Section R506 — CONCRETE FLOORS (ON GROUND)
2025 California Residential Code (Title 24, Part 2.5) · 2025 edition · ingested 2026-07-07 · California
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R506.1 General. ¶
R506.1 General. Concrete slab-on-ground floors shall be designed and constructed in accordance with the provisions of this section or ACI 332. Such floors shall be not less than 3 [1] / 2 inches (89 mm) thick (for expansive soils, see Section R403.1.8). The specified compressive strength of concrete shall be as set forth in Section R402.2.
R506.2 Post-tensioned slab-on-ground floors. ¶
R506.2 Post-tensioned slab-on-ground floors. Post-tensioned concrete slabs-on-ground floors placed on expansive or stable soils shall be designed in accordance with PTI DC10.5.
R506.3 Site preparation. ¶
R506.3 Site preparation. The area within the foundation walls shall have all vegetation, topsoil and foreign material removed. R506.3.1 Fill. Fill material shall be free of vegetation and foreign material. The fill shall be compacted to ensure uniform support of the slab, and except where approved, the fill depths shall not exceed 24 inches (610 mm) for clean sand or gravel and 8 inches (203 mm) for earth. R506.3.2 Base. A 4-inch-thick (102 mm) base course consisting of clean graded sand, gravel, crushed stone, crushed concrete or crushed blast-furnace slag passing a 2-inch (51 mm) sieve…