Bricks are not materials that typically become porous over time; rather, they are inherently porous from the moment they are manufactured. This porosity is a fundamental characteristic of many mineral building materials, including brick, stone, and render.
Understanding Brick Porosity
The porous nature of bricks stems from their composition and the manufacturing process. Made primarily from clay or shale, bricks are formed and then fired in a kiln at high temperatures. This firing process creates a hard, durable material but also leaves behind microscopic voids or pores within the brick's structure. It is these tiny spaces that make the brick porous.
As stated in the reference, mineral building materials such as brick, stone and render are all porous meaning they absorb moisture. This inherent porosity allows bricks to interact with their environment, particularly with water.
The Impact of Water Absorption (Water Ingress)
Because bricks are porous, they are susceptible to absorbing moisture from rain, groundwater, or even humidity. This absorption is commonly known as water ingress. The reference highlights that spalling bricks are primarily caused by water absorption, otherwise known as water ingress.
Water entering the pores can cause several issues over time, especially when combined with freeze-thaw cycles or dissolved salts. While the brick itself doesn't become porous due to water, the presence of water within the existing pores can lead to damage that might make the surface appear more deteriorated or affect its structural integrity.
Consequences of Porosity and Water Ingress
The inherent porosity of bricks, combined with water ingress, can lead to various problems:
- Spalling: As mentioned in the reference, this is a common issue where the face of the brick flakes, peels, or crumbles off. This often occurs when absorbed water freezes and expands within the pores, or when salts crystalize, exerting pressure on the brick material.
- Dampness: Water absorbed by bricks can migrate through walls, leading to internal dampness, plaster damage, and mold growth.
- Efflorescence: Dissolved salts within the brick or mortar can be carried to the surface by evaporating water, leaving behind white, powdery deposits.
- Reduced Durability: Cycles of wetting and drying or freezing and thawing can weaken the brick over time, reducing its lifespan.
Managing Porosity and Water Ingress
While bricks are naturally porous, managing water absorption is crucial for the longevity of brickwork. Strategies include:
- Proper design and construction to prevent water exposure (e.g., adequate roof overhangs, damp-proof courses).
- Maintaining mortar joints to prevent water entry through cracks.
- Applying breathable water-repellent treatments in specific situations (though this requires careful consideration to avoid trapping moisture).
In conclusion, bricks are porous by nature due to their composition and manufacturing process. This inherent porosity allows them to absorb moisture, known as water ingress, which is a primary cause of damage like spalling.
