Adaptive Foundation Design

By Nancy Nichols, P.E. | June 22, 2022

This project is referred to as The Needles (after the original hunting lodge owner, I think).  When I first inspected under the building’s crawl space (tight squeeze), I had to mobilize (a.k.a. squirm) around a large tree trunk andlimbs, and push aside piles of leaves and other organic debris in order to see what was holding up this historic and loved lakeside retreat.

It was found that the foundation, consisting of various types of shallow piers, was bearing on soft soils.  It appears that the building was occupying a former wet area and the footings had been settling/sinking at uneven rates for generations.  After the left side of this building had been struck by parts of a large falling tree during a windstorm (see blue tarp), it was decided that the foundation should be improved during its reconstruction.

The owners wished to retain the aesthetics of the old hunting lodge as much as possible while installing a sound foundation.  The design of the foundation had to consider the depth of soft soils (up to about 8 ft.) and shallow groundwater (about 2 ft. below ground surface).  Groundwater this shallow has high vapor pressure above it.  Any foundation design needed to consider that without high ventilation, condensation, mold and rot would be inevitable.

Team Engineering designed a foundation of end-bearing helical piers supporting concrete grade beams at ground surface.  The modified post & beam superstructure and grade beams were aligned to maximize ventilation.  There are large gaps between the ends of concrete grade beams.   Moreover, the 1st floor wood beams will bear on spaced studs on the concrete grade beams to allow ventilation between the bottom of the 1st floor framing and top of the grade beams.  This utilizes the leveling of the floor above the sloping ground surface to an advantage.

We greatly appreciate the trust of these owners to design and implement a foundation that is not only structurally sound, but also provides for a healthy indoor environment and durability of the structre for another 100 years or more.

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