When a structure evidences displacement, often the first engineer on-site is a geotechnical engineer. The role of the geotechnical engineer is to identify sub-surface condition(s) which could contribute to or facilitate structural distress. The geotechnical engineer is then tasked with providing subsurface remediation recommendations when required. It is then the role of a structural engineer to assess the structure so as to diagnose the extent of damage and resulting distress. The structural engineer is then tasked with providing structural remediation recommendations when required. This may or may not include the implementation of structural underpins.

Structural underpinning is the process by which an existing foundation system is supplemented to restore support to the foundation, stabilize the foundation, or prevent potential future movement from occurring. Structural underpinning is a structural repair, and therefore should be specified by a licensed structural engineer. While the geotechnical engineer may recommend the use of structural underpinning within his recommendations, the design, location, and specification of structural underpins should be completed by the structural engineer.

It is important to note that Chapter 18 of the 2004 Florida Building Code states:

1808.2.21 Pier or pile location plan. A plan showing the location and designation of piers or piles by an identification system shall be filed with the building official prior to installation of such piers or piles. Detailed records for piers or individual piles shall bear an identification corresponding to that shown on the plan.

It should also be noted that the Florida Administrative Code Rules Chapter 61G15, which governs the practice of engineering in the state of Florida, states that foundation design shall be part of structural engineering plans.

61G15-31.008 Design of Foundations. (1) The structural engineering documents shall designate the foundation capacity and shall include data indicating the nature of the foundation material anticipated. (2) Site preparation requirements, necessary to provide the foundation capacity, shall be specified in the structural engineering document(s). (3) The foundation capacity shall be determined on the basis of scientific analysis utilizing investigations, tests or studies conducted or provided by the engineer of record for the structure or by a delegated engineer.

Therefore, in the end structural underpins may be recommended by a geotechnical engineer; but the specification of the system used and the location or attachments to the structure should be completed by a structural engineer.

If you would like information on structural underpinning, our Structures Group is ready to assist you. Please contact Tim Roda at troda@brackenengineering.com.

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