How do you build a residential foundation in Fairbanks, Alaska? The answer depends on site conditions — especially soil conditions and the presence or absence of permafrost. The answer may also depend on whether or not you think the climate is warming. Juggling all these factors is tricky, which is why some Fairbanks builders who followed best practices for foundation design ended up with buildings that are now leaning or sinking.
From a construction viewpoint, Fairbanks has terrible soils. Some neighborhoods are underlain by permafrost that is hundreds of feet thick; in these areas, only the top few feet of soil ever thaw. Other sites formerly had stable permafrost — permafrost which is now melting. Still others never had permafrost — they just have unstable soils that are tricky to build on.
Even builders who have sought the advice of engineers have learned the hard way that an expensive foundation won’t always keep you out of trouble.
If you drive through certain Fairbanks neighborhoods, you’ll see lots of examples of buildings that appear to have sunk or settled unevenly. There is no single explanation for all of these foundation failures; each failure is unique. But taken together, these failures represent a cautionary tale for foundation designers.
According to a 2017 news article by Emily Gertz on a web site called News Deeply, “Soils in Alaska’s second-largest city are marred by discontinuous permafrost. They’re unpredictable and dynamic and they shift and change, sometimes dramatically from season to season. … ‘There’s a lot of bad things happening with soils,’ said [structural engineer Tim] Henry. ‘I mean, compared to just four or five years ago, there’s a lot more [problems]. Seeing the properties that have been there for a long time and then move after 20 years, that’s real scary, because no…