Geotechnical special inspection is one of the most consequential inspection programs on any building project. It covers the ground conditions that determine whether a structure stands or settles — and the documentation requirements under IBC Chapter 17 are detailed, specific, and mandatory for certificate of occupancy. This guide covers what records are required, who must create them, and how to structure a geotechnical special inspection package that closes without re-inspection.
What records does geotechnical special inspection require?
Geotechnical special inspection documentation requires five categories of records: fill placement records (lift thickness, compaction results, material source per lift); bearing capacity verification for spread footings (depth, bearing material, field bearing tests); driven pile installation logs (blow count, driving resistance, final set, tip elevation per pile); drilled pier logs (diameter, depth, bearing stratum, concrete placement); and a final report signed by the geotechnical engineer certifying conformance with the soils report. All records must be retained and submitted to the building department before certificate of occupancy.
IBC Chapter 17 establishes the framework for special inspection on building projects. Section 1705.6 identifies geotechnical work as a category requiring special inspection on most commercial projects. The engineer of record specifies which geotechnical inspection categories apply in the Statement of Special Inspections, which is submitted with the building permit application and approved by the building official before construction begins.
The inspection categories most commonly triggered on commercial projects include:
| Work Category | Inspection Type | Key Documentation |
|---|---|---|
| Controlled fill placement | Periodic or continuous | Lift-by-lift compaction logs, elevation shots, material certifications |
| Spread footing bearing | Periodic | Bearing depth, material classification, field bearing test where specified |
| Driven piles and caissons | Continuous | Per-pile driving log: blow count, final set, tip elevation, pile ID |
| Drilled piers / CIDH piles | Continuous | Diameter, depth, bearing stratum, cage depth, concrete placement log |
| Helical piles | Periodic or continuous | Installation torque, depth, final capacity calculation per pile |
| Retaining wall backfill | Periodic | Compaction tests at specified frequency, elevation verification per lift |
Controlled fill documentation is the most common geotechnical special inspection task on building projects. It applies any time imported or recompacted material is placed as a structural fill beneath building footings, slabs-on-grade, or paved areas subject to structural loads.
Required records for each lift of controlled fill:
Use the Elevation Calculator to compute and verify fill surface elevations from your rod shots at each lift. Confirming elevations before backfilling keeps your documentation in sequence with the work.
Driven pile installation logs are among the most detailed records in geotechnical special inspection. Continuous inspection is required throughout driving, and the inspector must document each pile individually.
Required data on each driven pile installation log:
Unique pile ID matching the structural drawing designation — no generic numbering
H-pile section, pipe pile diameter and wall thickness, prestressed concrete section designation
Start and completion time for each pile; continuous inspection requires inspector presence throughout
Hammer type, model, rated energy (ft-lb), cushion type, and driving cap description
Blows per foot for the full driving depth; blows per inch for final set determination
Final tip elevation (NAD83 or project datum); as-driven cutoff elevation; embedment depth
Blows per inch at final driving — compared to contract specification for pile capacity acceptance
Any splice, splice location, refusal, restrike, or deviation from plan must be documented and reported
Drilled pier (cast-in-drilled-hole or CIDH pile) inspection requires continuous inspector presence during drilling, cleaning, rebar cage installation, and concrete placement. The inspection log must document each of these phases separately for every pier.
| Phase | Required Documentation |
|---|---|
| Drilling | Start time, drilled diameter, depth drilled vs. design depth, boring log with stratum descriptions at each change |
| Bottom cleaning | Method used, sump depth (should be less than 2 inches for dry holes), inspector observation of bearing stratum |
| Rebar cage | Cage length, bar size and spacing verified against approved shop drawing, cover blocks or centralizers installed |
| Concrete placement | Tremie or pump method, concrete mix design number, slump test results, number of yards placed, top-of-concrete elevation after placement |
| Final survey | As-built top-of-pier elevation, plan coordinates, plumbness (deviation from vertical), cutoff elevation |
IBC Section 1705.2 requires that special inspectors submit a final report to the building official prior to issuance of the certificate of occupancy. For geotechnical special inspection, this final report must:
Building departments will not issue the certificate of occupancy until the final special inspection report is on file. Missing or incomplete reports are one of the most common reasons project closeouts are delayed.
Sitemark captures compaction test results, pile driving logs, and pier records in real time — generating the final inspection report package ready for building department submission.
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Shop at Express Tools →Geotechnical special inspection documentation requires fill placement records (compaction logs, lift thickness, material source), bearing capacity verification for footings, driven pile installation logs (blow count, final set, tip elevation), drilled pier logs (depth, stratum, concrete placement), and a final report signed by the geotechnical engineer certifying conformance. All records are required for certificate of occupancy.
Inspectors must be approved by the building official. Typical qualifications include ICC Soils Special Inspector certification, a state professional engineering license, or employment by the geotechnical engineering firm of record. The Statement of Special Inspections must identify the inspection agency and individual inspector qualifications.
IBC Table 1705.6 triggers geotechnical inspection for controlled fill over 12 inches deep, driven deep foundations, drilled piers, helical piles, and footings on compressible soils. The engineer of record identifies applicable categories in the Statement of Special Inspections submitted with the permit application.