# Stair-step cracks on an old facade in Nice: cause and severity

> Stair-step cracks on an old Nice facade can signal serious structural movement. Learn how to assess severity before repairs worsen the damage.

- URL : https://cassini-expertise.fr/en/stair-step-cracks-old-facade-nice/
- Langue : en-US
- Mis à jour : 2026-11-06
- Site : Cassini Expertise (https://cassini-expertise.fr/)

**See a real case.** [Facade cracks and rainwater drainage – Cannes](https://cassini-expertise.fr/en/facade-cracks-drainage-diagnosis-cannes/) : 16 cracks catalogued, drainage review, clay shrink-swell context.

## Stair-step cracks on an old facade in [Nice](https://cassini-expertise.fr/nice-secheresse-argile-fissures-donnees-officielles/): cause and severity

You’re looking at the wall of your old house in Nice, and you see that crack climbing diagonally, like a staircase. It wasn’t there two years ago. Honestly, that’s never trivial. In practice, a stair-step crack following the mortar joints is often a sign of differential movement between two parts of the wall. DTU 20.1 (NF P 10-203) states that façade masonry must withstand loads without structural disorder. As soon as you step outside that framework, you need to understand why.

## Telling an active crack from a stabilised one

The first question: is it still moving? A stabilised crack is often old, a settling from the early years. An active crack is something else. Simple test: place a fine plaster tell-tale (or just a pencil line) across the crack. Write the date. Check every three months. If the line breaks, it’s still working. A crack gauge costs a few dozen euros and gives a measurement in millimetres. That’s the basis before any conclusion.

In Nice, old houses in the Vieux-Pays or hillside districts like Cimiez or Mont Boron are often founded on heterogeneous ground. BRGM has mapped clay-rich areas sensitive to shrink-swell in the Alpes-Maritimes. Soil that swells in winter and shrinks in summer works the foundations. And a façade follows.

## The most common causes on a Nice house

There are three families of causes. First, foundation movement: clay shrink-swell, poor bearing capacity, or shallow footings on sloping ground. Second, water: a blocked rainwater downpipe, repeated infiltration, poorly directed runoff. Water pooling at the base of a wall is a classic. Third, nearby works: an excavation next door, earthworks that destabilise.

On an old house, materials are often soft (limestone, lime mortars). They cope less well with movement. A stair-step crack crossing several stone courses generally indicates differential movement, not simple crazing. Crazing is superficial: a fine network, no offset. If you run your hand over it and feel a step, you’re in a different category.

## How to assess severity without fooling yourself

Three criteria matter. Width: below 0.2 mm, it’s often cosmetic. Between 0.2 and 2 mm, monitor it. Above 2 mm, especially if it’s evolving, you’re in structural territory. Continuity: a crack running from the ground up to the roof across floors is more serious than a local crack under a window. Offset: if the two edges are no longer in the same plane, the movement is real.

Honestly, the only opinion that counts is from a professional who comes to see it. A façade diagnosis is an hour on site, a survey, and a clear conclusion. Don’t settle for a remote patching quote.

## What to do in practice

1. Set a tell-tale and photograph it with a ruler for scale. Date everything. 2. Check rainwater drainage: gutters, downpipes, inspection chambers. A blocked downpipe can be enough to explain a disorder. 3. Don’t patch immediately. Patching an active crack hides the problem, it doesn’t treat it. 4. If the crack evolves or exceeds 2 mm, call in a building expert or a structural engineering firm. 5. If a neighbour has done recent works, document the timeline.

## Recourse and guarantees

If the house is under ten years old, the [ten-year guarantee](https://www.service-public.gouv.fr/particuliers/vosdroits/F2034) may apply ([Article 1792](https://www.legifrance.gouv.fr/codes/article_lc/LEGIARTI000006443502) of the French Civil Code). For an old house, it’s a different regime. You can pursue the company that carried out recent works if the disorder is attributable to them, on the basis of contractual liability. In a dispute with a neighbour over works that destabilised your wall, Article 1244 of the Civil Code (formerly 1386) may be invoked. And if the disorder stems from a recognised natural hazard, natural disaster insurance may apply after an interministerial decree. In Nice, decrees for ground movement are not rare. Keep all evidence: dated photos, tell-tales, invoices.

## Frequently asked questions

### Is a stair-step crack always serious?

No. A fine, stabilised crack can remain cosmetic for years. What matters is its evolution and width. Above 2 mm with offset, you should consult.

### How do I know if my crack is still moving?

Place a tell-tale (plaster or pencil line) across it, date it, and check every three months. If the tell-tale breaks, the crack is active. A crack gauge gives a more precise measurement.

### Can I patch it myself?

Patching an active crack without treating the cause is a bad idea: it will reappear. Wait for the diagnosis. If it’s stabilised and superficial, a suitable flexible mortar may suffice.

## Further reading

- [My terrace exceeds the permitted ground coverage in Nice: risks and regularisation](https://cassini-expertise.fr/terrasse-depasse-emprise-au-sol-autorisee-nice-risques-regularisation/)
- [A crack that is getting wider: should I be worried?](https://cassini-expertise.fr/une-fissure-qui-sagrandit-dois-je-minquieter/)
- [Right of way in Grasse: disputed width, tacheometer measurement](https://cassini-expertise.fr/servitude-passage-largeur-contestee-mesure-tacheometre-grasse/)

**See also:** [Diagonal cracks above windows in Toulon: differential foundation settlement](https://cassini-expertise.fr/en/diagonal-cracks-above-windows-foundation-settlement-toulon/) · [Structural or Superficial Cracks: How to Tell the Difference](https://cassini-expertise.fr/en/structural-vs-superficial-cracks/)

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Source : https://cassini-expertise.fr/en/stair-step-cracks-old-facade-nice/