--- title: "Earthquake protection of load bearing masonry" subject: "Building Technology" chapter: 11 key: "semester_6/building_technology:eq-load-bearing-masonry" source: https://www.bctengineer.com/q/semester_6/building_technology/eq-load-bearing-masonry site: BCT Engineering --- # Earthquake protection of load bearing masonry Building Technology · Chapter 11: Earthquake protection & Retrofitting in building - Asked in: 2074 Bhadra, 8 marks - Video: [Constructing Low rise Confined Masonry Buildings: a Guide for Builders and Architects](https://www.youtube.com/watch?v=mGcp98ae5z4) — Earthquake Engineering Research Institute (EERI) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/building_technology/eq-load-bearing-masonry - Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-11 ## Question How earthquake protection can be achieved for a load bearing masonry building? What are the factors to be considered for improving building for seismic safety? ## Short answer Earthquake protection is achieved by a simple symmetrical plan, low height, good mortar (1:4–1:6), bricks ≥3.5 N/mm², small openings, and horizontal RC bands (plinth, lintel, roof) with vertical bars at corners and jambs. Factors for seismic safety include a rectangular plan with length:breadth ≤3, regular elevation, light roof, limited openings, cross-walls, uniform foundation, plinth band, seismic gap, and quality workmanship. ## Answer #### Principles for masonry - Use a simple, symmetrical plan and avoid long walls (keep the length between cross-walls to about 4-6 m). - Keep the building low (limit the number of storeys as per NBC 202 / IS 4326). - Use good mortar (cement-sand 1:4 to 1:6, not mud) and fill all joints; use bricks with a crushing strength of at least 3.5 N/mm^2 (class as per code). - Keep openings small and well placed (see below). #### Measures to make masonry earthquake resistant 1. **Horizontal bands:** RC plinth, lintel and roof bands tying all the walls together. 2. **Vertical reinforcement:** steel bars at corners, T-junctions and jambs of doors/windows, anchored in the foundation and the roof band. Typically one bar of 10 mm (single storey) to 12 mm (more storeys) at each corner. 3. **Openings:** total width of openings not more than 50% of the wall length in a single storey; piers between openings at least 340 mm wide; openings at least 600 mm from an inside corner (or as per the NBC 202 table). 4. **Cross walls and buttresses:** provide cross-walls within the spacing limits, and buttresses on long walls, to prevent out-of-plane failure. 5. **Good bonding at corners:** use toothing or stitching (and dowel bars) so that the walls do not separate. 6. **Light, well-anchored roof:** use light roofing and anchor trusses or rafters to the roof band; avoid heavy mud roofs and unanchored parapets, chimneys and gable ends. 7. **Strong foundation:** firm, uniform soil with a plinth band; avoid mixed foundations. 8. **Seismic gaps and separation:** for L or T plans. 9. **Quality control:** good workmanship and curing. ```text Wall elevation with bands and vertical bars |==================| roof band | | [] [] | | vertical bar at jamb |==================| lintel band | | |==================| plinth band ######## footing ``` #### Factors to be considered for seismic safety (configuration) - Simple rectangular plan with symmetrical walls; length : breadth not more than 3. - Regular elevation with continuous walls; low height and a light roof. - Limited, well-placed openings. - Cross-walls at regular spacing; good corner bonding. - Uniform foundation on firm soil, with a plinth band. - Seismic gap between different blocks. - Good-quality bricks, mortar and workmanship. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What is the purpose of RC plinth, lintel and roof bands in a masonry building? A. Increase the dead weight to resist overturning B. Tie all walls together so the building acts as a box C. Replace the need for a foundation D. Make the walls waterproof Answer: B. Continuous bands tie the walls so they act together and reduce out-of-plane bending. (Key point: Horizontal bands) 2. Where is vertical steel provided in an earthquake-resistant masonry building? A. At corners, T-junctions and jambs of doors/windows, anchored in foundation and roof band B. Only at the middle of long walls C. Only in the roof slab D. Randomly in the plinth Answer: A. Vertical bars at corners, junctions and jambs are anchored into the foundation and roof band. (Key point: Vertical reinforcement) 3. What plan is preferred for seismic safety of a masonry building? A. Long L-shaped plan with thin wings B. Any shape if walls are thick C. Simple rectangular, symmetric, length:breadth not more than 3 D. Narrow plan with length 6 times breadth Answer: C. Simple symmetric plans with aspect ratio up to 3 avoid torsion and large diaphragm stresses. (Key point: Plan configuration) 4. Which roof choice is best for seismic safety of a masonry building? A. Heavy mud roof for stability B. Light roof left unanchored on the walls C. Heavy RCC roof with no band D. Light roofing anchored to the roof band Answer: D. Earthquake force grows with mass, so use a light roof and anchor trusses/rafters to the roof band. (Key point: Roof and mass) ## Related in Building Technology - [Configuration factors for seismic safety](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aconfig-factors-seismic) — Building Technology, chapter 11, asked 2× - [Earthquake protection and resistant building principles](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aeq-protection-principles) — Building Technology, chapter 11, asked 3× - [Factors affecting foundation design, improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Afactors-design-improve-bc) — Building Technology, chapter 2 - [Methods of improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aimproving-bc) — Building Technology, chapter 2, asked 2× - [Soil exploration and improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Asoil-exploration-improving-bc-nepal) — Building Technology, chapter 2 - [Sub-soil exploration, improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Asubsoil-exploration-improve) — Building Technology, chapter 2 ## Related in other subjects - [Seismic base shear of a masonry building](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Abase-shear-two-storey-masonry-building) — Design of Timber and Masonry Structures, chapter 7 - [Improving seismic performance of masonry](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aseismic-performance-improvement) — Concrete Technology and Masonry Structure, chapter 9 - [Quantity method for load bearing brick building](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aquantity-method-load-bearing-brick) — Estimating and Costing, chapter 2 - [Load bearing building: excavation, brick, plaster](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Abuilding-g-load-bearing-23) — Estimating and Costing, chapter 6