Most homeowners never see the structure of their home. Once the plaster, putty, paint and false ceiling go on, columns look like wall corners, beams look like bulkheads, and the slab is just the ceiling. That invisibility causes real problems during interior work. Walls are knocked down to make an open kitchen without anyone checking whether they carry load; holes are cored through beams for AC pipes and exhaust ducts; conduits are chased deep into columns; heavy stone cladding, terrace gardens and water tanks are added to slabs designed for a family's furniture. Most of the time nothing visible happens immediately, which is exactly why the habit continues.
This article explains, in plain language, what columns, beams and slabs do, how load travels through a building, what typical sizes look like in Indian houses and apartments, what the main Indian codes require in broad terms, and which warning signs need attention. It is written to help homeowners ask better questions — not to replace engineering. The guidance is deliberately conservative: any change to a structural element, and any significant new load, needs a licensed structural engineer, and in apartments the society and often the original developer's engineer as well.
From stone lintels to reinforced concrete: a short history
For most of history, Indian buildings were load-bearing: thick walls of stone, brick, mud or rubble carried the roof, and openings were spanned with stone lintels, timber beams or arches. Roofs were timber rafters with tiles, flat terraces of timber joists and lime concrete, or brick vaults and domes. In the late nineteenth and early twentieth centuries, two hybrid roofs became widespread in Indian towns: the jack arch roof, with shallow brick arches spanning between steel I-section joists, and the Madras terrace roof, with brick laid on edge over timber joists and finished with lime concrete. Many old buildings still standing in Surat, Ahmedabad, Mumbai and Chennai use these systems, which have their own rules for safe alteration.
Reinforced concrete — concrete with steel bars embedded to carry tension — was developed in Europe in the second half of the nineteenth century and spread worldwide in the twentieth. In India it became the default for multi-storey buildings after independence, and today almost every new house and apartment is an RCC frame of columns, beams and slabs, with brick, block or AAC infill walls. The Bureau of Indian Standards' IS 456 (Plain and Reinforced Concrete — Code of Practice), whose current edition is IS 456:2000, governs its design, together with IS 875 for loads, IS 1893 for earthquake forces and IS 13920 for ductile detailing in seismic regions. Part 6 of the National Building Code of India 2016 brings these together for structural design.
How load travels through a building
A building carries two broad kinds of load. Dead load is the permanent weight of the structure and finishes: concrete, walls, plaster, flooring, waterproofing, built-in furniture. Live or imposed load is the changing weight of people, furniture, stored goods and water; IS 875 Part 2 sets design values, for example 2.0 kN/m² for typical residential floors. On top of these come wind loads (IS 875 Part 3) and earthquake forces (IS 1893). The structure's job is to collect all of this and deliver it safely to the ground along a continuous path.
In a typical RCC frame, the slab spans between beams and passes its load to them; the beams span between columns and pass their load to them; the columns carry the accumulated load of every floor above down to the footings; and the footings spread it over a large enough area of soil that the ground does not settle unevenly. Every link in that chain was sized for a specific load in a specific position. Cutting a beam, removing a column, coring a large hole in a slab or adding a heavy new load somewhere unexpected changes the chain. Sometimes the structure has enough reserve to cope; sometimes it does not; and only calculation by an engineer with the drawings can say which.
Framed, load-bearing and shear-wall buildings
The first question before any alteration is what kind of structure the building is. In an RCC framed building, columns and beams carry the load and most walls are infill — they keep out weather and divide rooms, but carry only their own weight. In a load-bearing building, the walls themselves carry the floors and roof, so removing or enlarging an opening in them removes support. In many modern high-rise apartments, some walls are RCC shear walls: concrete walls, often 150–300 mm thick and plastered to look like any other wall, that resist wind and earthquake forces and frequently carry gravity load too. They cannot be removed or opened up. From inside a finished flat, these three can look identical.
| Building type | What carries the load | Where common | Can a wall be removed? |
|---|---|---|---|
| RCC frame with infill walls | Columns, beams, slabs | Most houses and low- to mid-rise apartments since the 1970s | Infill walls often can, but only after an engineer confirms it — some carry loads or bracing |
| Load-bearing masonry | Brick or stone walls | Older houses, chawls, many pre-1970s buildings | Generally no; openings need engineer-designed lintels or frames |
| RCC shear-wall (Mivan / aluminium formwork) towers | RCC walls and slabs | Many high-rise apartments since the 2010s | No — most internal walls may be structural |
| Jack arch or Madras terrace roofs on masonry | Masonry walls + steel or timber joists | Old city houses in Gujarat, Mumbai, Chennai | No; alterations need a heritage-aware engineer |
| Steel frame | Steel columns and beams | Commercial, industrial, some modern homes | Only with engineer's approval; fire protection matters |
| Mixed or extended buildings | Combination — often undocumented | Homes extended floor by floor over decades | Treat as unknown until investigated |
Columns: the most important element in the house
Columns collect load from every floor above and deliver it to the foundation, so a column failure affects everything it supports. A column is concrete in compression, with vertical steel bars (longitudinal reinforcement) that add strength and resist bending, held in place by closed ties or links at regular spacing. The ties stop the vertical bars buckling outward and confine the concrete core — which, in an earthquake, is what keeps a column standing after the outer concrete cracks. That is why IS 13920 requires closely spaced ties near beam–column joints and 135-degree hooks that anchor into the core rather than opening up.
Older Indian houses commonly have 230 × 230 mm or 230 × 300 mm columns, sized to fit inside a nine-inch brick wall. Modern design for buildings that must follow ductile detailing is more demanding: the 2016 revision of IS 13920 generally requires a minimum column dimension of 300 mm, and many engineers now specify 300 × 450 mm, 300 × 600 mm or larger for ground-floor columns of a two- or three-storey house, depending on loads, spans, soil and seismic zone. Surat, for example, lies in seismic zone III under IS 1893. The exact size and reinforcement must come from the engineer's design, never from a rule of thumb or a neighbour's house.
Beams: why holes and cuts are dangerous
A beam carries load sideways to the columns by bending. In a simply supported span, the bottom of the beam is stretched (in tension) near mid-span and the top is squeezed; in a continuous beam over several columns, the top is in tension over the supports. Concrete is weak in tension, so steel bars are placed where the tension is — at the bottom near mid-span and at the top near supports. Near the supports, the beam also carries high shear forces, which the vertical stirrups resist; IS 13920 requires stirrups at closer spacing over a length of twice the beam depth from each column face in seismic detailing. The practical result is that almost every part of a beam is doing something important.
Typical beams in Indian houses are 230 mm wide (to match the wall) and 300–600 mm deep, depending on span and load; for very early estimates engineers sometimes start with a depth of about one-tenth to one-fifteenth of the span, but final sizes come from calculation. Interior work commonly wants to put holes through beams — for AC refrigerant pipes, drain lines, exhaust ducts and conduits. A hole near a column cuts through the zone of highest shear and densest stirrups; a hole near the top or bottom cuts the main bars; a core cutter does not know where the bars are. Where an opening is unavoidable, the engineer may in some cases allow a small sleeve at a specific position — often near mid-depth and away from supports — with added reinforcement; that decision belongs to the engineer, preferably before the beam is cast so sleeves are built in.
Slabs: thin, wide and easy to overload
The slab is the floor of one level and the ceiling of the one below. In Indian homes, solid RCC slabs are typically 100–150 mm thick, with 125–150 mm common for rooms of ordinary span; longer spans, heavier loads and flat-slab or post-tensioned systems use thicker or different sections. A slab supported on all four sides with a long side less than about twice the short side spans in both directions (a two-way slab); a long, narrow slab, with a ratio of more than about two, spans mainly across the short direction (a one-way slab). Cantilever slabs — balconies, chajjas and projections without a support at the outer edge — are the most sensitive of all: their main steel is at the top, near the surface that floor tilers, waterproofers and plumbers cut into.
Slabs are where homeowners most often add load without realising it. A second layer of flooring laid over the old one adds the weight of the new tiles and the bedding mortar; a terrace garden with 450 mm of wet soil can weigh several times the slab's design live load; a 1000-litre water tank weighs about a tonne when full; a large aquarium, a stone bathtub, a heavy safe or a new brick wall built directly on a slab where none was designed all concentrate load in one place. None of these is automatically dangerous, but each needs an engineer's check against the original design, and some need beams, spreaders or relocation.
| Element | Typical in Indian homes | What it does | Never do without an engineer |
|---|---|---|---|
| Column | 230 × 300 (older) to 300 × 450 / 300 × 600 mm (newer, seismic detailing) | Carries every floor above to the foundation | Remove, cut, chase, notch, expose bars |
| Beam | 230 mm wide × 300–600 mm deep | Carries slab and walls to columns by bending | Core holes, cut, chase, remove, hang heavy loads |
| Solid slab | 100–150 mm (125–150 common) | Floor and ceiling; carries loads to beams | Large cut-outs, cores, heavy new loads, new walls on top |
| Cantilever slab (balcony, chajja) | 125–150 mm at root, steel at top | Projects beyond support | Cut grooves in top, add walls or tanks at tip, enclose with masonry |
| Shear wall (high-rise) | 150–300 mm RCC | Resists wind and earthquake; often carries load | Remove, open up, core large holes |
| Load-bearing wall | 230 mm and thicker masonry | Carries floors and roof | Remove, enlarge openings |
| Footing / foundation | Depth often 1200–2000 mm, soil-dependent | Spreads load into soil | Excavate beside it, add floors above |
Concrete, steel and cover: what IS 456 asks for
Durability is as important as strength. IS 456:2000 links the minimum concrete grade and the minimum clear cover over steel to the exposure condition of the element. For reinforced concrete, it sets M20 as the minimum grade for mild exposure, M25 for moderate, and M30 for severe, with higher grades for very severe and extreme conditions such as sea-water spray and tidal zones. Coastal cities like Surat, Mumbai and Chennai and sites near industrial pollution often warrant moderate-to-severe assumptions for exposed elements. Steel bars are typically high-strength deformed bars to IS 1786, commonly Fe 500 or the more ductile Fe 500D preferred in seismic design.
| Exposure (IS 456) | Typical situation | Minimum RCC grade | Nominal cover (general) | Notes |
|---|---|---|---|---|
| Mild | Concrete protected from weather, except coastal areas | M20 | 20 mm | Interior slabs and beams in dry, inland locations |
| Moderate | Sheltered from heavy rain; exposed to condensation or buried in non-aggressive soil | M25 | 30 mm | Many residential elements; coastal sheltered concrete |
| Severe | Exposed to severe rain, alternate wetting and drying, or coastal environment | M30 | 45 mm | Exposed beams, balconies and columns in coastal cities |
| Very severe | Exposed to sea-water spray, aggressive sub-soil | M35 | 50 mm | Seafront buildings, aggressive ground |
| Extreme | Tidal zone, direct contact with aggressive chemicals | M40 | 75 mm | Marine structures |
| Columns (any exposure) | Longitudinal bars | As above | ≥ 40 mm | IS 456 minimum for column longitudinal bars |
| Footings | In contact with soil | As above | ≥ 50 mm | IS 456 minimum for footings |
Two site practices matter as much as the numbers on drawings. Curing keeps concrete moist so it gains strength and resists cracking: IS 456 calls for at least 7 days for ordinary Portland cement concrete and at least 10 days where mineral admixtures or blended cements are used, or in hot, dry weather. Formwork and props must stay in place long enough for the concrete to carry its own weight and construction loads; IS 456 gives indicative minimum striking times for ordinary Portland cement concrete, which the engineer may adjust for the cement type, temperature and loads.
| Formwork (IS 456, OPC, indicative minimums) | Minimum period before removal |
|---|---|
| Vertical faces of walls, columns and beams | 16–24 hours |
| Slab soffits (props left under) | 3 days |
| Beam soffits (props left under) | 7 days |
| Props to slabs spanning up to 4.5 m | 7 days |
| Props to slabs spanning over 4.5 m | 14 days |
| Props to beams and arches spanning up to 6 m | 14 days |
| Props to beams and arches spanning over 6 m | 21 days |
Warning signs: cracks and distress worth calling an engineer about
Most cracks in Indian homes are not structural. Fine hairline cracks in plaster and putty, cracks along the joint between a concrete column or beam and a brick wall, and cracks at the top of walls under a terrace slab are commonly caused by shrinkage, thermal movement and the different behaviour of concrete and masonry. This site's wall cracks guide covers these in detail. Some patterns, however, need a structural engineer's inspection promptly, and the table lists the most common. When in doubt, photograph the crack with a scale, mark its ends and date with a pencil, and ask an engineer to look.
| Sign | What it may indicate | Urgency | Action |
|---|---|---|---|
| Diagonal cracks from corners of doors and windows, widening over time | Differential settlement or overstress | High | Structural engineer inspection; monitor width |
| Cracks in a beam near a column, or vertical cracks at mid-span bottom | Shear or bending distress | High | Engineer; do not load or cut further |
| Horizontal or crushing cracks in a column, bulging | Overload or deterioration of a primary element | Very high | Engineer immediately; reduce loads; consider propping as advised |
| Rust stains, spalled concrete, exposed corroded bars | Reinforcement corrosion — common in coastal cities | Medium to high | Engineer-led repair: remove loose concrete, treat steel, repair mortar |
| Sagging slab or balcony tip, doors that newly jam | Excess deflection or support movement | High | Engineer; keep people and loads off a sagging cantilever |
| Hairline cracks along column–wall or beam–wall joints | Shrinkage and thermal movement between materials | Low | Fill with flexible filler and mesh at repainting |
| Map cracks in plaster, fine and random | Plaster shrinkage | Low | Cosmetic repair |
Older buildings deserve particular care. Some municipal corporations require periodic structural audits of buildings beyond a certain age, and IS 15988 gives guidelines for seismic evaluation and strengthening of existing RC buildings. Repairs such as jacketing columns with additional concrete and steel, wrapping elements in fibre-reinforced polymer, or adding new frames are engineering interventions, designed and supervised by qualified structural engineers and carried out by specialist contractors.
Working with a structural engineer
For a new house, the structural engineer designs the foundations, columns, beams and slabs, issues structural drawings and bar-bending schedules, and should inspect the reinforcement at key stages before concrete is poured: footings, columns at each floor, and each slab with its beams. For a renovation, the engineer's role is to confirm what the structure is, check whether a proposed change or new load is acceptable, and design any strengthening needed. This site's planning guides note that a structural engineer's visit and written confirmation for a specific question typically costs about ₹3,000–15,000 depending on city and scope (indicative October 2026), a small fraction of a renovation budget and of the ₹1,800–3,800 per sq ft that new construction costs in tier-2 Gujarat cities.
| Situation | Engineer needed? | What to ask for |
|---|---|---|
| Removing or opening any wall in an apartment | Yes | Written confirmation that the wall is non-structural; society approval |
| Holes or sleeves in beams, slabs or shear walls | Yes | Marked positions and sizes, any added reinforcement, method (cast-in or approved coring) |
| Adding a floor, room, mezzanine or terrace structure | Yes — plus building permission | Check of columns, footings and seismic design |
| Terrace garden, water tank, pool, heavy safe, aquarium | Yes | Load check and position of supports or spreaders |
| Enclosing a balcony with masonry | Yes — and permissions | Cantilever load check; lighter alternatives |
| Heavy stone cladding or jaali on upper floors | Yes | Fixing detail into slab or beam, not infill |
| New house construction | Yes, from the start | Drawings, bar-bending schedule, stage inspections |
| Hairline plaster cracks only | Usually not | Monitor; call an engineer if they widen or follow the patterns above |
Where structural practice is heading
Structural engineering in Indian housing is moving in a clear direction: stronger, more durable and more earthquake-aware. Higher concrete grades and more ductile steels are becoming routine; ductile detailing to IS 13920 is more widely applied; aluminium-formwork shear-wall construction has changed how high-rise apartments are built, and with it the rules for what residents may alter. Post-tensioned slabs allow longer column-free spans in commercial and premium residential projects, with strict limits on coring. Precast and prefabricated elements, structural health monitoring with sensors in large buildings, and better retrofitting methods for older stock are spreading. For homeowners, the change that matters most is cultural: treating structural drawings as documents to keep, and the structural engineer as a professional to consult before interior work, not after a crack appears.
Rules for homeowners and interior contractors
- Treat every column, beam, slab, shear wall and load-bearing wall as untouchable without a licensed structural engineer's written approval.
- Ask for and keep the approved structural drawings; in apartments, get them from the society or developer.
- Never core, chase or notch a beam or column; route AC pipes, drains and ducts through walls, bulkheads or engineer-approved sleeves.
- Never assume a wall is non-structural because it is thin or sounds hollow — check, especially in high-rise shear-wall buildings.
- Get a load check before adding terrace gardens, water tanks, heavy stone, aquariums, safes, mezzanines or new walls on slabs.
- Never cut into the top of a cantilever balcony or chajja, or load its tip with masonry or planters.
- Insist on adequate cover, curing and prop periods during construction, as the engineer specifies under IS 456.
- Photograph and monitor any crack that follows the warning patterns, and call an engineer promptly.
- Use a licensed structural engineer and, where needed, building permission — never a contractor's opinion — for structural decisions.
Frequently asked questions
Can I remove a wall in my flat?
Only after a licensed structural engineer has confirmed in writing that the wall is non-structural, and after the society's approval as its bye-laws require. In RCC framed buildings many internal walls are infill, but in shear-wall towers most internal walls may be structural, and in older load-bearing buildings the walls carry the floors. Never decide from the wall's thickness or sound.
Can I drill a hole in a beam for AC pipes?
Not without a structural engineer's approval. Holes near columns or near the top and bottom of a beam cut through the most important steel and shear zones. Route pipes through walls, under the beam in a bulkhead, or through a sleeve whose size and position the engineer approves — ideally cast in during construction.
What is the minimum column size for a house in India?
There is no single answer; the engineer sizes columns for the loads, spans, soil and seismic zone. Older houses commonly have 230 × 230 or 230 × 300 mm columns, but the 2016 revision of IS 13920 generally requires a minimum dimension of 300 mm where ductile detailing applies, and 300 × 450 mm or larger is now common for ground-floor columns of two- or three-storey houses.
How thick should a house slab be?
Typically 100–150 mm, with 125–150 mm common for ordinary residential spans. Longer spans, heavier loads and cantilevers may need more, and flat or post-tensioned slabs follow their own design. The structural engineer fixes the thickness and reinforcement.
How can I tell if a crack is structural?
Fine random cracks in plaster and straight cracks along column–wall joints are usually not structural. Diagonal cracks from window and door corners that widen, cracks in beams near columns, horizontal or crushing cracks in columns, rust stains with spalling, and sagging slabs need a structural engineer's inspection. If unsure, mark and date the crack ends and ask an engineer.
Sources & standards
- Bureau of Indian Standards — IS 456:2000 (Plain and Reinforced Concrete — Code of Practice): exposure, grades, cover, curing and formwork striking
- Bureau of Indian Standards — IS 875 Parts 1–3 (Design loads: dead, imposed and wind); IS 1893 (Part 1):2016 (Criteria for earthquake resistant design of structures)
- Bureau of Indian Standards — IS 13920:2016 (Ductile design and detailing of reinforced concrete structures subjected to seismic forces)
- Bureau of Indian Standards — IS 1786 (High strength deformed steel bars and wires for concrete reinforcement); IS 15988 (Seismic evaluation and strengthening of existing RC buildings — guidelines)
- National Building Code of India 2016, Part 6 (Structural Design)
- Price ranges: indicative October 2026 estimates — confirm locally before budgeting
