- Question: In embedding triangular wire ties in mortar joints, how far off the recommended amount can a contractor be? We're spacing wire ties 16 inches o.c. vertically and 2 feet o.c. horizontally in a one-story utility brick veneer. We're embedding the ties 1 1/2 to 1 1/4 inches. How do we show that 1/4-inch variation is adequate? What test procedure do we use to determine pullout strength, and what should the minimum pullout strength be?
Answer: In Technical Note 44B, "Wall Ties for Brick Masonry," the Brick Institute of America (BIA) recommends that the outside edge of the tie be no closer than 5/8 inch from the outside face of the brick nor farther than half the brick depth from the outside face. For a typical 3-inch-deep brick, this translates to an embedment of 1 3/4 to 3 5/8 inches.
The outside of the tie should be no closer than 5/8 inch from the outside face of the brick nor farther than half the brick depth from the outside face.
To protect ties from corrosion, it generally is better to keep the outside edge of the ties as far away from the outside face of the wall as possible. If the ties are embedded less than half the brick depth, however, pullout strength may not be adequate. If ties are embedded less than this, they should be tested in accordance with ASTM E 754, Test Method for Pullout Resistance of Ties and Anchors Embedded in Masonry Mortar Joints. The pullout strength of the ties should be at least four times the design load on the ties determined by the structural engineer on the project. In brick veneer over steel studs, the top row of anchors may carry 30% of all the wind load on the wall. For a 12-foot-high wall, with anchors 2 feet o.c. and a 20-pound per-square-foot wind load, the tensile force on the anchor may be 12x2x20x0.3 or 144 pounds. With a factor of safety of 4, the failure load should exceed 576 pounds.