This is a view of the north facade of the Alexander Hamilton U.S. Custom House on Bowling Green, a Cass Gilbert building completed in 1907. I have a fondness for this building, aside from its architecture, due to an early project I worked on involving the Africa statue by Daniel Chester French on the northwest corner. Located near multiple subway lines, the stone units were shifting outward and something needed to be done. The vibration from the subways could not be eliminated, so another type of intervention was needed. The removal of a piece at the top in back of the figure revealed a void space inside between the limestone blocks, large enough for a person to stand in. The solution was to install stainless steel cables with turnbuckles attached to opposing stones across the void, tighten them just to remove slack, and reset the stone piece. The cables would go into tension if stones began shifting outward thereby restraining them.* The anchor embedment was deep enough to engage a large mass of stone in resisting the tension. A low-tech, low-cost, reversible, and invisible solution. The statue still looks like its doing well.
I find myself walking past this building now almost daily during my commute to and from the office and I’ve noticed how clean the facade remains clean despite the number of years since its last major restoration project, and despite all the nooks, crannies and ledges that are so irresistible to pigeons. Netting has been installed in such a way that it is nearly invisible except at certain angles. I imagine it was not easy to get the netting just so, but the end result is relatively noninvasive, effective, and low tech.
* Other work at that time included cleaning, repointing, etc., by the project conservators.