What is a proof roll and how is it documented?

A proof roll is a visual inspection method where a heavy loaded vehicle — typically a fully loaded dump truck or tandem axle truck with a gross weight of 20 to 25 tons — is driven over the prepared subgrade in overlapping passes at low speed (3 to 5 mph). The inspector observes the surface for deflection, rutting, or pumping that indicates inadequate bearing capacity. Any area that deflects more than 1 inch under the wheel load, shows pumping or cracking of the surface, or where ruts do not spring back is flagged as a soft spot requiring remediation. The proof roll log records: date, equipment identification and loaded weight, coverage pattern, station and offset of each soft spot identified, and the inspector's name and signature.

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Subgrade Preparation Documentation: Proof Rolling and Inspection

Subgrade preparation documentation is the checkpoint between earthwork and pavement or slab construction. A missing or incomplete proof roll record is one of the most common reasons a DOT inspector stops paving operations — and once base course is placed over a soft spot, the documentation gap becomes a liability that can follow the project through its entire design life.

Published May 29, 2026·8 min read

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Quick Answer

What documentation is required for subgrade preparation and proof rolling?

Subgrade preparation documentation requires: compaction test results confirming specified percent compaction (typically 95% Modified Proctor for road subgrade); a proof rolling observation report identifying the equipment, loaded weight, observation area, and any soft spots by station and offset; soft spot remediation records including undercut depth, unsuitable material disposal, replacement fill specification, and post-replacement compaction tests; and a written subgrade acceptance from the engineer or inspector authorizing base course placement.

95% of Modified Proctor (AASHTO T180) for road subgrade

Typical compaction requirement

20–25 tons gross loaded weight (typically fully loaded dump truck)

Proof roll vehicle weight

>1 inch deflection under wheel load triggers remediation

Soft spot deflection limit

Compaction Testing Before Proof Rolling

Proof rolling is a visual supplement to compaction testing — it is not a substitute. The compaction test record must be produced before the proof roll begins. Required compaction documentation at subgrade:

Record	Content
Proctor test record	Material description, Proctor test method (AASHTO T99 or T180), maximum dry density, and optimum moisture content. Must reference the material source — typically the borrow pit or cut area being placed.
Field density test log	Date, test station and offset, depth tested, dry density result, moisture content, percent of maximum dry density, and pass/fail status. Test frequency is typically one per 500 LF of roadway or one per 1,500 SF for area projects.
Nuclear gauge calibration	Annual calibration record for the gauge used; operator certification document.
Failed test remediation	When a field density test fails, the remediation action (additional compaction passes, moisture conditioning, or partial removal and re-compaction) and re-test result must be documented.

Proof Rolling: Procedure and Documentation

A proof roll is a visual inspection method — not an instrumented test. The inspector observes the subgrade surface while a loaded vehicle makes systematic passes. Documenting the procedure and results:

Equipment identification. Record the equipment type, make, model, and loaded gross weight. Most DOT specifications require a fully loaded tandem axle dump truck with a gross weight of 20 to 25 tons. Confirm the vehicle is loaded to the required weight and document the weight ticket if available.
Coverage pattern. The vehicle must cover the entire subgrade area in overlapping passes — typically offset by one wheel width per pass. Document the pattern (longitudinal passes parallel to road alignment, or grid pattern for area paving). The inspector must observe every pass.
Speed. Passes must be made at 3 to 5 mph to give the inspector sufficient observation time. Record the approximate speed used.
Soft spot identification. Document each soft spot by station and offset (or grid coordinates for area paving), the failure type (rutting, pumping, cracking, or deflection without spring-back), the approximate area of the soft zone in square feet, and the inspector's recommendation for remediation.
Inspector name and signature. The proof roll report must be signed by the qualified inspector. On DOT projects, the proof roll must be witnessed by the owner's inspector — not just the contractor's QC personnel.

Soft Spot Remediation Documentation

Every soft spot identified during proof rolling must be remediated and documented before the subgrade is approved. Required remediation records:

Remediation Step	Documentation Required
Undercut extent determination	Depth of unsuitable material, area of removal, and identification of the unsuitable material type (organic, high plasticity clay, wet material)
Unsuitable material removal	Photo documentation of excavation; disposal record or disposal site confirmation
Replacement fill placement	Material specification (select fill, granular material, or geotextile with aggregate), source, and maximum lift thickness
Replacement compaction tests	Nuclear gauge test at each replaced area at the same frequency as original subgrade testing
Engineer acceptance	Written or documented verbal acceptance from the geotechnical engineer or project engineer before subgrade is re-proof-rolled

Subgrade Acceptance and Base Course Authorization

After all soft spots are remediated and re-proof-rolled, the subgrade acceptance document is prepared. This is the gate document that authorizes the paving or base course contractor to proceed. Required content:

Project name, location, and contract number
Date of subgrade acceptance inspection
Station limits or area description of accepted subgrade
Reference to compaction test log confirming density compliance
Reference to proof roll report and any soft spot remediation records
Statement of acceptance: "The subgrade between Station X and Station Y has been inspected and is accepted for base course placement"
Name and signature of the engineer or inspector authorizing the work

Sitemark's field documentation tools let earthwork teams log compaction test results, GPS-tag soft spots during proof rolling, and generate the subgrade acceptance package that the paving superintendent needs to schedule the base course crew.

Subgrade Documentation That Keeps Paving on Schedule

Sitemark captures compaction test logs, proof roll soft spot locations, and remediation records in a linked package — so subgrade acceptance sign-off is ready when the base course crew arrives.

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