Concrete @ your Fingertips


Question on Mundic

An estate agent advises me that the cottage in Devon I am thinking of buying should be assessed for ‘mundic’ problems. What does this mean?

Answer

The equity value of many mainly pre 1950 houses in Devon and Cornwall has been adversely effected by uncertainties in the nature of the concrete building material used in their original construction. Mundic is a Cornish word used to describe a mineral of iron containing sulphur, known as pyrite or iron pyrites. This mineral occurs frequently in the lodes or veins of tin and copper mined for centuries throughout Cornwall and Devon. Vast quantities of mine waste were extracted and dumped on the surface. During the early part of the 20th century builders used this cheap and readily available source of aggregate for the production of concrete blocks and concrete for construction.In the presence of moisture, the pyrities chemically alters and expands causing concrete to deteriorate. In the 1950s standards for aggregates used in concrete minimised this contamination. Whilst it is still possible that some properties built after 1950 may be affected the problem is more likely to affect concrete properties built between 1900 and 1950. Mortgage lenders currently insist that all pre-1950 concrete or concrete block properties are screened.

The Royal Institute of Chartered Surveyors, the BRE and the Camborne School of Mines have instigated procedures and tests for the problem. A search of the Internet will provide many Test Houses accredited to carry out a survey; alternatively your mortgage provider should be able to recommend a suitable provider.

 
Acknowledgement: The Concrete Society
 
Other references:Royal Institute of Chartered Surveyors ´The Mundic problem - a guidance note. Recommended sampling, examination and classification procedure for suspect concrete building materials in Cornwall and parts of Devon, London,1997
BRE Report ´Taking care of ´mundic´ concrete houses.´ BRE - Royal Institution of Chartered Surveyors, 1992
BRE Report 325 ´Sulfide-related degradation of concrete in southwest England (the mundic problem), 1997