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Safety Cue
Task-specific safety guidance for ordinary aggregate-placement and barrier-installation hazards.
Project 07
Install Gravel Base and Vapor Barrier
Install a level, compacted aggregate base and a continuous vapor barrier over the Project 06 subgrade, using the approved aggregate type, compacted thickness, finished elevation, vapor-barrier rating, seam overlap, and penetration details, producing a compacted aggregate base and continuous protected vapor barrier ready for the next operation.
Field Cue System
These cues appear at the point of work. They identify safety, code, documentation, and dimensional issues before aggregate placement or vapor-barrier installation conceals the subgrade or compromises the barrier's continuity.
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Critical Safety Cue
A condition that must stop aggregate placement or barrier work until corrected and reverified.
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Field Safety Cue
Practical work-area safety around compaction equipment, aggregate stockpiles, and confined pad areas.
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Code Alert
Local requirements vary. Verify aggregate, vapor-barrier rating, and inspection rules.
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Manufacturer Cue
Follow product-specific instructions for vapor-barrier seaming, penetration sealing, and patching.
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Measurement Cue
Aggregate thickness, seam overlap, and elevation guidance for accurate, reproducible results.
Job Overview
This project qualifies you to install a level, compacted aggregate base and a continuous, sealed vapor barrier over the subgrade prepared in Project 06, using approved aggregate, controlled lift placement, compaction equipment matched to the aggregate and work area, and a vapor barrier installed, lapped, sealed, and penetrated according to the project detail. The finished work product is a compacted aggregate base at the specified thickness and elevation, and a continuous vapor barrier with sealed seams and penetrations, free of tears, punctures, and bridging, that is fully documented and photographed before concealment.
You will verify the Project 06 subgrade has passed inspection; review the required aggregate type, compacted thickness, finished elevation, vapor-barrier rating, seam overlap, and penetration details; spread and compact aggregate in uniform lifts; fine-grade the surface so it will not puncture the barrier; place, lap, and seal the vapor barrier; terminate it at edges and penetrations; repair any damage; and document the completed assembly before it is concealed by reinforcement, forms, or concrete.
This is the seventh project in the site preparation sequence. It begins with the inspected, protected subgrade produced in Project 06, and it does not authorize disturbing that subgrade's elevation or the Project 03 layout controls preserved through it. The compacted base and sealed vapor barrier produced here become the surface on which reinforcement, forms, and concrete are placed in later foundation and slab work, and the elevation reference used in Project 11.
Skills You Will Demonstrate
- SP-037 — Spread approved aggregate in uniform lifts within the specified compacted thickness over the Project 06 subgrade.
- SP-038 — Compact the aggregate base using equipment appropriate to the aggregate and work area, verifying elevation, thickness, and plane at regular intervals.
- SP-039 — Maintain required aggregate thickness and correct high, low, loose, or contaminated areas before the vapor barrier is placed.
- SP-040 — Install the vapor barrier in the manufacturer-controlled orientation, lapping and sealing seams using the approved method.
- SP-041 — Seal pipe, conduit, and other penetrations using compatible accessories, and repair tears, punctures, and damaged seams using the approved patch method.
- SP-042 — Inspect and document the completed aggregate base and vapor-barrier assembly for continuity, seam adhesion, and penetration seals before concealment.
Where This Skill Fits
Project 06 produced a compacted, verified subgrade at the required elevation, free of organic material, debris, and standing water, with a completed compaction record. That subgrade, and the Project 03 benchmark it preserves, control this project. Aggregate is placed to bring the surface to the finished base elevation required by the plan; where the Project 06 subgrade already sits at the required base elevation for a portion of the work, the aggregate steps in this project may be minimal in that area, but the vapor-barrier installation and inspection steps still apply in full.
The compacted base and sealed vapor barrier produced here become the working surface for the slab building pad in Project 11 and the surface concealed by reinforcement, forms, and concrete in the foundation work that follows. A puncture, unsealed seam, or thickness deficiency missed here is not caught again until the pre-inspection review in Project 16, by which time it is concealed under concrete.
Scope and Intended Use
This project covers:
- verifying the Project 06 subgrade has passed inspection and remains protected before aggregate is staged
- reviewing the required aggregate type, compacted thickness, finished elevation, vapor-barrier rating, seam overlap, and penetration details before work begins
- inspecting the work area for mud, debris, sharp objects, standing water, and damaged grade controls
- establishing final base elevation references and staging aggregate without overloading or rutting the subgrade
- spreading and compacting aggregate in uniform lifts within the specified thickness, checking elevation, thickness, plane, and edge conditions at regular intervals
- correcting high, low, loose, or contaminated areas and completing required compaction verification
- fine-grading the surface so it will not puncture or bridge the vapor barrier
- placing the vapor barrier in the manufacturer-controlled orientation, lapping and sealing seams, and extending and terminating the barrier at edges according to the project detail
- sealing penetrations using compatible accessories and repairing tears, punctures, and damaged seams using the approved patch method
- protecting the barrier with controlled access routes and approved supports, and inspecting and documenting continuity, seam adhesion, penetration seals, and surface damage before concealment
This project does not authorize the learner to:
- place aggregate over a subgrade that has not passed the Project 06 inspection, or over any area showing damage, contamination, or standing water since that inspection, without first obtaining direction
- compact an aggregate lift thicker than the specified loose thickness, or skip the required compaction verification, to save time
- place the vapor barrier in an orientation, lap width, or seam method other than the one specified by the manufacturer or the project detail
- leave a known tear, puncture, unsealed seam, or unsealed penetration in the barrier before it is concealed by reinforcement, forms, or concrete
- disturb, relocate, or re-square any Project 03 control point or Project 06 benchmark while placing aggregate or installing the vapor barrier
- proceed past a stop-work condition, such as a failed compaction verification or an unresolved barrier defect, without the direction of the responsible party
Any condition requiring a revised aggregate specification, a different vapor-barrier product, an engineer's determination, or a decision outside the approved base and barrier plan must be escalated before work proceeds in that area.
Reference Conventions
Use these references, established in Projects 01 through 06, throughout this project. Do not redefine them.
| Term | Definition |
|---|---|
| Aggregate base | The compacted layer of approved stone placed over the subgrade to the required thickness and elevation |
| Benchmark | The fixed elevation reference established in Project 03 and carried forward through Project 06, used to control aggregate and finished-base elevation in this project |
| Vapor barrier | The continuous sheet material installed over the aggregate base to restrict moisture movement into the slab or foundation assembly |
| Lap | The overlap between adjacent vapor-barrier sheets at a seam, measured to the width required by the manufacturer or project detail |
| Penetration | Any pipe, conduit, or other item passing through the plane of the vapor barrier, requiring a sealed boot or collar |
| Bridging | A condition where the vapor barrier spans a void or depression without full contact with the aggregate surface, increasing puncture risk |
Aggregate Base and Vapor Barrier Record
Before aggregate enters the work area, record the following:
Subgrade inspection confirmed passed: ______ Benchmark elevation confirmed: ______ Aggregate material inspected and approved: ______
Vapor-barrier product and rating confirmed: ____________ Date started: ____________ Builder name: ____________
Prerequisites
- Completed Project 06 compaction record, with the subgrade inspected and declared ready, protected since inspection, and the Project 03 benchmark confirmed
- Required aggregate type, compacted thickness, finished elevation, vapor-barrier rating, seam overlap, and penetration details reviewed before aggregate is staged
- Approved aggregate sourced and available in sufficient quantity to reach the specified base elevation across the full work area
- Vapor-barrier product, seam-sealing method, and penetration accessories confirmed against the manufacturer's instructions before installation
- Identification of the party authorized to approve a revised aggregate specification, evaluate a failed compaction verification, or accept a barrier repair
Common Field Fundamentals
Aggregate base and vapor-barrier installation convert the inspected Project 06 subgrade into the finished working surface for reinforcement, forms, and concrete, without losing the benchmark and dimensions that control every later chapter. A compaction deficiency, thickness error, or barrier defect missed here is not caught again until the pre-inspection review in Project 16, by which time it is concealed.
Plan reviewAggregate type, thickness, barrier rating, seam overlap
Area inspectionMud, debris, sharp objects, standing water
Aggregate placementUniform lifts within specified thickness
CompactionEquipment matched to aggregate and area
Fine-gradingSurface free of points that puncture or bridge barrier
Barrier placementManufacturer-controlled orientation and lap
SealingSeams and penetrations sealed per approved method
DocumentationPhotographed before concealment
Working From the Verified Subgrade
Every aggregate and barrier action in this chapter is controlled by the benchmark and dimensions verified in Project 03 and re-confirmed through Project 06. Recheck the benchmark at Step 4 of this project before establishing final base elevation references. If a field condition suggests the required base elevation should be adjusted, stop and obtain direction before placing aggregate; do not raise or lower the base to compensate for a subgrade discrepancy discovered during this project.
SP-037 – SP-042
Aggregate Base and Vapor Barrier Qualification
Compacted Aggregate Base and Sealed Vapor Barrier
A. Finished-Deliverable Specification
Deliverable: one compacted aggregate base built over the Project 06 subgrade from approved aggregate spread in uniform lifts within the specified thickness, compacted with equipment suited to the aggregate and work area, verified for elevation, thickness, and plane at regular intervals, and fine-graded to prevent puncture or bridging; and one continuous vapor barrier placed in the manufacturer-controlled orientation over that base, with seams lapped and sealed to the approved method, penetrations sealed with compatible accessories, tears and damaged seams repaired using the approved patch method, and the completed assembly protected, inspected, and photographed before concealment.
B. Aggregate Base and Vapor Barrier Deliverable Schedule
| Item | Quantity | Form | Content Requirement | Purpose |
|---|---|---|---|---|
| Compacted aggregate base | Full work area, to specified thickness | Spread and compacted lifts | Meets the project's aggregate specification; compacted to the specified thickness, elevation, and plane | Providing a level, stable, puncture-resistant surface for the vapor barrier |
| Vapor barrier | Full work area, continuous | Installed sheet material | Correct manufacturer-specified orientation; seams lapped and sealed to the approved method | Restricting moisture movement into the slab or foundation assembly |
| Sealed penetrations | Each penetration present | Boots, collars, or compatible accessories | Sealed per manufacturer instructions with no gap around the penetrating item | Preserving barrier continuity at pipe, conduit, and other penetrations |
| Repaired damage | As found | Patched tears, punctures, or seams | Repaired using the approved patch method and re-verified | Restoring full continuity before concealment |
| Completed installation record | 1 record set | Written record and photographs | Aggregate thickness, elevation, compaction results, barrier product, seam and penetration details, and repairs recorded | Documenting the completed assembly for the Project 11 and Project 16 inspections |
C. Material Takeoff
- Approved aggregate: sufficient volume to reach the specified compacted thickness and finished elevation across the full work area, meeting the project's aggregate specification.
- Vapor barrier: sufficient sheet material to cover the full work area continuously, including the lap width required at every seam and the extension required at every edge and termination.
- Seam tape or approved sealing method: sufficient quantity for every seam, penetration, and anticipated repair, matching the vapor-barrier manufacturer's compatibility requirement.
- Pipe and penetration boots or collars: sufficient quantity for every penetration present in the work area.
- Patch material: sufficient quantity to repair tears, punctures, and damaged seams identified during installation or inspection.
- Waste allowance: the material quantities above are working allowances; record any material used beyond the planned quantity, and the reason, on the installation record.
D. Acceptance Standards
| Check | Standard |
|---|---|
| Aggregate material | Matches the project's aggregate specification; free of contamination and unsuitable material |
| Aggregate thickness | Meets the specified compacted thickness at every checked point |
| Base elevation and plane | Matches the approved plan elevation, verified against the Project 06 benchmark; surface free of high or low spots that could puncture or bridge the barrier |
| Vapor-barrier orientation and lap | Installed in the manufacturer-specified orientation; seams lapped to the specified minimum width |
| Seam and penetration seals | Continuous adhesion at every seam; every penetration sealed with a compatible boot or collar and no visible gap |
| Barrier condition | Free of tears, punctures, and unrepaired damage before concealment |
| Documentation | Aggregate thickness, elevation, compaction results, barrier product, seam and penetration details, and repairs recorded and photographed before the Project 11 and pre-inspection reviews |
E. Preparation — Subgrade Verification and Specification Review
- Verify that the subgrade has passed inspection and is protected from damage. Confirm the Project 06 compaction record shows a passed inspection and inspect the surface for damage since that inspection.
- Review required aggregate type, compacted thickness, finished elevation, vapor-barrier rating, seam overlap, and penetration details. Confirm these values against the current project specification and manufacturer instructions before aggregate is staged.
- Inspect the work area for mud, debris, sharp objects, standing water, and damaged grade controls. Walk the full work area and identify every condition inconsistent with a sound aggregate base or barrier installation.
F. Aggregate Placement and Compaction
- Establish final base elevation references. Mark aggregate-thickness and finished-elevation references from the Project 06 benchmark before the first lift is spread.
- Deliver and stage aggregate without overloading or rutting the subgrade. Place delivered aggregate outside the immediate spreading area to avoid concentrated loading on the subgrade.
- Spread aggregate in uniform lifts within the specified thickness. Distribute aggregate evenly across the work area to the marked thickness reference.
- Compact each lift with equipment appropriate to the aggregate and area. Select and operate compaction equipment matched to the aggregate gradation and the confined dimensions of the work area.
- Check elevation, thickness, plane, and edge conditions at regular intervals. Measure the compacted surface against the benchmark and inspect edges and corners for consistent thickness and plane.
- Correct high, low, loose, or contaminated areas. Add, remove, or recompact aggregate at any location that fails the elevation, thickness, or plane check.
- Complete required compaction verification. Perform or arrange the density, proof-roll, or other verification method identified by the project specification.
G. Vapor-Barrier Placement and Sealing
- Fine-grade the surface so it will not puncture or bridge the vapor barrier. Remove or bed any protruding stone, sharp edge, or depression identified across the compacted base.
- Place the vapor barrier in the manufacturer-controlled orientation. Roll out the barrier across the prepared base in the orientation specified by the manufacturer's instructions.
- Lap and seal seams using the approved method. Overlap adjacent sheets to the specified minimum width and seal using the manufacturer-specified tape or sealing method.
- Extend and terminate the barrier at edges according to the project detail. Carry the barrier to the required edge extension and terminate it using the method specified in the project detail.
- Seal pipe, conduit, and other penetrations using compatible accessories. Fit and seal a boot or collar compatible with the barrier product around every penetration present in the work area.
H. Repair, Protection, and Inspection
- Repair tears, punctures, and damaged seams using the approved patch method. Patch every identified defect using material and a method compatible with the installed barrier, then re-verify the repaired area.
- Protect the barrier with controlled access routes and approved supports. Establish walk paths and material-staging supports that avoid unnecessary traffic across the installed barrier.
- Inspect continuity, seam adhesion, penetration seals, and surface damage. Walk the completed assembly and confirm every seam, penetration, and repaired area meets the Acceptance Standards table.
- Photograph and document the completed assembly before concealment. Complete the installation record with every required entry and photograph the assembly from fixed reference points before reinforcement, forms, or concrete work begins.
Common Site Inspection
Inspect the completed aggregate base and vapor barrier using the same checks regardless of pad size or barrier product.
- Aggregate check: confirm placed aggregate matches the project specification and is compacted to the specified thickness, elevation, and plane.
- Surface check: confirm the compacted base is free of protruding stone, loose material, and depressions that could puncture or bridge the barrier.
- Orientation and lap check: confirm the vapor barrier is installed in the manufacturer-specified orientation with seams lapped to the required minimum width.
- Seal check: confirm every seam, edge termination, and penetration is sealed per the manufacturer's instructions and the project detail.
- Damage check: confirm the barrier is free of unrepaired tears, punctures, or damaged seams.
- Documentation check: confirm the installation record, compaction results, and photographs are complete.
Complete the Aggregate Base and Vapor Barrier Record Sheet in the Inspection Checklist section below before this surface is concealed.
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Failure Points and Troubleshooting
Cleanup
This project ends with a compacted aggregate base and sealed vapor barrier left in place and protected, not a surface that has already been covered by reinforcement, forms, or concrete.
- Confirm protected access routes and supports remain in place over the completed vapor barrier
- Confirm every Project 03 control point and Project 06 benchmark remains flagged, protected, and reflects its recorded location
- Remove surplus aggregate, barrier scrap, packaging, and tools from the work area and equipment routes
- Confirm the completed assembly remains clean, undamaged, and free of standing water
- File the completed installation record, compaction results, and photographs with the Project 01 through 06 records
Field Terms
- Aggregate Base
- The compacted layer of approved stone placed over the subgrade to the required thickness and elevation.
- Vapor Barrier
- The continuous sheet material installed over the aggregate base to restrict moisture movement into the slab or foundation assembly.
- Lap
- The overlap between adjacent vapor-barrier sheets at a seam, measured to the width required by the manufacturer or project detail.
- Penetration
- Any pipe, conduit, or other item passing through the plane of the vapor barrier, requiring a sealed boot or collar.
- Bridging
- A condition where the vapor barrier spans a void or depression without full contact with the aggregate surface, increasing puncture risk.
- Permeance Rating
- The manufacturer-stated resistance of the vapor barrier to moisture-vapor transmission.
- Boot or Collar
- A manufactured accessory used to seal the vapor barrier around a pipe, conduit, or other penetration.
- Proof-Roll
- A verification method using loaded equipment passes to identify soft or unstable areas in a compacted surface.
- Stop-Work Condition
- A field condition requiring work to halt until a competent person, engineer, or responsible party provides direction.
Skill Check
- Why must the Project 06 subgrade inspection status be confirmed before aggregate is delivered to the work area?
- Why is the aggregate surface fine-graded before the vapor barrier is placed?
- What happens to a seam's protection if it is lapped less than the manufacturer's specified minimum width?
- Why must a penetration be sealed with a compatible boot or collar rather than only taped in place?
- What must the learner do before reinforcement, forms, or concrete is allowed to conceal a repaired area of vapor barrier?
- Why must compacted aggregate elevation be checked against the Project 06 benchmark rather than by visual estimate?
- What is the difference between the aggregate thickness check performed here and the lift-thickness check performed in Project 06?
- Why must access routes across the installed vapor barrier be controlled before concealment?
- What must be recorded for the completed aggregate base and vapor-barrier assembly before this project closes?
- What must be completed before this surface is released for reinforcement, forms, or concrete work?
Competency Rubric
| Competency | Independent Pass Standard | Not Demonstrated | With Assistance | Independently |
|---|---|---|---|---|
| SP-037 | Spreads approved aggregate in uniform lifts within the specified compacted thickness over the Project 06 subgrade | |||
| SP-038 | Compacts the aggregate base using equipment appropriate to the aggregate and work area, verifying elevation, thickness, and plane at regular intervals | |||
| SP-039 | Maintains required aggregate thickness and corrects high, low, loose, or contaminated areas before the vapor barrier is placed | |||
| SP-040 | Installs the vapor barrier in the manufacturer-controlled orientation, lapping and sealing seams using the approved method | |||
| SP-041 | Seals pipe, conduit, and other penetrations using compatible accessories, and repairs tears, punctures, and damaged seams using the approved patch method | |||
| SP-042 | Inspects and documents the completed aggregate base and vapor-barrier assembly for continuity, seam adhesion, and penetration seals before concealment |
Mark one column per competency. Only Demonstrated Independently awards the competency; Demonstrated with Assistance authorizes additional supervised practice but does not complete the requirement.
Inspection Checklist — Aggregate Base and Vapor Barrier Record Sheet
| Item | Approved / Specified Value | Field Result | Within Requirement (Y/N) | Correction (if any) |
|---|---|---|---|---|
| Aggregate material compliance | ||||
| Aggregate compacted thickness | ||||
| Finished base elevation and plane | ||||
| Vapor-barrier orientation and lap | ||||
| Seam and penetration seals | ||||
| Barrier condition (tears/punctures) |
Escalations and direction obtained (list): ____________ Unresolved conditions: ____________
Assembly declared ready for concealment: ______ (Yes/No) Date: ____________ Builder name: ____________
Performance Check
With aggregate spread, compacted, and verified, and the vapor barrier placed, lapped, sealed, and penetration-sealed, review the completed assembly against the Acceptance Standards table and confirm the aggregate material matches the project specification, the compacted thickness and finished elevation match the approved plan against the Project 06 benchmark, the vapor barrier is installed in the correct orientation with seams lapped to the required minimum width, every seam and penetration is sealed with no visible gap, the barrier is free of unrepaired tears or punctures, and the installation record and photographs are complete. Complete the Aggregate Base and Vapor Barrier Record Sheet and correct any failed item before this surface is concealed.
Project Closeout
You have completed the seventh project in the site preparation sequence: converting the inspected Project 06 subgrade into a compacted aggregate base with a continuous, sealed vapor barrier. This project required you to spread approved aggregate in uniform lifts within the specified compacted thickness (SP-037), compact the base using equipment appropriate to the aggregate and work area while verifying elevation, thickness, and plane (SP-038), maintain required thickness and correct high, low, loose, or contaminated areas (SP-039), install the vapor barrier in the manufacturer-controlled orientation with lapped and sealed seams (SP-040), seal penetrations with compatible accessories and repair tears, punctures, and damaged seams using the approved patch method (SP-041), and inspect and document the completed assembly for continuity, seam adhesion, and penetration seals before concealment (SP-042).
You now have a compacted, protected aggregate base and sealed vapor barrier that supports the slab building pad work in Project 11 and the foundation work that follows it.
Leave your vapor barrier sealed, your installation record complete, and your benchmark and control points undisturbed. Later projects place reinforcement, forms, and concrete directly on the surface established here.