cracks and structural movement: causes, structural risk and monitoring

cracks and structural movement are one of the pathologies that cause the most concern to the user, and with good reason: although many are aesthetic and of little relevance, others may indicate structural problems that require intervention. The role of the expert is to distinguish one from the other, identify the cause and establish, where appropriate, follow-up to confirm whether the injury is stabilized or continues to evolve.

Crack versus crack: technical nuance

In construction practice, we usually speak of a crack when the opening is superficial and of limited width, and of a crack when it affects the entire thickness of the element and has a greater width. Although the nuance depends on the context, the crack usually entails a more demanding analysis due to its possible structural implication.

Common causes

The most frequent causes are:

• Shrinkage of the mortar or concrete during setting, generally aesthetic.
• Hygrothermal changes that produce cyclical expansions and contractions.
• Differential terrain settlements, which can generate characteristic patterns.
• Surcharges due to poorly planned renovations, changes of use or elimination of functional partitions.
• Execution defects: poor quality of the mortar, insufficient reinforcement, absent expansion joints.
• Pushes and humidity that degrade the material and cause openings.

Characteristic patterns

An experienced expert interprets the crack pattern to guide the cause. Some examples:

• Cracks at 45º near gaps: differential settlements or loads.
• Horizontal cracks in encounters: material changes or dilations.
• Fine and branched cracks: superficial retraction.
• Continuous vertical cracks: possible structural movement.

This analysis must always be complemented with objective measures.

Monitoring with witnesses and crackmeters

When the crack may be active, plaster cores, scale cores or fissurometers are installed to measure its evolution over time. A follow-up of several weeks or months provides key information:

• If the witness breaks, the crack continues to move.
• If the crackmeter registers seasonal variations, the cause is hygrothermal.
• If the width increases steadily, it is necessary to investigate in depth.

When is it urgent

It is prudent to act without delay when:

• Wide and continuous cracks in structural elements.
• Cracks in beams, pillars or slabs.
• Visible shifting, giving or creaking.
• Rapid worsening in a few weeks.

In these cases, in addition to expert report, it may be necessary to coordinate with a structural technician and take precautionary measures.

Related links

To know the instruments and tests used, see Technical tests. For legal deadlines, review Decennial, Triennial and Annual Guarantee and consult your attorney. to commission the report, go to Contact or the specialty of Defective workmanship.