Case 3
- Introduction
- Causes of Defects
- Good Practices
- Standards
- Maintenance and Diagnostics
- Remedial
- Similar Cases
- References
Cause of Defects
Staining of stones may be caused by the natural property of the stone. The natural property of stone to absorb water rapidly coupled with its high porosity causes stone to discolour quickly once it is wet. Areas where frequent washing by rainwater occurs will darken considerably as compared to areas that are sheltered.
Such pattern staining on natural stones is usually due to the temperature difference of the surroundings.
When rain pours, water might be retained in the pores of these stones. With the difference in dampness between the warmer stones and the colder areas surrounding it, the wetting pattern of the stone becomes very distinct.
However, it does not affect the long-term aesthetics of the building since after the granite dries up, the stain-like wetting pattern disappears.
It is usual that the wetting pattern will correspond to the dirt staining pattern after long term exposure of the granite to atmospheric conditions, where atmospheric dust or dirt will adhere more easily to the damp areas.
Staining on a facade has a lot to do with the pattern of rainwater runoff, which in turn is dependent on the facade configuration, colour, texture, as well as the “roughness” and “water absorption” properties of the materials used:
See also Staining of Facades