Cracks in Walls in Delhi: Which Ones Actually Matter

How to read a crack in five minutes

Before anyone quotes you, gather these five facts. They are free, and they are what a competent professional will ask you anyway.

• How wide is it? Use something you have: a visiting card is roughly half a millimetre thick, and the edge of a small coin is a couple of millimetres. Very fine cracks you can barely catch a fingernail in are a different conversation from cracks you can push a card into.
• Does it go through the plaster or into the wall? Scratch gently along it. If the plaster edges crumble and it stops there, it is a surface crack. If it continues into the brick or concrete behind, that is a different category.
• Which way does it run? Fine random cracks in a web or map pattern are shrinkage in the plaster or the paint. Straight vertical cracks at a door or window corner are usually joint or settlement movement. Diagonal cracks running through masonry, especially widening as they go, are the pattern that deserves an engineer.
• Is it on both faces of the wall? Go into the next room and look at the same spot. A crack visible on both sides has gone through the wall, not just the plaster.
• Is it moving? Mark both ends with a pencil and the date, or bridge it with a strip of paper glued at both ends. Check in a month, and again after a season change. A crack that has not moved is far less interesting than one that has.

Hairline cracks: the ordinary kind

These are the majority, and they are a decorating problem rather than a building problem. They come from the surface layers shrinking and moving, not from the structure.

• Map or crazing cracks. A fine web across a patch of wall or ceiling, often looking like dried mud. Usually plaster that dried too fast or a rich cement mix. Very common on walls that take direct afternoon sun in a Delhi summer.
• Shrinkage cracks in new plaster or POP. New work releases moisture as it cures, and a bit of cracking as it does so is normal. This is why plaster is supposed to cure before painting rather than be painted the same week.
• Cracks in the paint film only. Fine lines that follow no logic, sometimes with flaking at the edge. Often too many coats built up over years, or an incompatible layer underneath, such as emulsion over old distemper.
• Thermal cracks near the ceiling on a top floor. The roof slab expands in the heat and contracts at night, and the top of the wall takes that movement. Extremely common in Delhi top-floor flats and usually cosmetic on its own — but worth checking for damp, since a crack in that position is also a route for water.

The repair for all of these is the same: rake the crack open slightly so the filler has something to grip, fill, sand flat, prime the patch and repaint the full wall. Our wall putty and primer guide explains what putty does and when it is genuinely required.

Cracks at joints and corners: predictable, and they come back

Some cracks appear in exactly the same places in flat after flat, because they sit where two different materials meet and each material moves at its own rate.

• Along the line where a beam or column meets brickwork. Concrete and brick expand differently in Delhi heat, and the plaster spanning the joint splits. A straight crack that follows a structural outline is usually this.
• At the top corners of doors and windows. A short crack running diagonally up from the corner of an opening is one of the most common cracks in any building, because the corner is a weak point in the plaster.
• Where a POP false ceiling meets the wall, or along the joints between boards. False ceilings move slightly and the joint shows it. See our POP false ceiling guide.
• Around a chased wall where a pipe or electrical conduit was buried. The refilled channel shrinks differently from the wall around it and reappears as a straight line.

The honest thing to know about these: a plain putty fill will usually crack again, because the movement that made it has not stopped. Repairs that last generally involve opening the crack out, using a flexible filler and bedding a mesh or fibre tape across the joint before skimming over it. If a painter offers to simply skim over a joint crack that has already returned twice, ask what they are doing differently this time.

When should I actually worry about a crack?

Structural cracks are a small minority, but they have recognisable signatures. Treat any of the following as a reason to get a qualified structural engineer to look, rather than a painter:

• Diagonal cracks that get wider along their length, particularly running through masonry from a corner, or stepping through the mortar joints of a brick wall.
• Cracks in a column, beam or slab itself rather than in the plaster covering it — especially if any concrete has spalled off, or you can see rusted reinforcement bars.
• A crack you can see on both faces of the wall and that has clear depth, or that lets light or draught through.
• Cracks that are measurably growing over weeks, against a pencil mark or a paper strip.
• Cracks with other symptoms alongside: doors or windows that have started to bind, floors that feel out of level, a gap opening between a wall and the floor or ceiling.
• New cracks that appeared suddenly, after nearby construction, deep excavation, borewell work, or heavy structural alteration in the flat below or next door. In Delhi NCR this last one is worth taking seriously, because internal walls get knocked out during renovations more often than anyone admits.

This is not something to solve on the internet. An engineer looks at the whole building, not one wall. Filling and painting a structural crack does not stabilise anything — it just removes your ability to see whether it is still moving.

Cracks, water and the Delhi monsoon

Even a cosmetic crack matters if it is on the outside of the building, because a crack is a route for water. This is where a small painting job turns into a damp problem.

• Exterior wall cracks feed monsoon water into the masonry. Driven rain finds a fine crack easily, soaks into the wall over days, and shows up as a damp patch or peeling paint on the inside face. Sealing exterior cracks before the rains is one of the highest-value things you can do — see our exterior painting guide.
• Terrace and parapet cracks are worse, because water stands on a flat roof rather than running off it. A crack at the junction of the terrace and the parapet wall is one of the classic sources of top-floor leaks. Our terrace waterproofing guide covers this.
• A crack with a stain around it is not a crack problem any more. Brown edges, a white salty bloom or soft plaster mean water is already coming through. Fill it and you have sealed water inside the wall.
• Check cracks before the monsoon, not during it. Filling and sealing work needs dry weather to cure. Our monsoon waterproofing tips and the monsoon home maintenance checklist cover the timing.

If damp is already showing, deal with that first: our guides on wall seepage and on paint peeling off walls take it from there.