You've seen the steel or cast iron plates on the faces of brick walls downtown. Sometimes they're stars or diamonds, sometimes plain squares. They are there because they serve an essential purpose. They are an affordable solution to strengthening our brick buildings for another generation.
They are literally anchors. Like a ship's anchor that keeps the boat from floating, these anchors keep the exterior walls of a building from “floating” and eventually falling away from the floors and roof.
When brick buildings were constructed years ago, floor joists were supported at each end by inserting them into pockets in the brick walls. These joist ends were stabilized by friction and mortar acting as glue; no mechanical connections were used. The brick wall thus carries the cumulative weight of all the building's floors and roof. On the other two sides of the building, typically the front and back, the joists run parallel to the walls and are not even in contact with them.
Fast forward 100+ years: the old mortar glue has failed. The walls have started to shift, bow, or lean due to several actions, including temperature differentials, moisture degradation, wind events, and eccentric loading. The hard truth is that our old brick buildings in Memphis are "time bombs" when it comes to the risk of collapse because the bricks and the mortar are slowly breaking down & disintegrating. It typically takes 150 years for the old archaic brick and mortar to turn to clay dust and loose sand. However, this process is greatly accelerated by high moisture at the foundations and tops of walls. Evidence of this is something we commonly see on inspections of old brick buildings.
This is where the anchors come in. The steel plates you see are structural retaining washer plates securing, or anchoring, the ends of rods used to attach floor joists or beams to brick walls. The rods go through the brick wall and secure the joists or beams to the anchor plate on the outside, essentially "tying" the floors to the walls.
This restrains the wall's lateral movement and ensures that the joists and beams remain fully seated in their pockets. This improves load transfer between floors and walls in all three axes. This relieves the aging and compressing brick walls from destabilizing eccentricities. Since wall stability failure is most commonly the cause of collapse for this building type, this repair significantly extends the useful life of the building.
Think of this as the "weakest link" or "low-hanging fruit" approach to structural strengthening. It will give our precious historic urban buildings another generation or two of useful service life. This anchoring should usually be installed on all four sides of a building, on each floor and roof. And yes, it is also a relatively low-cost and effective way to provide seismic stabilization.
This is often the first step of a multi-pronged strategy to preserve a building of this type comprehensively. But used alone, it can, in some cases, be an economical way to keep these buildings safe and serviceable for another generation or two. And this practical method has stood the test of time. With roots from Roman times, tie rods and anchor plates have been trusted to reinforce masonry structures. They have become a standard tool in restoration because they are dependable and practical.
At Ozer Engineering, if you have an aging brick building and would like to preserve it or renovate it, we recommend an assessment to determine if these anchors are a good solution. We can then lay out a placement plan.