New Hampshire Subsurface Conditions

By Nancy Nichols, P.E. | November 5, 2020

Shallow bedrock frequently occurs in New Hampshire.  Building on bedrock has its own challenges.  This photo is of an excavation for residential garage structure and breezeway.  The ground surface slopes down to the rear (foreground) and to the right (see photo) at large block retaining wall.  The bedrock surface rises and falls below the footprint and naturally drops at the retaining wall (pre-constructed).

A concrete foundation constructed on bedrock and soil will crack due to rapid transition from bearing surfaces of high (say 10,000 psf) to medium (say 2500 psf) bearing capacities.  Lean concrete can be used to level the bedrock surface.  Construction or control joints can be incorporated into the design to mitigate uncontrolled cracking.  Reinforcing steel can be incorporated at stem wall transitions.  Alternatively, higher walls of concrete can be constructed to bear fully on bedrock, but usually at a higher price tag.  Call us at Team Engineering to help you to limit foundation construction cracking and costs to repair them.

Leave a Comment

Your email address will not be published.