An EWS1 assessment is required every 5 years for each building or block. This means multiple sellers located in one block can use the same assessment to assist with the sale of their property.
Five years is intended to capture any renovation or adaptation work done to the building, as well as maintenance over that period.
However, a new EWS1 may be required within the 5-year period if substantial works have been completed to a property, affecting the original conclusions.