Subsidence Survey & Natural Ground Assessment

If you are concerned about subsidence or natural ground movement, this assessment considers the visible condition of the property alongside relevant geological factors.

The service combines a physical inspection of the building with professional analysis of relevant British Geological Survey (BGS) ground information. It can be useful for buyers and owners where there are concerns about subsidence, cracking, previous movement or potentially susceptible ground conditions.

What does a subsidence assessment consider?

Subsidence cannot reliably be diagnosed from a single crack or geological risk rating. The building and the ground beneath it need to be considered together.

The inspection considers visible cracking and distortion, the distribution and apparent significance of movement, the form and age of the building, extensions and alterations, local drainage and other relevant site observations.

This is considered alongside available geological information, including ground conditions associated with shrink-swell clay, compressible ground, soluble rocks, landslide potential, running sand and other natural ground hazards where relevant to the property.

How is BGS ground information used?

British Geological Survey datasets provide useful information about geological conditions and susceptibility to particular forms of natural ground movement. Relevant mapping can be used to place observations at the property into their wider geological context.

A mapped susceptibility does not mean that a particular building is subsiding. Equally, a low mapped susceptibility does not replace inspection of visible evidence at the property. Geological information is therefore used as one part of the assessment rather than as a diagnosis on its own.

When can this type of survey be useful?

A natural ground and subsidence assessment may be appropriate where a buyer or owner is concerned about possible movement, where previous subsidence has been reported, where cracking requires consideration alongside ground conditions, or where the property lies in an area with potentially significant geological characteristics.

It can also help when general searches or environmental reports identify ground-movement susceptibility but provide little explanation of what that information means for the individual property.

Cracks do not automatically mean subsidence

Cracking has many possible causes. Material shrinkage, thermal movement, settlement, alterations, differential movement between parts of a building and local defects can sometimes produce symptoms that concern owners or buyers.

The pattern, location, orientation and history of cracking, together with related movement elsewhere in the building, are generally more informative than considering crack width or appearance in isolation.

Natural ground assessment or crack investigation?

If your principal concern is an existing crack or visible movement and you want the building itself investigated, our Crack & Structural Movement Investigation may be the more appropriate starting point.

If the question specifically concerns subsidence risk, geological conditions or how observed movement relates to the ground beneath the property, this Natural Ground Assessment provides the additional geological context.

What happens after the inspection?

The purpose is to provide a proportionate assessment of the evidence available at the time of inspection. Where the findings justify further investigation, this may include recommendations for monitoring, drainage investigation, arboricultural input, structural engineering advice or other specialist investigation depending on the circumstances.

Not every indication of movement requires extensive investigation or structural intervention. The objective is to distinguish between evidence that can reasonably be monitored or managed and circumstances where further investigation is justified.

For further background, see our guide to subsidence, settlement and seasonal movement.