British Standard 5628: Part 3 code of practice for the use of masonry (materials and components, design and workmanship) offers guidance and recommendations on the damp proofing of structures. It recognises that the penetration of water into the fabric of a building has serious consequences for the health of the occupants and for the long term serviceability of the structure. The numerous bridges of the cavity wall commonly require damp proofing protection in the form of a cavity tray and where a flexible damp proof course material is used; the British Standard recognises that many common details cannot be satisfactorily formed on site and that preformed units should be specified for these complex junctions.