Patio Base: Grade 8 vs. Grade 9 Limestone—What's the Difference?

Contractors bid Grade 8 limestone; you were told to specify Grade 9. What's the diff? Why Grade 9?

Grade Numbers = State DOT Specs

Grading is governed by local/state DOT or road commission. Grade 8 and 9 are regional designations—not universal. Could be:

• Different top size (¾" vs 1").
• Different fines content (drainage vs. compaction).
• Different fracture requirements.

Who Told You Grade 9?

Ask them for the spec sheet. Then call your city/county engineering office or a local quarry—they'll translate.

More Important Than Grade: Drainage

• Slope patio 1–2% away from house.
• Install perimeter drain (NDS, 4" perforated + sock) at base of excavation.
• Daylight to pop-up emitter or swale.

Base grade matters less than water management. A Grade 8 base with great drainage outperforms Grade 9 in a bathtub.