Let’s assume you live in or manage a multifamily residential building in one of New York City’s five boroughs, and you find out that the owner of the property adjacent to yours is planning to undergo a construction project. It could be work inside the existing building, say to provide a higher floor-to-ceiling height in the cellar by lowering the cellar floor, or it could be a major construction project involving the demolition of the existing building and construction of a new high-rise office tower or luxury condominium. Regardless of the plan or proposed development, you may start to become concerned about the impact the project will have on your building, and you may wonder what steps you should take in order to protect your building.
A good start would be to reach out to the team of professionals you currently work with—your property management company, attorney, and engineer. These professionals can evaluate the proposed development, and provide guidance regarding protection of your building and property prior to and during demolition and construction on the adjacent site. Once you become aware of a proposed project, it is not too early to begin!
The New York City Building Code dedicates an entire chapter, Chapter 33, to ensure safety during the demolition of existing buildings, and to ensure safety during all construction. The code contains very specific language to protect building and property adjacent to demolition, excavation, or development, and includes provisions for the developer to notify the adjoining property owner, inspect the property, and protect it as required. However, it is in your best interest to be proactive in safeguarding your building, and early involvement usually leads to the best possible outcome. Contact your team as soon as you learn of any planned development on an adjacent property. Your engineer, in conjunction with his expeditor, can obtain any plans filed with the New York City Department of Buildings. This will inform your team as to what to expect, and will allow time to plan accordingly.
As an example, consider the case of a boutique hotel planned for a site adjacent to a 16-story residential building (first floor commercial, remainder residential) located in Midtown Manhattan. The residential building team, which included The Falcon Group, worked with the developer of the hotel to stabilize, protect, and improve the residential building. A top-down stabilization approach was utilized. The initial step was to stabilize the first floor exterior masonry wall, which was exposed once the building on the hotel site was demolished, with structural steel channels secured to the outside face of the wall. The next step was to stabilize the cellar floor rubble foundation wall, as rock removal was required at the lowest level of the hotel site, and vibrations from the rock excavation would jeopardize the stability of the rubble foundation wall. This was accomplished by shoring the building, removing the rubble wall in its entirely, and replacing it with a reinforced concrete foundation wall. Once this was completed, rock excavation could be done safely. The entire process, including rock removal, was carefully monitored. It should be noted that the entire cost of the stabilization project, including engineering and attorney fees, was borne by the developer.
In another case, a 20-story luxury condominium was to be constructed adjacent to a five-story residential building on the Upper West Side. The condominium foundation drawings indicated secant piles to be installed along the property line, but the existing residential building team, which included The Falcon Group, was concerned with potential damage resulting from vibrations associated with the secant pile installation. A vibration monitoring program was implemented, which established threshold limits for vibrations measured at the exterior face of the existing building wall, at grade, adjacent to the construction site. If the threshold limits were approached, the contractor would be required to adjust the pile installation accordingly. The vibration monitors were installed prior to construction. The secant piles were then installed, without incident. As the luxury condominium went up, measures were taken to protect the existing residential building, including protection of windows, the fire escape, and rooftop equipment. Again, the entire cost of protecting the existing building, including engineering and attorney fees, was borne by the developer of the luxury condominium.
These are but two examples of how early involvement and careful planning can be used to protect your building from potential hazards resulting from adjacent lot construction. Typically, a preconstruction survey, which may include crack monitors, is performed prior to excavation and construction in order to provide a baseline with respect to the condition of the existing structure. Monitoring, utilizing both optical monitors and vibration monitors during excavation and construction, provides information with respect to any movement or changes to equilibrium experienced by the building. This information provides the team with the opportunity to act before damage is done to the existing structure, and often takes the form of a revision to the means and methods of construction used by the contractor. Other measures incorporated by the contractor to keep the existing building intact may include protection of the façade, roof, and rooftop equipment. Once the project has been completed, a post-construction survey should be performed and compared to the preconstruction survey as an additional check to ascertain no damage was done during construction.
All costs for these services and provisions are borne by the developer as per an access agreement, which may also include provisions for compensation due to inconvenience experienced by you, the stakeholders of the existing building. Falcon will work closely with your attorney, who may not have expertise in this field. Falcon typically advises regarding technical information to be included in the access agreement, and reviews drafts of the agreement. A well written access agreement is critical to safeguard your interests, avoid potential problems with subsequent litigation, and protect your building!
John McDonald, PE, is a senior engineer at The Falcon Group, New York, N.Y.