Spalling is a prevalent issue in the preservation and maintenance of buildings, particularly those of historical value. It refers to the crumbling or flaking off of the surface layer of bricks or other masonry materials, primarily caused by excess moisture and exacerbated by frost action. A sound understanding of spalling, its causes, and potential remedies is crucial for anyone responsible for building maintenance or restoration.

Causes of Spalling

The primary cause of spalling is excess moisture being absorbed by permeable materials like bricks, without adequate evaporation, leading to a cycle of dampness, frost damage, and surface degradation. The sources of this excess moisture can vary:

  • Rainwater Penetration: Due to damaged or blocked guttering and downpipes, leading to overflow onto the masonry below.
  • Coatings: Certain coatings may trap moisture within the bricks, exacerbating the spalling process.
  • Leaks: Water leaks from faulty plumbing or roofing can saturate bricks.
  • Condensation: In some instances, persistent condensation can also contribute to spalling.

Identifying Spalling

Spalling manifests as a visible degradation of the brick or stone surface:

  • Surface Crumbling: The exterior surface crumbles, flakes off, or shows pockmarks.
  • Discoloration: Affected areas might exhibit discoloration due to dampness.
  • Frost Damage: In colder climates, frost damage may be apparent where water has entered the material, frozen, and expanded.

Impact of Spalling

The effects of spalling can extend beyond mere aesthetics:

  • Structural Integrity: Over time, severe spalling can compromise the structural integrity of the building.
  • Insulation Loss: Spalled bricks lose their insulation capabilities, leading to increased energy costs.
  • Aesthetic Deterioration: The visual appeal and historical value of a building can be significantly marred by spalling.

Investigating the Root Cause

Determining the source of excess moisture is pivotal in addressing spalling:

  • Guttering and Downpipes Inspection: Regular inspection, especially during or after rain, can highlight blockages or damage.
  • Water Flow Observation: Observing water flow during a rainstorm can pinpoint areas of concern.
  • Internal Damp Investigation: Spalling can provide clues to internal damp issues that need addressing.

Remedial Measures

While spalling can be remedied to some extent, addressing the root cause of dampness is paramount:

  • Brick Replacement: Damaged bricks can be replaced, or improvements made with absorbent mortar, though this is often seen as a last resort.
  • Moisture Source Rectification: Fixing leaky gutters, downpipes, or other sources of water ingress will help prevent further spalling.
  • Allow Natural Evaporation: If possible, allowing the bricks to naturally dry out over time can also be beneficial.


Spalling is a common yet often overlooked issue that can lead to significant structural and aesthetic problems if left unaddressed. Focusing on identifying and rectifying the sources of excess moisture, rather than merely treating the symptoms, will yield the most enduring solutions. Proper maintenance and timely interventions can preserve the beauty and integrity of buildings for generations to come.

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