Q: How frequently should loop ties be placed in the wall system when they are connecting brick masonry to concrete masonry backup?
A: The requirement and the frequency of ties used to connect brick masonry walls to concrete masonry backup walls are based on the diameter of the wire and the configuration of the tie. This requirement is included in "
The Building Code Requirements for Masonry Structures ACI 530-99/ASCE 5-99/TMS 402-99," Reported by The Masonry Standards Joint Committee (MSJC) 1999, document and is based on the buckling strength of the ties for inward loads.
Provided that the distance between the wythes does not exceed a width of 4 1/2 inches, W1.7 (No. 9 wire) ties are used for each 2-2/3 square feet of wall area. W2.8 (3/16 inch diameter wire) can support 4 1/2 square feet of wall area. Ties that contain cavity drips require twice the frequency: 1-1/3 square feet for W1.7 and 2-1/4 square feet for W2.8 ties.
Larger spaces can be used if a detailed wall tie analysis or testing is performed.
The recently released 2002 MSJC document now states in Paragraph 126.96.36.199.2 that "Wall ties shall be without cavity drips."