Historic Boston homes at risk of sinking, crumbling

Some of Boston’s most expensive and treasured real estate is at risk of sinking and crumbling.

The hidden problem is tucked beneath centuries-old homes.

An organization founded by the Boston City Council in 1986 is keeping close tabs on the issue that threatens thousands of historic homes.

The properties are at risk of structural failure if underground wooden foundations rot due to declining groundwater levels.

Approximately 8,000 buildings constructed on filled land between the mid-1800s and early 1900s are potentially affected.

The Boston Groundwater Trust monitors groundwater levels across the city’s man-made land areas to ensure wooden pilings remain submerged.

“We work with the entities that own the sewers, the drains, the tunnels, making sure that those are tight, that those don’t leak,” said Christian Simonelli, Executive Director of the Boston Groundwater Trust.

Wood pilings can last for centuries underwater, but exposure to oxygen allows microbes to rot the wood, potentially leading to foundational collapses.

Repairing the damage can cost homeowners upwards of $200,000.

“You see a building, and you say, oh, that building looks OK,” Simonelli said regarding the hidden nature of the foundation issues. “Ultimately, if the building owner ignored it, it would be catastrophic for the building.”

The Boston Groundwater Trust tracks reports of damaged pilings and cases where stabilization repairs have been completed.

Repairing a failing foundation is a labor-intensive process.

“Depending on the size of the building, depending on the number of wood piles underneath the building, it could be anywhere from 12 to 18 months,” Simonelli said.

These expenses are rarely covered by insurance policies.

Real estate professionals emphasize the importance of identifying these defects before a property is sold.

Sellers have a legal obligation to share known issues with potential buyers.

“If they find out about something that’s materially wrong with the home, a defect, it is incumbent upon them to disclose that information if they’re selling their home,” said Colleen Barry, CEO of Gibson Sotheby’s International Realty.

A Massachusetts law that went into effect last year now prohibits home buyers from offering to waive home inspections to gain a competitive advantage.

Barry noted that experienced inspectors can often identify the signs of rotting pilings before they become a “dire issue.”

Many of Boston’s most recognized landmarks have required foundational work over the years due to these risks.

The Boston Public Library, Trinity Church and Old South Church are just some of the properties that have had their wooden pilings repaired or replaced over the last century.

To mitigate future risks, the city now requires builders to install groundwater recharge systems and use porous paving materials to allow rainwater to seep back into the soil.

The Boston Groundwater Trust is preparing to deploy new automatic sensors in the spring to monitor groundwater levels more closely.

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