Q A truck making a delivery to my client's building backed into one of the masonry walls and caused a lot of structural damage. The damage is actually more severe than would have been originally expected because a very large section of wall came down around the truck.
Upon further investigation, we determined that the anchors were only embedded as little as ½ in. into the back of the brick veneer. The wall construction was brick veneer over steel stud. The anchors have a 9-gauge delta wire tie embedded in a mortar joint.
We made openings in several wall locations not damaged by the accident and found that the condition was widespread. In all of these cases, the embedment of the tie was less than the recommended depth of one half the thickness of the masonry.
How little tie embedment is considered acceptable?
What can the contractor do to repair this problem?
A I do not know any published values for estimating the reduction of strength when wire ties are embedded less than the minimum of half the depth of the masonry. The capacity of these anchors is dependent on the type of mortar, and more importantly, the actual area of mortar that engages the tie.
The only way that I know to estimate the installed capacity is to perform load tests of these anchors. This test would likely involve removing several random prisms containing wall ties. The program would need to be developed by an engineering firm or testing agency with experience performing similar work. It is important to make sure that the brick is clamped to replicate some compression within the masonry. Otherwise the test results may be unreasonably low.
After performing several of these tests, the engineering firm or testing agency may be able to develop a correlation between tie strength and depth of embedment of the wire ties. Depending on the quality of the correlation discovered, the engineers may be able to estimate the reliable capacity of the existing anchors.
If the tie wire sizes are consistent throughout the building, the depth of penetration is probably related directly to the width of the air space. By drilling small holes in the mortar joints around the building, it is possible to measure the width of the air space throughout the project using a thin hooked wire. This type of procedure can then be used to identify the problem areas.
Reanchoring the masonry in areas that are identified as having questionable anchorage can be very difficult. The primary problem is locating the studs to install the supplemental anchors.