Apartment building, house, structure… crack risks in older buildings
A crack in an older building may indicate a simple plaster defect, but it can also signal a progressive structural issue. In an old house or a condominium apartment building, monitoring how a crack evolves helps distinguish an active instability from a stabilized defect, before any intervention. This step is key to a reliable assessment, the safety of the structure, and the relevance of repair works.
Saugnac gauges provide precise, discreet solutions compatible with traditional materials, tailored to the requirements of older buildings and the constraints of non-destructive interventions.
Older buildings: what cracks reveal about the condition of the structure
Cracks—depending on their shape, location, and evolution—provide information on the nature and severity of defects in older buildings.
Important note: The elements below are provided for information purposes only. They do not constitute a diagnosis nor a definitive analysis guide. Each cracking situation is specific. To establish a reliable diagnosis and decide on any interventions, it is essential to consult a qualified building professional (structural engineer, independent expert, engineering office, etc.).
Different types of cracks frequently observed
Cracks in older buildings vary depending on their orientation:
- Vertical cracks may be related, among other causes, to differential settlement of the ground beneath the foundations or to shrinkage phenomena in materials (masonry, renders, mortars).
- Horizontal cracks can indicate internal pressures (soil pressure on a basement wall, localized overload) or expansion/shrinkage effects when stresses are not properly accommodated;
- Stair-step cracks, which generally follow masonry joints (bricks, rubble stone, blocks, stones), are often associated with differential movements of the structure or foundations (settlement, clay shrink–swell, soil heterogeneity)
- Diagonal cracks, common around openings (under lintels or at window/door corners), may reveal stress concentration near these areas (insufficient bearing, undersized lintel, recent opening modification) or, more broadly, a local weakness of the structure
The shape, location, and evolution over time of these cracks are only a first indicator. Their interpretation must always be put back into the overall context of the building and confirmed by an independent assessment before any decision to carry out works.
Differential shrinkage and bending: structural causes often mentioned
In older buildings, several structural phenomena can be associated with the appearance of cracks. Unlike recent structures, cracking observed in older buildings rarely results from mortar shrinkage that is still ongoing. More often, it results from cumulative movements and differentiated behavior between materials.
Timber floors — common in older buildings — can deform over time due to: creep, natural aging, loads not foreseen during construction, insufficient or weakened bearing. Such deformation can cause rotation at the wall bearing point, leading to the appearance of horizontal cracks on the façade.
In buildings constructed before modern standards (DTU 20.1), it is common for horizontal ring beams to be absent, vertical ties to be missing at corners, or for local repairs to have been carried out without proper bonding.
Old walls are often heterogeneous: rubble stone, stone, bricks, various infill materials, and concrete elements added over time. Differences in behavior with respect to moisture or temperature can create weak points where cracks develop.
These phenomena often evolve slowly, sometimes with no immediate visible sign, which reinforces the value of monitoring.
Moisture-related pathologies and defects linked to modern renders
Old masonry — bricks, rubble stone, or stone laid with lime mortar — is by nature permeable to water vapor. Applying cement-based renders or impermeable coatings can block this natural breathability.
Moisture trapped in the wall can then cause various defects: render swelling, efflorescence, loss of adhesion, and potentially cracking. These cracks are not necessarily structural, but they can reveal incompatibility between old materials and modern products.
On façades, these phenomena are intensified by thermal variations, exposure to rain, or rising damp.
Associated risks: infiltration, destabilization, silent progression
Even when the opening seems minimal, a crack can facilitate water ingress and locally weaken the structure.
Water penetration can deteriorate joints or bedding layers, increase internal stresses during freezing periods, and accelerate degradation. Some cracks evolve slowly, with no visible external sign, but may indicate deep differential movement (e.g.: settlement, sliding).
In older buildings, sometimes poorly monitored, these developments can go unnoticed until more visible defects appear. Regular monitoring helps to better understand the situation and to alert, if necessary, the professionals responsible for the assessment.
Monitoring cracks to secure the analysis and avoid intervention errors
Monitoring over time can help distinguish a superficial crack from an evolving structural movement.
A crack can be active or stabilized: visible signs are not enough
A fine, old crack may seem harmless, but if its opening changes, it may indicate an ongoing phenomenon. Conversely, a wide crack may have been stable for a long time.
Visible characteristics alone (opening, path, length) generally do not make it possible to determine the nature or activity of the defect. Only instrumented and regular monitoring can reveal its real behavior over time.
From what size should a crack be monitored?
There is no absolute rule regarding the size from which a crack must be monitored. The need for monitoring always depends on:
- the structural context of the building,
- the crack location (corner, lintel, junction between materials, load-bearing area…),
- its shape,
- its age,
- and its behavior over time.
In some cases, a very fine crack located in a sensitive area may justify monitoring. It is therefore neither size alone nor visual appearance that allows a decision.
Evolution over time remains the determining criterion for distinguishing a superficial defect from a structural movement.
If there is any doubt about whether to instrument a crack or not, it is recommended to consult a qualified professional (structural engineer, building expert, engineering office), who can determine the areas to monitor and the appropriate methods.
Instruments suited to crack monitoring on older buildings
Setting up monitoring in older buildings requires devices adapted to fragile materials and installation constraints. Saugnac solutions have been designed to address these specificities.
Installation without drilling: a priority
In older buildings, substrates are often heterogeneous, fragile, or sensitive to vibration. Drilling can cause spalling or local debonding.
Saugnac gauges offer installation without drilling, whether for mechanical gauges (G1 type), digital (E1 type), or connected (R1 type), ensuring secure hold without altering the masonry.
Measuring the evolution of a crack in a stone wall or masonry
The E1 gauge, removable and not permanently fixed to the substrate, is used with transparent mounting plates fastened with simple 4 mm screws or, if necessary, by bonding. This assembly makes it possible to accurately measure crack opening and shear displacement, including on irregular substrates.
It adapts to old masonry, often irregular, and offers excellent stability under climatic variations. On stone buildings as well as rendered façades, this solution provides reliable readings with great simplicity.
A discreet gauge compatible with occupied buildings
In condominiums, apartment buildings and occupied houses, you need to rely on discreet, non-invasive, and easy-to-remove devices.
Saugnac solutions, such as the E1 gauge, meet these requirements: transparent mounting plates, no protruding elements, easy removal of the plates. They integrate into a façade renovation plan or a technical audit.
This compatibility with occupied environments is an asset for property managers and building administrators.
Connected solutions for continuous and remote monitoring
Connected sensors automate data collection and improve responsiveness to developing defects. They fit into a long-term asset management approach.
Reducing manual interventions thanks to autonomous sensors
When monitoring a crack in a condominium building or an occupied older building, multiplying manual readings can become constraining.
Saugnac connected sensors, such as the R1 crack monitor, automatically collect data, with secure transmission to an online platform. Powered by a long-life battery (up to 8 years of autonomy), they remain in place for several years without intervention, reducing travel costs and disturbance for occupants.
Monitoring hard-to-access or sensitive areas
Cracks located at height, on rear façades, or in basements are often complex to inspect regularly. Connected sensors transmit their measurements in real time. This monitoring is particularly useful in condominiums and older buildings, where some areas are inaccessible without a boom lift, scaffolding, or disruption of use.
A dedicated application to visualize and share readings
The Saugnac application centralizes all collected data and ensures traceability. It allows users to track crack evolution over time, generate automatic alerts if thresholds are exceeded, and share readings with engineering offices, architects, or court experts. This digital tool turns crack monitoring into a collaborative, reliable, and well-documented process.