Our firm used ties with cavity drips to prevent water from migrating across the wire and reaching the backup wythe. In the 2002 version of ACI 530/ASCE 5/TMS402, the end of paragraph 126.96.36.199.2 states “wall ties shall be without cavity drips.”
In the following paragraph, however, allowances are included for adjustable ties. The commentary states that the use of cavity wall ties with drips (bends in the ties to prevent moisture migration) has been eliminated because of the reduced load capacity.
How can drips be more flexible than the offset permitted in adjustable ties? If drips are not used, how can water be prevented from moving from the back of the veneer to the face of the backup during wind-driven rains and associated water penetration?
Wall ties without cavity drips, as described in paragraph 188.8.131.52.2, are those types that meet the spacing requirements listed in Section 184.108.40.206.4. These spacing requirements are 1 tie for every 2 2/3 square feet when the tie diameter is W1.7 and 4 1/2 square feet per tie when the wire size is W2.8.
Adjustable ties, on the other hand, need to be provided at a rate of 1 tie for every 1.77 square feet of wall area. Drips provided in the wall ties increase the flexibility and greatly decrease the strength of the ties. If ties with drips are used, the spacing would likely need to be similar to that required for adjustable ties, provided that the drips do not make the ties weaker or have a higher flexibility than the adjustable ties.
I do not believe that the drips in wall ties serve any significant function and therefore are not needed. It has been my experience that water typically does not travel across a clean wire tire to the backup. Water travels over a tie covered with mortar droppings. Mortar that accumulates on the ties negates the effects of a drip in any case.
Rather than using drips, concentrate on reducing the amount of mortar droppings in the cavity.