A Good Summer is Bad for StructuresDavid Cook B.Eng C.Eng FICE MCGI

7 December 2018

Our Principle Engineer, David Cook, has been looking back at 2018 and has written an article on the implications of a long hot summer on the stability of our buildings.

We have all enjoyed the long hot summer with clear blue skies and minimal rain. This however has a downside to the structural integrity of the UK housing stock.

A great proportion of East Anglia is underlain with boulder clay deposited during the last Ice Age. This clay changes in volume with a variation of moisture content. In normal summers of dry spells followed by rain, the fluctuation in moisture content of these soils is generally not significant. This year however, the prolonged dry spell has led to significant changes in moisture content of the soils and subsequent volumetric changes, similar to those experienced after the summer of 1976.

Just like in 1976 we have seen a sudden increase in properties we have found with subsidence issues. Within the practice we are receiving reports of 2-3 new damaged properties per week.

Unfortunately, it’s not as simple as waiting for the winter rains to arrive.

Due to the low permeability of the clays it may take several years for the normal moisture content levels to re-establish.

If the 1976 models are repeated, the number of properties with damage identified will increase over the next two years due to a combination of structures initially bridging voids, before subsequently failing and the issues only being noticed at the time of sale of the property.

Fortunately, the experiences of 1976 laid the foundations to modern practice. Guidelines that were developed at this time are now still in place and insurance companies are better equipped to deal with the issues.

Tell-tale symptoms of subsidence are tapering cracks, cracks that arch over the area of movement and noticeable distortions of the brickwork or structure.

We hope that you do not come across any of these issues, however if you do, please do not hesitate to call and we will be happy to discuss.