Technical Booklet C Site Preparation and Resistance to Contaminants and Moisture·Page 30·6.8
Cavity trays on raft foundations and ground beams
Cavity trays with weep holes must be provided where cavity walls are built directly on raft foundations or ground beams to allow moisture transfer through the external leaf.
Where a cavity wall is constructed directly off a raft foundation, ground beam or similar supporting structure a cavity tray should be provided with weep holes every 900 mm to assist in the transfer of moisture through the external leaf (see Diagram 6.3(b)).
Where a cavity tray does not extend the full length of the exposed wall, i.e. above an opening, stop ends and at least two weep holes should be provided.
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