In the last 25 years, we have seen a considerable increase in the use of new and unconventional methods for the remedial treatment of building defects. Some of the materials and techniques used have been employed long enough for an assessment to be made of their efficacy based on field experience. Some have only been evaluated by accelerated laboratory methods and do not yet have the full support of service records. Other products are declining in importance as a result of a ‘lack of approval’ by the independent bodies that pronounce on these matters.