If you live in Washington, D.C., chances are good that you’ve seen metal stars on the facades of buildings while wandering through endless blocks of rowhomes. These stars can add a certain aesthetic to a home, but they are not just for decoration.
Star bolts can be essential in tying your home together. A star bolt is an anchor plate, and they do just that, anchor the non-structural walls to the ones doing all the work. Anchor plates come in many shapes and sizes, but we count ourselves lucky to be in a city where stars are the most prevalent, as we are enamored with their charm.
The construction of most row homes in the District of Columbia are brick and mortar. Mortar used prior to the 1920’s was a lime mortar, which, for many reasons, was replaced by Portland cement upon its arrival on the scene. Now we’re not going to say it’s an inferior product, it certainly has its advantages, however, some of the traits that make it well suited for row-home construction, can also be its downfall.
Lime mortar is softer, it has a lower adhesion rate to masonry materials, and it is more susceptible to deterioration. These things help in seismic events or the settling of the foundation. Where Portland cement would crack, lime mortar is better able to absorb the shock and preserve the brick. Prolonged deterioration could cause your wall to fail.
With all of this being said, when the mortar fails, the entire wall will start to fail and can cause “bellying”, where the walls start to bulge outward. Typical row home construction consists of structural masonry party walls (the walls shared with your neighbor) and the front and back facades. The floor joists and roof rafters are “pocketed” into the party walls and hold everything together. When you have a whole street of connected row homes, it becomes a very solid structure.
The front of a rowhouse however, is seldom tied into the structure of the rest of the home in any significant way. If the wall comes under stress or its mortar starts to crumble, this wall buckles under the pressure and bulges out.
Picture yourself standing in front of a rowhouse. If you were to divide it into floors, you would see floor joists running horizontally from party wall to party wall. It is most likely at this place where you will find star bolts, and that’s because the bolts are connected to a long threaded rod that is connected to the joists. By connecting the star bolts to the structure of the house, you are tying it all together, supporting the facade, and distributing the load.
So there you have it. The stars that are characteristic of DC’s architecture serve a purpose. But it’s not to say they can’t be used decoratively. We’re all for it.