CSLB C-27 Landscaping ContractorHardscape and FeaturesHard
A landscape contractor is installing a series of large, heavy precast concrete pavers for a high-traffic walkway. To prevent differential settling and ensure a durable, level surface over many years, which base preparation method is most critical before laying the bedding layer?
- AInstalling a perimeter edge restraint system before any excavation.
- BExcavating to a minimum depth and compacting the subgrade to at least 95% Standard Proctor density.
- CApplying a weed barrier fabric directly over the native soil.
- DSpreading a 1-inch layer of uncompacted sand directly on the native soil.
Show answer & explanationAnswer & explanation
Correct answer: B. Excavating to a minimum depth and compacting the subgrade to at least 95% Standard Proctor density.
Compacting the subgrade (native soil) to at least 95% Standard Proctor density is the single most critical step for preventing differential settling in any paver installation, especially for high-traffic areas. A well-compacted subgrade provides a stable, uniform foundation that distributes loads evenly and prevents future settlement, which would lead to an uneven and failing walkway.
Why the other options are wrong
- A. Edge restraint is important for containing the pavers and bedding layer laterally, but it does not address the vertical stability and settlement of the underlying subgrade.
- C. Weed barrier fabric helps with weed control but does not contribute to structural stability or prevent settling.
- D. Uncompacted sand directly on native soil would lead to significant settling and instability under heavy pavers and traffic.
Paver Subgrade Compaction
The process of densifying the native soil beneath a paver system to achieve a specified density, crucial for long-term stability.
- Prevents differential settling.
- Provides a stable foundation for the base layers.
- Typically requires 95% Standard Proctor density.
Memory trick: A strong paver path needs a ROCK-SOLID earth foundation, like a skyscraper's base.