Earthquake-Safe House in India: Seismic Zones, IS 1893 and IS 13920

India's earthquake zones come from IS 1893 (Part 1):2016, which divides the country into Zones II, III, IV and V, with Zone V the most severe. BIS withdrew the 2025 revision of the map in March 2026, so the 2016 zones still apply and there is no Zone VI. In Zones III, IV and V, every RCC house, single storey or not, must follow the ductile detailing of IS 13920:2016, and a structural drawing is how that detailing reaches the site.

Seismic zones in plain words

IS 1893 gives each zone a zone factor, used by engineers to work out earthquake forces, and links each zone to an intensity on the MSK scale:

• Zone II: zone factor 0.10, intensity VI or less
• Zone III: zone factor 0.16, intensity VII
• Zone IV: zone factor 0.24, intensity VIII
• Zone V: zone factor 0.36, intensity IX and above

Some examples from our city guides: Lucknow is in Zone III, Delhi and Patna are in Zone IV, and Guwahati is in Zone V. Gorakhpur, where our head office is, is listed in Zone IV in Annex E of IS 1893.

About "Zone VI": a 2025 revision of IS 1893 added a Zone VI for the Himalayan belt. BIS withdrew it by a notification dated 3 March 2026, as reported at the time, so IS 1893 (Part 1):2016 is the code in force. A page that puts your town in Zone VI is out of date.

What "earthquake-safe" means

IS 1893 says plainly that structures designed to it are expected to be damaged in strong shaking. IS 13920 aims for members strong and ductile enough "to resist severe earthquake shaking without collapse." So the goal is a house that may crack in a big earthquake but does not fall on the family inside. That is why the details matter more than the thickness of the concrete.

RCC houses: what IS 13920 asks for

IS 13920:2016 applies to all RC structures in Zones III, IV and V, and is optional in Zone II. A few of its rules, in plain words:

• Concrete: at least M20, and M25 for buildings taller than 15 m in Zones III to V.
• Columns: the smaller side at least 300 mm, or 20 times the diameter of the largest beam bar meeting the column, whichever is more. The 230 mm (9 inch) columns common in small houses do not meet this.
• Strong columns, weaker beams: at each joint, the columns together must be at least 1.4 times as strong as the beams, so beams yield before columns do.
• Hooks: column links must be closed, with 135° hooks extending 6 times the bar diameter (not less than 65 mm) into the core. A 90° hook can open in an earthquake.
• Closer links near joints: extra confining links over a length of at least 450 mm (more for bigger members and longer spans) on each side of every beam-column joint.

These rules mean more steel than a thumb rule. Estimating guides disagree on how much more for Zones IV and V (one says 10–15%, another 15–25%), which is why our materials guide gives it only as a rough range. The structural drawing for your house gives the real figure.

Load-bearing (masonry) houses: IS 4326

Many single and double storey houses, especially in villages and small towns, are built with load-bearing brick walls instead of an RCC frame. IS 4326:2013 sets out how to strengthen them. Depending on the zone and the building, it asks for:

• a lintel band: a continuous reinforced concrete band at lintel level on all load-bearing walls
• a roof band just below the roof or floor, where needed
• a plinth band where needed
• vertical steel bars at corners and wall junctions, and at the sides of openings, in the higher categories

The bands tie the walls together so the house moves as one box instead of the walls falling outward.

The ground floor with parking: a soft storey

Many houses leave the ground floor open for parking, with walls only on the floors above. IS 1893 calls a storey whose stiffness is less than the storey above a "soft storey". In earthquakes, buildings often fail at such a floor. It can be designed safely, but only if the structural engineer knows about it and designs for it, which is one more reason not to build from a floor plan alone.

Why a structural drawing matters

A contractor building from experience will usually put up a house that stands under its own weight. Earthquake loads are different, and the rules above live in the structural drawings:

• footing sizes from your soil test
• a column schedule with every bar and link
• beam and slab drawings with the joint details
• a bar bending schedule, so the steel is cut and bent as designed

Our structural design includes earthquake-resistant detailing for the seismic zone of your city, and our house design packages include structural drawings with the floor plans. See what each package covers on the packages page.

What to check on site

• Column links closed with 135° hooks, not bent at 90°.
• Links closer together near every joint, as drawn.
• Cover blocks under and around the steel before every pour.
• Column sizes and bar counts exactly as in the column schedule.
• No column or beam cut later for pipes or wiring.

Seedhi baat: bhookamp se bachav mehenge cement se nahi, sahi sariya ki bandhai (detailing) se hota hai.

Common questions

Is my city in Zone VI?

No. The 2025 map with Zone VI was withdrawn in March 2026. The zones of IS 1893 (Part 1):2016, II to V, apply.

Does a single-storey RCC house need earthquake detailing?

In Zones III, IV and V, yes. IS 13920 applies to the RC structure there whatever its height. In Zone II it is optional but still good practice.

Will an earthquake-resistant house not crack at all?

It may crack in strong shaking. The aim of the codes is that it does not collapse.

How much extra does earthquake detailing cost?

It is mostly extra steel and labour for the detailing. Estimating guides disagree on the amount, so ask for the structural drawing and the bar bending schedule for your own house.

Sources

• BIS, IS 1893 (Part 1):2016, Criteria for Earthquake Resistant Design of Structures, Table 3 and Annex E — https://archive.org/details/gov.in.is.1893.1.2016
• BIS, IS 13920:2016, Ductile Design and Detailing of Reinforced Concrete Structures Subjected to Seismic Forces, clauses 1.1, 1.1.1, 5.2, 7.1.1, 7.2.1, 7.4.1 and 8.1 — https://archive.org/details/gov.in.is.13920.2016
• BIS, IS 4326:2013, Earthquake Resistant Design and Construction of Buildings, clause 8.4 and Table 5 — https://archive.org/details/gov.in.is.4326.2013
• Withdrawal of the 2025 map: Vision IAS summary of The Economic Times, 7 March 2026 — https://visionias.in/current-affairs/upsc-daily-news-summary/article/2026-03-07/the-economic-times/environment/bis-revokes-new-seismic-map-with-high-risk-zone-vi
• Extra steel in Zones IV and V: InfraLens, cement, sand and steel for a 1,000 sq ft house — https://infralens.in/knowledge/cement-sand-steel-for-1000-sqft-house

Send your plot size and city on WhatsApp, or use the quote form, and we will tell you which seismic zone your structural drawings will be designed for.