Rotting wood is threatening expensive homes in Boston: The cost and benefit of personal character

Boston is one of my favorite cities. From its history to its
academic institutions to its culture, it is always a fascinating place to
visit. But if I’m going to revisit some of its most expensive real estate, I’d
better hurry.

It turns out, depleted groundwater levels are causing the rot of wooden piles that support historic buildings across the city. In particular, homes in the Back Bay, the South End, and Beacon Hill are threatened. You’ve likely seen pictures of these nineteenth- and twentieth-century row houses. They are among six thousand buildings in the city supported by such pilings, constituting 40 to 50 percent of the city’s residential tax base.

Here’s their history: When European settlers first arrived in this area, much of modern-day Boston was underwater. As the city expanded, it filled parts of Massachusetts Bay with soil, sand, and gravel. To build on such an unstable surface, builders drove tree trunks into the fill until they hit firmer ground, then placed foundation stones on top of these woodpiles.

This technique was used until the 1920s. Such wooden piles
can remain intact for hundreds of years if covered by groundwater, as they were
when they were first installed. However, as the city has grown, construction of
tunnels, sewers, basements, and subways has caused the groundwater level to
drop in many areas.

This exposes the tops of the pilings, then air causes them
to rot. The foundation stones then sink, as do the structures they support.

This story, however, is not just about architecture—it’s
also about human nature.

Repairing the wood pilings can be enormously expensive.
Buildings with pilings damage also sell for a significant discount. If owners
learn that their homes are at risk, they are obligated to say so if asked by
potential buyers. Testing the pilings can be intrusive and expensive as well.

An experienced building inspector can often locate signs of
rotted pilings, but many…