Wall weeps should be used wherever water could collect inside a cavity wall, such as over external lintels, or wherever a cavity tray system is installed. To work effectively wall weeps should be placed directly on top of the base of a cavity tray or DPC, or on the front flange of the lintel. Wall weeps should be spaced at 450mm centres to comply with NHBC recommendations.
Care should be taken to ensure the wall weep is kept clear of mortar and does not become blocked. This is particularly important at the back of the weep which could be blocked by mortar droppings from above.