How to Document a Pile Driving Log for Foundation Work

Applies to: driven steel H-piles, pipe piles, precast concrete piles, timber piles, helical piles with torque logging

Pile driving logs are permanent legal and structural records. They document the load-carrying capacity evidence for each foundation pile — the blow counts that the geotechnical engineer uses to evaluate whether the pile achieves design capacity. Incomplete or inaccurate pile logs can lead to rejected piles, additional load testing, and in worst cases, foundation remediation after the structure is built. Knowing how to keep a proper pile driving log is a critical field skill for any crew running a pile rig.

Step 1: Set Up the Log Header Before Driving Begins

Complete the pile log header before the hammer touches the pile. Required header fields:

Project name and address. Pile ID (from the pile plan drawing — each pile has a unique designation such as P-1, P-2, or a grid reference). Pile type (HP14x89, 16-inch open pipe pile, 14-inch square precast, etc.). Pile specified length and actual delivered length. Hammer identification: make, model, and serial number. Hammer rated energy (in foot-pounds or kJ). Cushion type and condition (for precast piles). Driving criteria: the blow count or set-per-blow value the geotechnical engineer requires for acceptance. Date, time driving began, and inspector name. Weather and site conditions at time of driving.

A log that is missing the hammer energy setting or driving criteria cannot be reviewed by the geotechnical engineer — they need to know what hammer was used to interpret blow counts in terms of soil resistance. If you do not have the hammer specifications, get them from the pile subcontractor before driving begins, not after.

Step 2: Record Blow Counts by Foot of Penetration

Record the number of hammer blows required to advance the pile each foot (or each 0.25m for metric projects). Starting from the ground surface (or from the point of initial hammer contact if the pile is pre-augered), count blows from 0 to 1 foot, 1 to 2 feet, 2 to 3 feet, and so on until the pile reaches final tip elevation.

Mark the pile in one-foot increments before driving — use paint, chalk, or tape. If the pile is not marked, it is impossible to accurately record blow counts per foot of penetration while the rig is running. The pile crew foreman should mark the pile before the rig positions over the pile hole.

Note any unusual events during driving at the depth where they occur: sudden increases in penetration rate (possible weak layer, void, or pile tip damage), sudden increases in blow count (cobbles, hard strata, obstructions), pile run (pile advancing under its own weight without hammer blows), or pile refusal (defined below). These observations are as important as the blow counts themselves for geotechnical interpretation.

Step 3: Record Driving Criteria and Final Set

Most driven pile acceptance criteria are specified as a required minimum blow count over the last foot of driving, or a set per blow (penetration per blow in the last 10 blows). Common criteria examples: "minimum 20 blows per foot over the last foot" or "set not to exceed 0.25 inches per blow in the last 10 blows."

When the pile approaches the anticipated final penetration depth, alert the inspector to watch closely. Record the blow count and set measurement at the last foot in detail. For set-per-blow criteria, measure the total penetration over the last 10 blows and divide by 10. Use a steel rule or tape held against the pile while driving to measure penetration per blow accurately.

Refusal is defined differently by project specifications — commonly when the pile fails to advance more than 0.25 inches per blow for 10 consecutive blows, or when blow counts exceed 100 blows per foot. Record the depth at which refusal occurs. Refusal before design tip elevation requires notification of the geotechnical engineer before continuing.

Step 4: Record Final Pile Dimensions and Elevations

After driving is complete, record: total driven length (from ground surface to pile tip), tip elevation (calculate from the known ground elevation at the pile location minus the driven depth), cutoff elevation (the elevation at which the pile will be cut to match the cap design), and stick-up length (distance the pile projects above the cutoff elevation).

Survey the pile cutoff elevation with a level or total station against the project benchmark. Do not calculate it solely from tape measurements — elevation errors from a misread tape propagate into the pile cap elevations and can result in rebar couplers at the wrong height. Record the surveyed cutoff elevation on the pile log.

Step 5: Submit Logs to the Geotechnical Engineer for Acceptance

Completed pile driving logs must be submitted to the geotechnical engineer of record for review and acceptance before the pile caps are poured. The geotechnical engineer will review blow counts against the soil boring logs and the design driving criteria to confirm each pile achieves adequate capacity.

Logs should be signed by the field inspector or the pile inspector of record. Many jurisdictions require a special inspector for all driven pile work — confirm inspection requirements before driving begins. Unsigned or incomplete logs are typically rejected and require reconstruction from field notes, which is difficult after the fact.

Gradelog field records can capture pile driving data in real time — blow counts by depth, hammer ID, criteria, and GPS location of each pile — producing formatted pile logs automatically at the end of each driving day.