IS 4326:1976 is the Indian Standard (BIS) for earthquake resistant design and construction of buildings: masonry buildings. This code provides prescriptive architectural and structural guidelines for the earthquake-resistant design and construction of masonry buildings. It focuses on limits for wall openings, mandatory provisions of horizontal seismic bands (plinth, lintel, roof), and vertical reinforcement at critical corners and junctions to ensure box-action during seismic events.
Provided guidelines for earthquake resistant design and construction of masonry buildings (superseded by modern codes).
Construction of earthquake-resistant masonry buildings. Bands, vertical reinforcement, opening rules.
| Reference | Value | Clause |
|---|---|---|
| Applicability — masonry building category A | Zone II–III, ≤ 3 storeys | Cl. 7.1 (Table 1) |
| Category B | Zone IV ≤ 3 storeys, Zone V ≤ 2 storeys | Cl. 7.1 (Table 1) |
| Plinth band — required for category | B, C, D, E | Cl. 8.4 (Table 4) |
| Lintel band — all openings | Mandatory all categories | Cl. 8.4.1 |
| Roof band — sloping/flat roof | Mandatory categories C–E | Cl. 8.4 (Table 4) |
| Gable band — sloping roof | Mandatory categories C–E | Cl. 8.4 |
| Band thickness — RCC | 75 mm minimum | Cl. 8.5.1 |
| Band reinforcement — minimum | 2 nos 8 mm Fe415 + 6 mm stirrups @ 150 mm | Cl. 8.5.1 (Table 5) |
| Vertical reinforcement — corner | 16 mm bars all corners + T-junctions | Cl. 8.6 (Table 6) |
| Vertical reinforcement — opening jambs | 12 mm minimum each side | Cl. 8.6 (Table 6) |
| Maximum opening width — wall length 3 m | 0.40 × wall length | Cl. 5.3 (Table 2) |
| Maximum opening width — wall length 5 m | 0.42 × wall length | Cl. 5.3 |
| Minimum pier between openings | 560 mm (Cat A–C), 600 mm (D), 750 mm (E) | Cl. 5.3 |
| Distance from corner to first opening | ≥ 450 mm | Cl. 5.3 |
| Wall thickness — minimum (load-bearing) | 200 mm (Zone II–III), 230 mm (Zone IV–V) | Cl. 7.4 |
| Building plan — preferred | rectangular, length ≤ 3 × width | Cl. 5.1 |
| Roof type preferred | RCC slab (rigid diaphragm) | Cl. 5.5 |
| Lintel-band continuity | continuous over all walls | Cl. 8.4.1 |
| Mortar — minimum grade for category B | 1:6 (cement:sand) | Cl. 6.2 (refers IS 1905) |
| Mortar — minimum grade for category C–E | 1:4 to 1:5 | Cl. 6.2 |
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Minimum Wall Thickness (Brick) | 230 mm (one brick length) | 150 mm (6 inches) for load-bearing or shear walls, with h/t ratios also governing. | TMS 402/602-22 |
| Minimum Mortar Type (Seismic Areas) | 1:6 Cement:Sand mix (min), 1:4 recommended for higher zones. | Type S or M mortar, defined by minimum compressive strength (e.g., 12.4 MPa for Type S) rather than mix ratio. | TMS 402/602-22 |
| Horizontal Lintel Band Reinforcement | Min. 2 bars of 8 mm diameter. | Calculated based on load, but prescriptive minimums exist. E.g., two 15M bars (similar to 16 mm dia) in NZS 4229. | NZS 4229:2013 |
| Vertical Reinforcement at Corners | Min. one 8 mm bar at each corner. | Min. one No. 4 bar (12.7 mm dia) at corners and ends of walls for special reinforced masonry shear walls. | TMS 402/602-22 |
| Max. Spacing of Horizontal Reinforcement | Not explicitly specified, provided as bands at lintel/roof levels. | Shall not exceed the lesser of wall height/3, wall length/3, or 1200 mm (48 inches). | TMS 402/602-22 |
| Minimum Pier Width | 600 mm for buildings up to two storeys. | 600 mm for concrete masonry (prescriptive). For engineered design, it must be sufficient to resist calculated forces. | NZS 4229:2013 |
| Total Length of Openings | Limited to 0.5x wall length (1-storey), 0.42x (2-storey), etc. | Less than 50% of the wall length (prescriptive). For engineered design, depends on shear capacity of remaining piers. | NZS 4229:2013 |