SIMAQ School · 5 min
Flexible pavement
A flexible pavement has four layers, top to bottom: asphalt surface (5–10 cm), base (10–30 cm), sub-base (10–30 cm) and subgrade (20–50 cm). Each one is compacted before the next goes on: the subgrade with a padfoot roller or the SQ60 PRO 2 rammer, base and sub-base with a smooth roller or the SQ15 PRO plate, and the asphalt hot with a double-drum smooth roller like the SQRDWB L34.
Learn the layers and terms to talk shop with your clients — especially about compaction.
Asphalt surface · 5–10 cm
The wearing course you see and traffic rolls on. Compacted hot, no voids.
Compacted with
Smooth / pneumatic roller (tandem)
Each layer is compacted before the next goes on. If a lower layer is loose, the whole pavement fails — that's why subgrade and base compaction matter most. Speaking in these terms positions you as a supplier who understands the job.
Which machine compacts each layer
A cohesive subgrade needs impact; granular base and sub-base need vibration; the asphalt, a smooth roller while hot.
Not sure which compactor fits your soil? Soil compaction lesson
Watch it
Short clips of the gear
FAQ
What people ask most
What are the layers of a flexible pavement and how is each one compacted?
Top to bottom: asphalt surface (5–10 cm), base (10–30 cm), sub-base (10–30 cm) and subgrade (20–50 cm). The subgrade is compacted with a padfoot roller or rammer, base and sub-base with a smooth roller or plate compactor, and the asphalt hot with a tandem smooth roller.
What is the subgrade?
It's the prepared, compacted natural ground: the foundation of the whole pavement. If it's clay, it's compacted by impact, with a padfoot roller like the SQRPTRC L202 or the SQ60 PRO 2 rammer.
What do the base and sub-base do?
The base is the granular layer that spreads traffic load downward. The sub-base is the transition between base and ground: it drains water and adds support.
What do you compact asphalt with?
Hot, with a double-drum smooth roller like the SQRDWB L34, which has front and rear water spray so the asphalt won't stick. For patching and small areas, the SQ15 PRO plate has a water tank and an asphalt sprinkler kit.
What happens if a lower layer is poorly compacted?
The whole pavement fails, even if the surface looks fine at first. That's why each layer is compacted before the next goes on, and subgrade and base matter most.
Get a quote without leaving
Want to work it out with an advisor?
Topic: Compaction for pavement
Keep learning
Ready for a quote?
Tell us about the job and we'll build the package. A rep replies during business hours.