Mundic Block


Between 1900 and the early 1950s (mid 1960s in certain areas) many properties in Cornwall and parts of Devon were built with concrete constructed of poor quality aggregate from mining waste.

This aggregate was readily available at a minimal cost from the waste tips of old mines throughout the South West.

Unfortunately it has now been established that the minerals contained in the aggregate material can cause a chemical reaction which results in deterioration of the strength and composition of the concrete.

Not all buildings of that era are suspect. Many of the concrete blocks were made from good quality materials such as the course waste product from china clay workings, but as a result mortgage lenders now insist that properties built of mass concrete or block construction are tested if constructed prior to or around the early/mid 1950’s.

Inspections are carried out in accordance with the Royal Institution of Chartered Surveyors Guidelines (amended 1997) in order to ascertain that the property is not structurally affected by concrete degradation.


Concrete made with mining waste containing minerals such as pyrite or iron sulphide, which can alter and result in reduced structural strength subject to certain conditions.


Whilst it is possible that some properties built after 1950 may be affected, the problem is more likely to affect concrete properties built between 1900 and 1965.

With this in mind, mortgage lenders now insist that properties built of mass concrete or block construction, that were constructed prior to the early 1950’s, are tested to ensure that the structure has not been affected by Mundic contamination.


Under the supervision of a qualified Chartered Surveyor, the procedure involves the extraction of, on average, 8-12 core samples from the property. The cores are extracted using a 50mm ( 2″) diamond tipped core drill.

Sampling locations include all accessible walls and foundations plus internal walls and chimneys.

All core holes are re-filled using sand /cement prior to leaving the property.

The samples are then submitted for petrographic analysis and the findings outlined in a detailed report describing the aggregate and condition of the concrete.

In the majority of cases classification of the concrete can be determined after ‘Stage One’, however a ‘Stage Two’ analysis may be necessary in some circumstances.

‘Stage Two’ analysis involves the core sample being sliced into wafer thin segments for further examination under a high powered microscope together with a highly technical mineralogical examination. A Stage Two analysis will not be included in the initial cost.

Stage Three tests can very occasionally be deemed necessary by the laboratory.

It must be stressed that approximately over 80% of properties tested will pass the ‘Stage One’ analysis receiving a ‘Group A’ Classification.

The Chartered Surveyor supervising the test needs to be compliant with all aspects detailed in the 1994 and 1997 ‘Mundic Problem Guidelines’ set out by the RICS and the BRE.

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