for the Evening News? Contact reporter Kim Briscoe on 01603 772419 or email kim.briscoe@archant.co.uk.