No construction projects on my plate right now. Colin’s house is very nearly complete, with a few finishing tasks that Terry will perform unassisted. Bob has a gorgeous upstairs to come home to; the rest of his house is on hold while he attends to some personal business. That means I can turn my attention fully to my nascent civil engineering practice, PERCH.

I have one client near Montpelier who plans to lift his existing house 7 feet while maintaining the foundation. The goal is to elevate all habitable parts of the structure above Base Flood Elevation, or BFE. I love this project because it’s the perfect marriage of engineering principles and construction reality.

Why was the house built below BFE? Well, it wasn’t. BFE is based on historical data, just like snow load and ground acceleration (i.e. earthquake strength). But how do you set a 500-year flood elevation when reliable data only go back a couple hundred years? You can use statistical models to estimate the likelihood that a future flood will surpass any flood on record, but the result feels a bit hand-wavey… like adding a random volume of water to the worst hurricane anyone can remember. Each passing year provides new recordings and makes the picture less blurry.

Irene, 2011. This actually happened. (picture from The Valley Reporter)

When Hurricane Irene blasted New England and upstate New York in 2011, it created a new historical data point. Though my client’s house weathered the storm just fine, the new data altered local flood insurance rate maps to reflect that a flood was more likely than previously thought. This change put the house underwater, so to speak, and threatened to increase the flood insurance premium by a factor of ten.

Instead, my client applied for and received a FEMA grant to bring the house back into compliance by elevating it a foot above BFE. And that’s where PERCH comes in!