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B-44 Geotechnical Guidelines for Fire Rebuilds

The following guidelines are provided to clarify geotechnical reporting, observation, and testing requirements specific to foundations proposed to be located in areas where previous foundations and underlying contaminated soils have been removed due to fire exposure.

Effective date:  02/15/2018

Technical Details

Where new or rebuilt foundations are constructed in the footprint where fire damaged foundations have been removed, a geotechnical report is required to review the effects of foundation and soil removal as a result of debris cleanup. In lieu of a complete geotechnical report that addresses all potential hazards, per Section 1803 of the California Building Code, an abbreviated report by a civil engineer may be submitted to specifically address the effects of ground disturbance to the proposed foundation bearing surface and adjacent slope stability due to the removal of the foundation and underlying soil, and disturbances to adjacent slopes due to the burning of vegetation, debris removal adjacent to slopes, or other factors that may negatively impact slope stability.

The report shall include the following:

  • previous foundation type
  • suitability of the previous foundation type to current code requirements
  • required soil compaction percentage
  • suitability of onsite material to be used as fill
  • sub drainage requirements within the fill placement
  • depth of disturbed soil
  • depth below disturbed soil to an adequate bearing surface
  • foundation bearing capacity (on fill or undisturbed soil)
  • locations where soil was affected by debris removal

Where voids caused by removal of foundations and contaminated soil have been filled prior to submission of building plans, soil compaction reports (identifying results of relative compaction of fill placement) and laboratory testing data (justifying maximum dry density of fill material) shall be submitted with the Building Permit submittal package.

Situations may occur, including hazards uncovered in the abbreviated geotechnical report, changes in the proposed foundation type from the previous construction, or a significant increase in building loads from the original construction which may result in the requirement for a full geotechnical report, addressing all requirements of CBC Section 1803.

Where new or rebuilt foundations are placed outside of the original footprint the standard soils investigation requirements in Technical Bulletin B-28 When is a Soils Investigation Required? shall apply.


  • 2016 California Building Code
  • 2016 Sonoma County Code

Contact Information

2550 Ventura Avenue
Santa Rosa, CA 95403
38.465074, -122.723705