What is Frost Jacking?

If you own or manage a building in NYC, you probably are (or should become) familiar with frost jacking.

Whenever it rains or snows, water seeps into crevices, pores, and even micro-cracks in building facades and parapets. Unlike other liquids, water expands when it freezes. Cycles of precipitation at temperatures above freezing followed by temperatures below freezing expand the sizes of cracks, in a phenomenon known as "frost jacking." As buildings age, these expanded cracks can result in hazardous facade conditions, or become the source of leaks into the building interior.

Our Tracker

Since 2017, SUPERSTRUCTURES has maintained a resource called the Frost Jacking Day Tracker. It is updated every month between December and April of each year, to help building owners understand the effect New York City's frost jacking cycles are having on their properties.

We use data provided to the National Weather Service by the weather station in Central Park. Since water freezes at 32 degrees F, we look for days where the minimum temperature is 30 degrees F or lower preceded by days where the maximum temperature is 33 degrees F or higher, with rain and/or snow one or two days before.

Taller buildings and buildings closer to the coast will likely experience more frost jacking days. Similarly, persistent snow at a roof parapet, window ledge, or terra cotta water table may cause frost jacking as the snow melts and refreezes.

The "last inspection/repair" noted in the chart above might be the most recent critical examination date for a building subject to FISP, or the date of completion of a facade repair campaign. The cumulative number of frost jacking days isn't a precise indicator of facade behavior: there are other variables such as age, condition, orientation, materials of construction, etc. But it may help you understand why your building may be experiencing new problems and why it needs to be periodically inspected.