Most cracks in Indian buildings are surface events — plaster and thermal movement. A minority are structural, and the skill every owner needs is telling the minority apart. Fill a hairline and life goes on; fill a structural crack and you have silenced a smoke alarm.
The visual tests
| Look at | Likely surface crack | Take seriously |
|---|---|---|
| Width | Hairline — a fingernail does not catch | Wide enough to hold a coin edge, or widening over months |
| Pattern | Random maps, crazing, short runs | Long continuous lines; stepped along brick joints; diagonals from corners of openings |
| Depth | In the plaster — masonry behind intact | Through plaster into masonry; visible both sides of a wall |
| Displacement | None — faces flush | One side proud of the other; doors/windows newly jamming nearby |
| Behaviour | Stable year to year | Growing, or reopening promptly after each repair |
What each needs
Surface cracks
Cosmetic-to-preventive repair: rake, fill, redecorate on walls; on roofs and terraces they are also water paths, so the fill-and-seal method applies (the four steps). Maps of hairlines on exposed slabs are the standard case for elastic coating systems (question one).
Structural signals
Assessment before filler — a structural engineer's visit, with your photographs and dates as evidence. Causes range from settlement to overloading to corroding reinforcement (rust staining raises urgency); remedies are theirs to prescribe. Cosmetic filling first destroys the diagnostic evidence and delays the real answer.
The monitoring habit
Unsure which you have? Date a pencil line across the crack's end and width-mark it; photograph monthly. Stable for seasons — treat as surface. Growing — you now hold exactly the evidence an engineer needs. Uncertainty with growth is a call to make, not a filler purchase.
Frequently asked questions
Are corner diagonals over doors always structural?
Common stress points — often minor lintel movement, occasionally more. Width, depth and growth decide; monitor and judge by the table.
My new house shows fine cracks everywhere. Panic?
First-year hairline crazing as construction moisture leaves is common and settles. Watch widths; treat cosmetically once the building has finished its first breath.