The Mundic Test and Type Classification
The Mundic Problem: A Guidance Note, published by the Royal Institution of Chartered Surveyors (RICS) in collaboration with specialist engineers, provides the framework for assessing and classifying mundic block properties. Under this guidance, a petrographic analysis — a microscopic examination of core samples taken from the concrete — is carried out by a RICS-approved laboratory. The results determine whether mundic-susceptible aggregate is present and, if so, in what concentration and condition.
Properties are classified as Type A, Type B, or Type C based on the test results. Type A properties show no significant mundic aggregate or very low levels that are not causing active deterioration — these are the most mortgageable, and some mainstream lenders may consider them alongside specialist lenders. Type B properties show moderate levels of mundic aggregate with some signs of deterioration — these are uncertain cases, and lender options are limited. Type C properties show significant mundic aggregate with active or advanced deterioration — these are very difficult or impossible to mortgage, and the structural future of the building is in question.
Without a Mundic test result, virtually no lender will accept a property in a mundic-affected area as mortgage security. The test typically costs £300 to £600 and requires core samples to be taken from the external walls. It is a necessary step for any remortgage application on a potential mundic property, and the earlier in the process it is commissioned the better.
Which Properties Are at Risk from Mundic?
Mundic block construction is concentrated in the former tin and copper mining areas of Cornwall — particularly the areas around Redruth, Camborne, St Austell, Penzance, and the Lizard Peninsula — and to a lesser extent in parts of West Devon around Tavistock and the Tamar Valley. Properties built in these areas between approximately 1900 and 1950 using concrete block construction may be at risk.
Not all properties in these areas will contain mundic aggregate, and not all that do will be significantly affected. The prevalence of mundic varies by location depending on proximity to former mine workings and the sources of aggregate used by local builders. Properties built after the early 1950s are less likely to contain mundic aggregate, as awareness of the problem grew and the use of mine waste aggregate declined. However, because the issue is not visible to the naked eye, a test is the only reliable way to determine the presence and severity of mundic.
Properties built with standard imported or quarried aggregate — or using brick rather than concrete block — will not be affected by mundic. If your property in Cornwall or Devon is built with handmade clay brick or modern concrete block, mundic is unlikely to be a concern. Your surveyor will be able to advise on whether a mundic test is appropriate for your specific property.
