How far should the ends of cotton wicks extend up into the masonry cavity?
The length of the cotton wick inside the cavity depends on the height of mortar droppings in the cavity. If no mortar droppings are present, the end of the wick need only be 1 inch or so. That, however, is not realistic. I recommend about 8 inches of cotton sash cord within the cavity. The end of the cord should extend at least 4 inches above the base of the flashing. The remainder should sit directly on the flashing. Cotton wicks can be tied off to the bottom of wall ties or by some other method to hold them in place before the masonry is installed. In general, I recommend using other methods of weeping walls that allow faster drainage than wicks. Leaving open head joints, using weep hole ventilators, or pulling wicks after a section has been completed are three common methods of accomplishing this.