Rebar Spacing (Min/Max)

Rebar spacing is the distance between adjacent reinforcement bars in concrete members. Per IS 456:2000 Cl. 26.5.1: minimum spacing between bars = greater of: (a) bar diameter, (b) maximum aggregate size + 5 mm, or (c) 25 mm. Typical Indian concrete with 20 mm aggregate + 16 mm rebar: minimum spacing = max(16, 25, 25) = 25 mm. Maximum spacing — for shear reinforcement: ≤ 0.75d or 300 mm; for longitudinal column bars: ≤ 200 mm c/c.

Spacing affects: (a) Concrete compaction — too-tight spacing prevents aggregate flow during pour, causing honeycombing. (b) Bond development — adequate spacing ensures concrete-to-steel bond. (c) Crack control — uniform spacing distributes cracks. (d) Workmanship — too-tight spacing makes site placement difficult. For typical Indian residential beams: bottom bars at 50-100 mm spacing; top bars at 80-120 mm; stirrups at 150-200 mm c/c. For columns: corner bars at 200-250 mm; intermediate bars at 150-200 mm; stirrups at 150-300 mm c/c.

The most-overlooked aspect: rebar spacing relaxation in middle of members. Workers often pull stirrups apart in the middle of beams or columns to ease placement of main bars; this reduces shear capacity. Site QC must verify stirrup spacing pre-pour against BBS.