Handbook›Concrete Cover Requirements

Concrete Cover Requirements

IS 456:2000 · Table 16 — Nominal Cover to Meet Durability Requirements, Table 16A — Cover for Fire Resistance

Minimum nominal concrete cover protects reinforcement from corrosion and fire. Cover depends on exposure condition (Table 16) and required fire resistance (Table 16A). Always use the larger of the two.

IS 456 →

Quick Lookup — By Exposure

30mmMin M25

Sheltered from severe rain, indoor RCC

Nominal Cover for Durability (Table 16 of IS 456)

Exposure	Cover (mm)	Min Grade	Examples
Mild	20	M20	Concrete fully protected, dry interiors
Moderate	30	M25	Sheltered from severe rain, indoor RCC
Severe	45	M30	Exposed to rain, alternate wet/dry, coastal (>500m from sea)
Very Severe	50	M35	Coastal environment, aggressive soil/ground water, industrial chemicals
Extreme	75	M40	Tidal zone, direct sea water splash, highly aggressive chemicals

Quick Reference by Member Type

Member	Cover	Bar Ref	Exposure
RCC Slab (interior residential)	20	Main bar	Mild
RCC Slab (exterior/balcony)	30	Main bar	Moderate
RCC Beam (interior)	25	Stirrup face	Mild
RCC Beam (exterior)	30	Stirrup face	Moderate
RCC Column (interior)	40	Tie face	Mild/Moderate
RCC Column (exterior)	40	Tie face	Moderate
Footing	50	Bottom bar	In contact with soil
Retaining Wall (earth face)	50	Main bar	Severe
Water Tank (inside face)	45	Main bar	Severe
Pile / Pile Cap	60	Main bar	In contact with soil
Raft Foundation	75	Bottom bar	Against ground
RCC Staircase	25	Main bar	Mild

Cover for Fire Resistance (Table 16A of IS 456)

Fire rating in hours — use the larger of durability cover and fire cover

Member	0.5h	1h	1.5h	2h	3h	4h
Slab (simply supported)	20	20	25	35	45	55
Slab (continuous)	20	20	20	25	35	45
Beam (simply supported)	20	20	20	40	60	70
Beam (continuous)	20	20	20	30	40	50
Column	40	40	40	40	40	40
Wall (load-bearing)	20	20	25	25	25	25

Practical Notes

• Nominal cover = clear cover to nearest surface of the outermost reinforcement (including stirrups)

• Cover to main bar ≥ bar diameter (Clause 26.4.1)

• For bundled bars, cover ≥ equivalent diameter of the bundle

• Cover blocks (spacers): use PCC cover blocks, NOT stone/brick pieces

• Maximum cover should not exceed 75mm unless designed for fire resistance

• In aggressive environments (coastal, industrial), consider additional 10mm beyond code minimum

• For precast elements, cover may be reduced by 5mm per IS 456 Clause 26.4.2

• Tolerance on cover: +10mm, −0mm (cover must never be less than specified)

• Always check both durability and fire requirements — use the LARGER value

← Previous

Development Length & Lap Length

Dead Loads of Building Components

Generated by InfraLens · infralens.in