House Cracks: How Can You Tell If a Crack in a Wall Is Serious?

More than one in two homes in France is now located in an area with a medium or high risk of cracking, mainly due to periods of drought. Cracks in a house are a legitimate source of concern, as they may reveal a structural problem of varying severity. This article will help you understand the different types of cracks, identify their causes, assess their seriousness, and learn about repair options, insurance coverage, and available remedies. A professional assessment remains essential for obtaining a reliable diagnosis.

What Are the Different Types of Cracks in a Wall?

To properly assess the severity of a crack, it is essential to identify it correctly. Cracks are mainly classified according to their width, orientation, and location. This classification helps determine whether you are dealing with a simple cosmetic defect or a sign of a structural issue requiring prompt action.

The first distinction is based on size: microcracks measure less than 0.2 mm, fine cracks range from 0.2 to 2 mm, and major cracks or deep fissures exceed 2 mm in width. This initial measurement provides a first indication of severity, but it is not sufficient on its own to evaluate the actual risk.

Microcracks, Fine Cracks, and Major Fissures: How to Recognize Them

Microcracks are often linked to the drying of render or plaster. This phenomenon, known as crazing, appears as a network of small superficial cracks affecting only the render layer. They generally result from excess water in the mortar, drying too quickly, or excessive troweling. While harmless to the structure, they remain primarily a cosmetic issue.

Fine cracks, measuring between 0.2 and 2 mm, require closer monitoring. They may affect the entire thickness of the render and sometimes part of the underlying masonry.

If they do not widen over time, they are often harmless, but their evolution should be documented.

Major fissures, which exceed 2 mm in width, are a warning sign. They generally run through the full thickness of the wall and may compromise the watertightness and stability of the building.

When faced with a major fissure, a professional assessment should be carried out quickly to determine its cause and plan the appropriate repairs.

Vertical, Horizontal, and Stair-Step Cracks

The orientation of a crack often reveals its origin. Vertical cracks frequently appear at junctions between two masonry elements, such as adjoining walls or building corners.

They often result from material shrinkage during drying or differential movement between different parts of the building. If they remain thin and stable, they are generally not a major concern.

Horizontal cracks are more worrying. They often indicate lateral pressure on the wall, ground settlement, or foundation issues.

They are frequently found beneath floor slab edges, indicating deformation or rotation of the structure. These cracks require careful monitoring and professional assessment if they evolve.

Stair-step cracks follow the masonry joints, tracing the outline of blocks, bricks, or stones. They generally indicate ground movement or differential settlement of the foundations.

Often wider than 2 mm, they are considered serious and require rapid intervention by an expert to identify the cause and stabilize the building.

Structural and Through Cracks: The Most Dangerous

A crack becomes truly concerning when it is structural, meaning it runs completely through the wall. These through cracks are visible both inside and outside the property, compromising the wall's watertightness and structural integrity. They indicate a structural issue that may threaten occupant safety.

Structural cracks often result from significant movement of the supporting ground, inadequate structural ties between masonry elements, or floor deformations exerting excessive stress on load-bearing walls.

They may be accompanied by other alarming signs: doors or windows sticking, render detaching from the façade, visible water infiltration, or localized floor subsidence.

If you discover a through crack, never attempt to fill it yourself before obtaining a proper diagnosis. Urgent intervention by a structural engineer or independent building expert is essential to assess the true severity of the issue and recommend the necessary stabilization work, which may range from underpinning to the installation of micropiles to stabilize the foundations.

Cracks in Façades, Interior Walls, Ceilings, and Floors

The location of a crack provides valuable clues about its origin. Exterior façade cracks are often the most visible and concerning.

Exposed to the elements, they can encourage water infiltration and worsen existing defects. For example, a horizontal crack on a rendered façade may reveal a foundation problem or pressure exerted by the surrounding ground.

Cracks in interior load-bearing walls require special attention because these walls support the structure of the house. A vertical crack at the corner of a load-bearing wall may indicate differential settlement, while a horizontal crack beneath a floor slab often signals floor deformation.

Ceiling cracks should also be monitored. If they remain superficial and follow plaster joints, they are often harmless.

However, a wide, evolving ceiling crack may reveal a problem with the floor structure or roof framework.

Finally, cracks in flooring or tiles may result from ground settlement, slab movement, or simply poor installation. Tiles that crack or lift are often a sign of instability in the underlying support and should be evaluated by a professional.

Why Do Cracks Appear in a House?

Cracks in a house can have many different causes. Understanding the origin of a crack is essential for assessing its seriousness and choosing the appropriate repair solution.

Four main categories of causes dominate: ground movement linked to climatic conditions, construction defects, natural aging of materials, and work carried out nearby or on the building itself.

Drought and Clay Soil Movement

The shrink-swell phenomenon of clay soils is now the leading cause of cracking in France. When clay soil undergoes significant changes in moisture content, it behaves like a sponge: it shrinks during drought periods and expands when rain returns.

These differential ground movements place stress on foundations, causing cracks in walls and façades.

Between 2018 and 2022, approximately 240,000 claims related to clay soil shrink-swell were reported in France, representing 58% of all claims recorded since 1989. With climate change, drought periods are becoming more intense, mechanically increasing the number of affected homes.

A national map updated in 2026 now identifies areas with low, medium, or high exposure to the shrink-swell phenomenon. The regions most affected include many departments in southwestern, central, and eastern France, where surface clay formations are particularly sensitive.

Localized ground subsidence caused by drought can lead to differential settlement that gradually weakens the structure. Water infiltration often worsens the phenomenon by further altering the moisture content of clay soils.

Construction Defects in New Homes

In a recently built property, the appearance of cracks may reveal poor workmanship or design defects. The most common causes include defective materials, missing or insufficient horizontal or vertical reinforcement ties, foundations unsuited to the soil type, or inadequate drainage around the building.

A properly designed and installed reinforcement system strengthens masonry cohesion and limits cracking risks caused by ground movement. Its absence or poor installation constitutes a serious construction defect.

Likewise, shallow foundations or foundations that do not comply with prior geotechnical studies can lead to differential settlement and structural cracking within the first few years.

Fortunately, the ten-year structural warranty protects homeowners against such defects. It covers, for ten years after completion, damage that compromises the building's structural integrity or renders it unsuitable for its intended purpose.

Significant structural cracks fall within this framework. The builder is therefore required to repair the damage, and this liability is a matter of public policy: no contractual clause can exclude or limit this warranty.

Aging of Older or Stone Houses

The passage of time naturally affects all construction materials. In older homes, cracks may result from the gradual aging of brick, concrete block, or stone.

Masonry joints, exposed to weather conditions and freeze-thaw cycles, wear out and weaken, losing their ability to absorb minor structural movements.

Progressive foundation settlement is a common phenomenon in older buildings. Over decades, the soil beneath the foundations slowly compacts, sometimes causing localized subsidence that appears as stair-step cracks along joints or vertical cracks in load-bearing walls.

In stone houses, the absence of modern reinforcement systems makes the structure more vulnerable to differential movement. Repeated water infiltration also weakens traditional lime mortars, accelerating deterioration and the appearance of fine and then deeper cracks.

Cracks Following Nearby Construction Work or Between a House and an Extension

Work carried out on a neighboring property can cause cracks in your home. Vibrations generated by nearby construction, excavation work affecting ground stability, or the demolition of a shared wall are all potential risk factors.

Cracks generally appear soon after the work begins, making it easier to establish a causal link.

The addition of an extension that is poorly connected to the existing structure is also a common cause of cracking. If the new section rests on different foundations or no expansion joint has been provided, the two parts of the building will react differently to temperature variations or ground movement.

Vertical cracks then appear at the junction between the old and new structures.

In the event of damage caused by neighboring works, you may invoke the principle of abnormal neighborhood disturbance. This civil liability action allows you to obtain compensation regardless of fault, as the owner of the property causing the disturbance is strictly liable.

It is essential to quickly gather evidence: dated photographs, a bailiff's report, and a technical assessment establishing the connection between the work and the cracks. An amicable approach with the neighbor or their insurer is recommended first. If unsuccessful, legal action may be pursued to obtain compensation for the damage.

When Should You Be Concerned About a Crack in a Ceiling or an Exterior Wall?

Assessing the seriousness of a crack requires considering several factors: its width, depth, progression over time, orientation, and location. A fine, stable crack in façade render does not have the same implications as a deep crack that is rapidly widening in a ceiling or load-bearing wall.

Signs of a Serious Crack in Render or Tilework

Certain warning signs should immediately raise concern. If you notice that a crack is widening over the course of several weeks, it indicates that the structure is still moving.

A through crack, visible both inside and outside the wall, indicates a serious structural issue that requires prompt intervention.

Other symptoms should also attract your attention: a door or window that suddenly becomes difficult to open, render detaching from the façade, tiles cracking or lifting, or visible water infiltration around the crack. These signs often indicate ground movement or foundation settlement.

To monitor a crack's progression, a plaster tell-tale remains a simple and effective method. This involves applying a small plaster marker across both sides of the crack and writing the installation date on it.

If the marker breaks, it confirms that the crack is continuing to evolve and that action should be taken without delay.

What Should You Do If You Find a Crack in Your Home?

As soon as suspicious cracks appear, adopt the right practices to document the situation. Take dated photographs and precise measurements using a ruler to record the width and length of each crack.

This documentation will be invaluable for monitoring changes over time and for discussions with professionals.

Install a plaster or glass tell-tale on the most concerning vertical or horizontal cracks and check it regularly. Above all, never fill a crack before obtaining an accurate diagnosis of its nature and cause.

A simple cosmetic repair only conceals the issue without solving it and may even complicate future assessments.

If you have any doubt about the severity of a crack, contact a building expert or structural engineer promptly. Their diagnosis will determine whether the deep cracks observed are merely due to normal material aging or indicate a more serious issue requiring structural repairs.

Which Professional Should You Contact for a Crack Assessment?

When cracks appear in your home, it is essential to consult a qualified professional before carrying out any repairs. An accurate diagnosis helps identify the cause of the defects, assess their severity, and determine the appropriate corrective work. But who should you contact to obtain a reliable assessment?

The Role of a Crack Expert and Structural Engineer

Several professionals can assist you in analyzing cracks. An independent building expert specializes in building pathology and performs a comprehensive diagnosis of your property.

They examine the shape, location, and depth of cracks to determine their origin and recommend appropriate repair solutions. Unlike an expert appointed by your insurance company, who works on behalf of the insurer, an independent expert represents your interests and provides a detailed assessment report.

A structural engineer becomes involved when cracks affect load-bearing elements of the building, such as foundations, load-bearing walls, or beams. They carry out an in-depth structural analysis and may prescribe additional testing, including stability measurements and foundation inspections.

A technical engineering consultancy may also be consulted for complex cases requiring structural calculations or geotechnical studies.

If you are considering purchasing a cracked property, obtaining an expert assessment before signing the deed of sale is essential. It allows you to negotiate the price with full knowledge of the situation and anticipate any necessary repair work.

How Much Does an Assessment Cost?

The cost of a crack assessment generally ranges between €500 and €1,500 in 2026, depending on several factors. The size of the property directly affects the fee, as do the accessibility of the areas to be inspected and the number of cracks requiring analysis.

For a standard detached house, expect to pay between €800 and €1,200. More complex cases requiring extensive investigations or a second opinion can exceed €2,000.

Several factors influence pricing: geographic location (fees are often higher in the Paris region), the expert’s reputation and experience, and the type of report requested (a simple diagnosis or a legally enforceable report).

In the event of a natural disaster officially recognized by government decree, the assessment may be covered by your home insurance policy. It is advisable to request several detailed quotes and verify the expert’s qualifications and professional liability insurance before proceeding.

How Do You Repair a Cracked Wall in a House?

The repair method depends primarily on the type of crack and its cause. Before undertaking any work, it is essential to obtain a professional diagnosis to identify the source of the issue.

A superficial crack caused by render drying will not require the same solution as a structural crack resulting from foundation settlement.

Common Repairs: From Filling to Masonry Work

For microcracks and superficial cracks (less than 2 mm), light repairs are generally sufficient. Filling with repair compound or acrylic sealant can effectively close these small openings.

Applying reinforcing tape or fiberglass mesh before the finishing coat helps prevent the crack from reappearing.

Structural cracks, however, require more extensive masonry work. Masonry repairs involve removing damaged sections and rebuilding the affected area.

Injecting epoxy or polyurethane resin fills deep cracks and stabilizes the structure by penetrating the smallest gaps within the wall. Installing horizontal or vertical reinforcement ties strengthens the cohesion of the entire building.

Floor reinforcement may also be necessary when cracks result from uneven load distribution.

Micropiles and Underpinning: Costs and Solutions

When a house is settling due to defective foundations or unstable ground, micropiles are often the preferred solution. These small-diameter deep foundation elements (typically less than 30 cm in diameter) are drilled into the ground until they reach a stable load-bearing layer, often between 5 and 30 meters deep.

They transfer the building’s loads to stronger soil and stop further movement.

Underpinning becomes necessary in cases of significant differential settlement, severe stair-step cracks, or visible structural subsidence. This major intervention aims to strengthen or rebuild existing foundations.

Expect costs ranging from €10,000 to €50,000 for a complete intervention, with micropile prices between €250 and €500 per linear meter under standard conditions, and up to €800–€1,200 per linear meter on complex clay soils.

For a 100 m² detached house, around twenty micropiles may be required, representing a significant investment.

How Much Does Repair Cost and Which Company Should You Hire?

The cost of repairing a crack can vary enormously. Simple filling of a microcrack may cost only a few dozen euros in materials if carried out yourself.

Professional metal stitching of a 2 to 5 mm crack generally costs between €20 and €100 per m². Resin injection for deep cracks ranges from €50 to €150 per linear meter.

For major structural work such as underpinning, micropiles, or foundation reinforcement, costs can reach tens of thousands of euros.

When dealing with cracks, hire a company specializing in masonry repairs or foundation stabilization. Always request several detailed quotes outlining the proposed methods, materials, and intervention timelines.

Verify that the company carries professional liability insurance and a ten-year structural warranty. For major projects, hiring a project manager may be advisable to coordinate the work and ensure quality control.

Does Home Insurance Cover Cracks?

Home insurance does not automatically cover all types of cracks. Coverage depends on the cause of the damage and the guarantees included in your policy.

In most cases, cracks resulting from natural aging, lack of maintenance, or purely cosmetic defects are not covered.

However, your comprehensive home insurance policy may provide coverage when cracks result from a natural disaster officially recognized by an interministerial decree, such as severe drought causing clay soil shrink-swell, flooding, or landslides. This natural disaster guarantee is automatically included in insurance contracts that cover property damage.

It may also apply when water damage causes structural cracking.

How to Report a Crack to Your Insurance Company

As soon as you notice a crack, start by checking whether a natural disaster decree has been issued for your municipality. This information is available from your local town hall or on the Official Journal website.

If your area is covered by such a decree, you have 10 working days from the publication date to report the claim to your insurer.

Your claim should be sent by registered mail with acknowledgment of receipt. Include a detailed description of the damage, dated photographs showing the progression of the cracks, and, if possible, an initial technical assessment.

Carefully document the condition of the property before any repairs are carried out to facilitate the subsequent expert assessment.

For other types of claims (outside the natural disaster framework), the reporting deadline is generally five working days. Respecting these deadlines is essential, as late notification may result in a loss of coverage and therefore no compensation.

Compensation Amounts and New Regulations on Cracks

The amount of compensation varies depending on the nature and extent of the damage. Your insurer will generally appoint an expert to assess the required repairs and estimate the cost of the work.

A statutory deductible always applies: €1,520 for cracks caused by drought and clay shrink-swell phenomena, and €380 for other natural disasters.

Since the reform of the French Natural Disaster Compensation Scheme (CatNat), which came into force in 2024, the criteria for recognizing a state of natural disaster have been relaxed to improve compensation for affected property owners. The reform notably facilitates coverage for damage caused by clay soil shrink-swell, which affects more than 10 million homes in France.

A February 2023 ordinance now requires homeowners to use insurance compensation to repair their cracked property. This obligation is waived if the cost of repairs exceeds the value of the property or if the building has become uninhabitable.

These changes are intended to accelerate repair work and preserve the structural integrity of buildings. In cases where a cracked property is considered unsellable in its current condition, the regulations now provide a stricter framework for property transactions.

What Remedies Are Available for a House That Is Sinking?

If your house is subsiding and showing severe structural cracks, several remedies may be available depending on the age of the property.

For a newly built house less than 10 years old, the builder's ten-year structural warranty covers damage that compromises the solidity of the building or renders it unfit for its intended purpose.

You must report the damage as soon as it is discovered and no later than two years after becoming aware of it, providing photographs and supporting evidence.

The perfect completion guarantee, which applies during the first year following completion of the construction works, obliges the builder to repair any cracks reported during that period, whether structural or cosmetic.

If you purchased a structural damage insurance policy (dommages-ouvrage) when the house was built, you may obtain rapid compensation, often within 15 days and without any deductible.

For an older house that is subsiding, recourse generally involves your home insurance policy if a natural disaster decree has been issued.

You may also bring an action against the seller for latent defects within two years of discovering the issue, provided you can prove that the cracks existed before the sale and were not disclosed.

Seek assistance from a Capifrance advisor to assess the impact of cracks on your property's value and to guide you through the necessary procedures.

FAQ About House Cracks

Should You Buy a House with Cracks?

Buying a house with cracks is entirely possible, provided that you obtain an independent technical assessment beforehand. This diagnosis will help identify the nature and severity of the cracks, estimate the cost of necessary repairs, and allow you to negotiate the purchase price accordingly.

In general, a house with structural cracking may suffer a discount of 20% to 30% compared to market value.

A Capifrance advisor can help you obtain an accurate valuation and secure your purchase project.

At What Compensation Amount Will the Insurance Company Send an Expert?

French law does not establish a specific minimum threshold requiring an insurance company to appoint an expert.

However, insurers generally commission an expert once the estimated damage exceeds approximately €3,000.

The purpose of the assessment is to determine the cause of the damage, accurately estimate repair costs, and prevent fraud.

In cases of officially recognized natural disasters, an expert assessment is systematic regardless of the amount involved.

The expert will visit the property, inspect the cracks, assess their severity, and prepare a report that serves as the basis for compensation.

Is a Cracked House Unsellable?

No, a cracked house is not necessarily unsellable, but transparency is a legal obligation for the seller.

You must inform potential buyers of the existence of the cracks and their origin in the deed of sale, otherwise you may be exposed to claims for latent defects.

An older house with cracks will generally experience a reduction in value, but it can still be sold, particularly if a technical assessment has been carried out and the necessary repair costs have been clearly identified.

Providing a professional expert report reassures buyers and helps facilitate negotiations by establishing an objective basis for discussing the property's condition and value.

Author :

Frédéric Rémy – Director of Commercial Performance
A real estate professional for several years within the Capifrance network, I would like to share with you some essential advice to help you succeed in your real estate project with the support of our advisors.