National framework proposed for foundation risk modelling

What causes foundation damage?

Foundation damage often results from several processes acting together. Soil subsidence can cause uneven settlement beneath buildings. Low groundwater levels can expose wooden piles to oxygen, leading to fungal decay. Changes in soil moisture can also cause peat oxidation and the shrinking or swelling of clay. Foundation problems can affect both the structure and use of a building. The process may lead to cracks, tilted floors, sticking doors, moisture problems and, in severe cases, safety concerns.

Climate change can increase some of these risks, especially through more frequent or prolonged drought. The proposed model would therefore use climate scenarios alongside historical and current data. However, the report notes that knowledge remains incomplete. For example, there is still limited information about bacterial decay in wooden piles and about damage functions for several foundation-related hazards.

Why is a common framework needed?

Existing methods use different definitions, data, scales and risk classes. Some focus on neighbourhoods, while others assess individual buildings. They may also treat hazards, vulnerability and damage in different ways. This makes it difficult to compare results or understand why two methods produce different outcomes.

A common framework can bring these elements together in a transparent way. The proposed model separates the physical hazard, the buildings exposed to it, their vulnerability and the resulting damage and consequences. This structure makes it easier to identify data gaps, show uncertainty and update individual modules when new knowledge becomes available. It can also help ensure that similar buildings in similar conditions receive more consistent assessments.

How would the model work?

The framework combines three main elements: the physical hazard, the buildings exposed to it and their vulnerability. Separate modules would use data on soil, groundwater, climate, building characteristics and foundation types. The model could then estimate outcomes such as the probability of damage, expected damage level, remaining service life or repair costs. It could also connect risk levels to possible follow-up actions, ranging from monitoring to inspection or intervention.

The report recommends separate risk scores for different damage mechanisms. Risks from wooden-pile decay, uneven settlement, moisture and damaged utility connections have different causes and time scales. Combining them into one overall score could therefore hide important differences. The model should also show the quality of the underlying data and the uncertainty of its results.

How would the model support decisions?

The model is intended to support screening and prioritisation, not to provide a final diagnosis for an individual building. A high risk score does not mean that damage will certainly occur, while a low score does not rule it out. The report therefore advises users not to take measures based only on model results. An elevated risk should first lead to monitoring, inspection or more detailed investigation.

The proposed outputs are intended for several users, including homeowners, public authorities, banks and insurers. For these organisations, consistent information could support decisions about damage probability, repair costs and changes in property value. Further development is still needed before the framework can become an operational national model, particularly in relation to data quality, model validation and clear thresholds for action.