Design Rules🏛 Structural — RCC

PCC Layer — Thickness Under Footing

Plain cement concrete blinding layer below RCC footings and rafts
See also📖 IS 456🔗 IS 456🔗 IS 1080🧮 RCC Design📒 Handbook Topic
75 to 100
mm
M10 (1:3:6) typical
NGLRCC FOOTING100mmPCC BLINDING LAYERM10 (1:3:6) · projects 75–150 mm beyond footing edge
Primary value75 to 100 mm (M10 (1:3:6) typical)
Applies toBelow isolated and combined footings · Below raft slabs · Below pile caps · Below ground floor flooring on grade
ExceptionsBelow raft on weak soil100–150 mm
Below ground floor floor slab75 mm
Heavy industrial flooring150–200 mm
Mix grade for PCCM7.5 or M10 (nominal mix 1:3:6)
Measured asCompacted thickness of plain cement concrete laid directly on prepared subgrade, projecting 75–150 mm beyond the footing edge on all sides to give a clean working platform.
SourceIS 456Clause 26.4.2.1, IS 1080
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Why this matters

PCC blinding is not a structural layer — it exists to give a clean, level base for placing reinforcement and to stop the soil from sucking water out of the structural concrete (which would compromise the RCC w/c ratio). 75 mm is the minimum that won't crack under foot traffic during steel-fixing; 100 mm is the safer default.

Typical practice

Standard practice in India is 100 mm PCC of M10 grade extending 75 mm beyond the footing edge. The PCC is part of the cover-control system — without it, the bottom 50 mm of cover specified for the RCC footing cannot be reliably maintained.

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