CSLB C-27 Landscaping ContractorHardscape and FeaturesEasy
A client wants a low-maintenance, permeable patio that allows rainwater to infiltrate the ground. Which type of bedding course material is most appropriate to lay directly beneath the permeable pavers to facilitate drainage and support the pavers?
- ACompacted decomposed granite
- BWashed concrete sand
- CCrushed limestone fines
- DOpen-graded aggregate (e.g., #8 or #9 stone)
Show answer & explanationAnswer & explanation
Correct answer: D. Open-graded aggregate (e.g., #8 or #9 stone)
For permeable paver systems, an open-graded aggregate, such as #8 or #9 crushed stone, is used as the bedding course. Its uniform size and lack of fines allow water to pass through freely, facilitating infiltration while providing a stable base for the pavers.
Why the other options are wrong
- A. Compacted decomposed granite has too many fines and would impede water infiltration, making it unsuitable for permeable applications.
- B. Washed concrete sand has fine particles that can clog the permeable system and impede drainage.
- C. Crushed limestone fines (screenings) are too fine and would not allow water to pass through effectively, defeating the purpose of a permeable system.
Permeable Paver Bedding Course
The bedding course for permeable pavers is a crucial layer that provides a level surface for the pavers and allows water to infiltrate efficiently. It must consist of an open-graded aggregate with very little to no fine material.
- Facilitates water infiltration into the sub-base.
- Must be open-graded to prevent clogging.
- Commonly #8 or #9 crushed stone.
Memory trick: Permeable means porous, so open-graded is glorious!