Whole Lotta Shakin’ Goin’ On Next Door? How To Protect Your Building
It has been said that good fences make good neighbors, but there is something to be said for vibration monitors, too.
Vibration data and other tools can be an important part of a pre-construction monitoring program that protects an existing building from inadvertent damage caused by adjacent construction work or demolition.
“It is critical that a pre-construction survey takes place prior to the start of any demolition or construction activity,” said Kathleen Strnad, a senior associate with structural engineers Klein & Hoffman. “This will document your building and its condition before any work next door happens so that you have a benchmark or a snapshot of its condition.”
Should damage occur, she said, the building owner can reference the survey and bring the incident to their neighbor’s attention.
Any building is vulnerable to the risks of nearby excavation or earth retention work, whether or not it shares a party wall with its neighbor. However, older buildings are particularly at risk.
Strnad noted that a load-bearing masonry structure built on a rubble foundation in sandy soil is more likely to be impacted by the vibrations from sheet pile installation than a much-taller modern concrete frame structure with deep foundations. But with the right construction monitoring process, even a very old building stands a chance next to a major construction project.
One of Klein & Hoffman’s clients is a 140-year-old church in Chicago whose neighbors include a 25-story residential high-rise completed four years ago. Klein & Hoffman performed a pre-construction study for the church, implemented a vibration monitoring program and continued to watch for impacts on the historic structure during the entire length of the construction project.
“Deep pile foundations were dug only a few feet from our church's very old foundations, with virtually no negative effect on the church building,” said Father Joseph Chamblain, pastor at Assumption Catholic Church.
Strnad said a monitoring program typically starts with a pre-construction survey to document a building’s condition. This can be as simple as engineers examining the building for cracks, deterioration of building materials, structure settlement or other pre-existing issues and sharing their report with the client. To get a better understanding of the building's structural history, a review of available documents and reports is performed.
“Documenting the condition of their building prior to adjacent construction occurring gives a property owner a direct comparison if damage did occur during the construction processes,” said Terrence McDonnell, a Klein & Hoffman associate principal.
The monitoring team should strive to collect and examine soil studies, blueprints, construction schedules and other documents created by the builders of the new building next door. McDonnell noted that some states, such as Illinois, hold property owners performing construction responsible for legitimate damage caused to an adjacent property by construction activity.
By examining construction documents ahead of time, monitoring teams can educate property owners on possible risks and sometimes provide suggestions that will reduce the risk of damage. Avoiding even incidental damage can save property owners from many hours of explanations and rebuilding trust with their neighbors in the future, he said.
Once work is underway, vibration monitoring can alert stakeholders on both sides of the property line if ground movements or vibrations from pile driving or other heavy equipment activities exceed threshold levels. Problems may then be evaluated and corrected using a pre-established procedure that avoids unnecessary finger-pointing or conflict.
Other studies include settlement monitoring and periodic surveys of existing building facades.
“A land surveyor will tag the facade of the existing building,” Strnad said. “Then, after demolition or excavation activity, the surveyor will perform another reading in the same spot to see if there's any vertical or horizontal movement of that wall.”
An additional benefit of performing the pre-construction analysis, she said, is that the exercise gets people thinking about long-term impacts to their building. Exterior wall maintenance work that may have been delayed might become a higher priority if there is to be only a 6-inch space between buildings, as is common in urban areas.
“If you need to perform tuckpointing on an exposed masonry wall, you might not be able to access that facade anymore once the new building goes up next door,” she said.
In addition to blocking sightlines and accessibility, the presence of the new building next door might also require that facing windows in the older building be fire-rated.
Whether the new neighbor will be a low-rise or a skyscraper, McDonnell said owners of existing buildings should conduct at least some measure of pre-construction monitoring.
“The type or size of the new building is in some ways irrelevant,” he said. “A building is a candidate for monitoring if it is in close proximity or if there's heavy machinery or equipment being used next door.”
This article was produced in collaboration between Studio B and Klein & Hoffman. Bisnow news staff was not involved in the production of this content.
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