Erosion is the gradual wearing away or washing out of material by wind, water, ice, mechanical wear or chemical reactions. In construction this usually means the weathering of façades, natural stone, roof coverings and the soil around foundations. Ignoring erosion eventually leads to cracks, settlement and leaks.
Causes of erosion
| Cause | Effect |
|---|---|
| Rain and driving rain | Washing out of mortar joints, staining of stone |
| Wind-driven dust | Abrasive effect on soft stone |
| Frost-thaw cycles | Frost damage, spalling of brick or concrete |
| Sunlight (UV) | Discolouration, cracking of sealants and plastics |
| Acid rain | Attack on limestone and cement-based materials |
| Mechanical wear | Wear on stair treads and thresholds |
| Root growth | Forcing open joints, cracks in walls |
Erosion of brickwork
In masonry façades erosion usually progresses like this:
- The mortar joint wears first — it is softer than the brick
- Moisture penetrates the brick behind
- Frost causes the brick surface to spall
- The joint becomes deeper and the brick frets
Solution: timely repointing and consider hydrophobic treatment.
Erosion of natural stone
Different stone types vary in vulnerability:
- Limestone, chalk — sensitive to acid rain
- Sandstone — can be eroded grain by grain
- Granite, hard stone — very resistant
- Marble — sensitive to acids and mechanical wear
Erosion of foundations
Soil under the foundation can be washed away:
- Leaking drains — wash sand with them
- High groundwater with flow — undermining
- Poor rainwater drainage — water along the foundation
- Adjacent excavation — loss of lateral support
Consequences: settlement, cracks, sunken paths or patios.
Erosion of roofs
Roof coverings erode under sun, wind and rain:
- Felt/bitumen — dries out, cracks, top layers blister
- EPDM — relatively erosion-resistant but UV-sensitive at seams
- Roof tiles — engobe surface can wear off
- Lead and zinc — form a protective patina
Prevention
- Check and repair pointing in time
- Verify drainage around the foundation
- Hydrophobic treatment for façades
- Clean without aggressive products
- Keep vegetation away from façades
Related terms
- Weathering
- Repointing
- Hydrophobic treatment
- Frost damage
- Carbonation
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