IS 2118:1980 is the Indian Standard (BIS) for construction of jack-arch type of bult-up floor or roof. This code outlines the materials, design guidelines, and construction procedures for jack-arch type built-up floors and roofs. It details the specifications for rise-to-span ratios, steel joist placement, tie rod requirements, and brick-laying techniques to ensure structural stability.
Code of Practice for Construction of Jack-Arch Type of Bult-up Floor or Roof
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Arch Rise to Span Ratio | Shall be 1/12 of the span. | Typically a range from 1/10 to 1/12 of the span is used; not a fixed rule. | General UK Historical Practice |
| Maximum Span of Arch (between joists) | Shall not generally exceed 1.2 m. | Typically 0.9 m to 1.5 m (3 to 5 feet). | General UK/US Historical Practice |
| Spacing of Tie Rods | 1.8 m to 2.4 m. | Typically 1.8 m to 2.5 m, but modern analysis would require spacing to be calculated based on arch thrust. | EN 1996-1-1 (Principle of calculation) |
| Minimum Arch Thickness (at crown) | Not less than 10 cm. | Typically one half-brick length, approx. 102.5 mm - 115 mm. | General Masonry Practice |
| Minimum Concrete Topping Thickness (over crown) | Not less than 5 cm. | Minimum 50-75 mm, especially for distributing point loads. | Historic England Technical Guidance |
| Joist Bearing on Walls | Not less than 15 cm. | Minimum 100 mm to 150 mm (4 to 6 inches) is typical. | AISC / General Steel Design Practice |