Masonry Magazine April 1988 Page. 20
The other piece is installed as the facing wythe is constructed, reducing the risk of damage to exposed ties that might occur when unit ties or standard joint reinforcement are used. 3) Adjustable ties can accommodate construction tolerances common in multi-material construction. 4) Adjustable ties can accommodate larger differential movements than standard unit ties or joint reinforcement.
The advantages offered by adjustable tie systems are not without possible problems: 1) Mislocation of adjustable ties placed prior to construction of facing wythes, if extreme, can render the ties useless. 2) Adjustable ties may encourage less than perfect layout of the wall system since a built-in adjustment allowance is available. 3) Large variations in construction tolerances may not allow full engagement of ties intalled before facing wythes are constructed. 4) Improperly positioned ties may result in large vertical tie eccentricity. 5) The structural performance of some adjustable ties in regard to strength and stiffness is less than that of standard unit ties or joint reinforcement.
Adjustable Unit Ties. Adjustable unit ties produced for use with masonry backup, concrete backup, steel frames and steel studs are shown in Figs. 5 and 6. Slot-type ties (dovetail, channel slot, etc.) have been used for a number of years with concrete, steel frame and steel stud backup systems, and are recognized as tie systems capable of accommodating differential movement, as further discussed in Technical Notes 18 Series (see Fig. 5). Other types of adjustable unit tie systems are available for brick with masonry backup and other backup systems. These ties are typically two-piece systems, consisting of a single or double
Adjustable Unit Ties for Masonry Backup
FIG. 6
eye and pintle arrangement (see Fig. 6). Typical installation details are shown in Fig. 7.
Adjustable Assemblies. Adjustable ladder and truss-type joint reinforcement assemblies are available for use in masonry-backed cavity, veneer and grouted wall construction. This joint reinforcement typically consists of rectangular tab or "Z" type extensions, connected to standard joint reinforcement by means of an eye and pintle arrangement (see Fig. 8). Installation details are shown in Fig. 9.
Masonry Re-anchoring Systems
Masonry re-anchoring systems are the most recent development in masonry tie systems. Three general types of systems are being produced and typically consist of a mechanical expansion system, screw system or an epoxy adhesive system (see Fig. 10). These systems are primar-
Adjustable Unit Ties for Steel,
Concrete and Stud Backup
FIG. 5
Adjustable Unit Tie Details
FIG. 7