For a masonry building in seismic Zone III, as per IS 4326, the horizontal bands are mandatory at
- APlinth level, lintel level and roof levelCorrect
- BOnly at roof level
- COnly at plinth level
- DNo bands required
Solution
Concept
Mandatory horizontal bands for masonry in Zone III
Formula
IS 4326: Clause 8.4 & Table 4 - Horizontal Bands
Step-by-step solution
1. Masonry buildings in seismic regions must function as a coherent three-dimensional box under lateral forces. 2. IS 4326 Table 4 details mandatory provisions for seismic bands in Zone III. 3. Horizontal bands are mandated at the plinth level (especially on softer soils), lintel level (across all openings), and roof level (to transfer diaphragm action). 4. Therefore, horizontal bands are required at plinth level, lintel level, and roof level. Answer: A
Explanation
As per IS 4326 Table 4, in Seismic Zone III, horizontal reinforced concrete bands must be provided at plinth level (in soft soils), lintel level (mandatory in all buildings), and roof level (for flat roofs or roofs with trusses) to tie walls together into a box unit.
Why the other options are wrong
B) Providing bands only at roof level allows severe cracking around openings. C) Providing bands only at plinth level fails to tie walls at top levels. D) Zone III is a moderate seismic zone where horizontal bands are legally mandatory.
Shortcut
Zone III masonry = Horizontal bands at plinth, lintel, and roof levels.
Common mistake
Providing a band only at the roof level, leaving window and wall heights unreinforced against out-of-plane bending.
Correct answer: A) Plinth level, lintel level and roof level