Cities reshape and reinvent themselves regularly and organically. Old buildings become obsolete for a variety of reasons, and new buildings replace them. Many a four- or five-story tenement has been knocked down to make way for a shiny, new glass condo tower - and more often than not, when a building gets razed to build something new in its place, there’s at least one building adjacent to the demolition and new construction site. What if you’re that building? What impact can the demo and subsequent construction have on your property, and what can you do to minimize disruption and possible damage?
Potential Effects of Construction Next Door
Major construction can cause or amplify a variety of potential problems for adjacent properties. The main areas of concern are vibration, cracking, movement, and new or changing load patterns. An adjacent property might experience none of those issues - or one, some, or all of them.
“Damage can come in many forms,” says Giulia Alimonti, senior architect with CTLGroup, an international engineering and architectural firm with offices in New York, “including foundation cracking or settlement, building façade movement and cracking. Interior finishes such as drywall and plaster may crack as well. Common types of damage may include airborne debris or over-pressure waves. Ground vibrations may ‘shake’ adjacent structures and, if sufficiently severe, may cause damage and soil settlement.”
There are some precautionary moves that can be made to keep tabs on these potential problems, and head them off before they become serious. Field monitoring can evaluate ground-borne and structural vibrations, measuring their continuing effects during construction. Pre-construction surveys to catalog any existing cracks, followed up with vigilant dynamic monitoring of those cracks’ response to construction can head off worsening cracking problems. Potential movement, settlement and rotation of super- or sub-structural elements can also be monitored during this period and work altered or halted to correct any concerning developments. Lastly - though certainly no less important - adjacent construction activities can influence the size and distribution of loads on a neighboring structure. If an existing building allows the builders next door to use their roof as a staging area, for example, that roof structure must be carefully evaluated by engineers beforehand to assure that the added weight of supplies, equipment, and so forth does not pose a risk to the building or its occupants.
Getting Ahead of the Problem
“Risk mitigation affects virtually all construction sites in New York City,” says Alimonti. “Any time there is an existing building next to a construction project - they can be older, even landmarks, or new buildings, regardless of the age of existing property - there should be steps taken by both owners to minimize the effects of construction on existing structures.”