Moisture

• Moisture is the principle agent of deterioration & is probably also the agent with the greatest influence on the properties of materials .
• In many cases , moisture is a prerequisite for physical , chemical or biological reactions to take place .
• Examples include :

1. Changes in relative humidity can lead to dimensional changes in materials , with deformation , crazing or cracking .
2. Rain , especially when driven by strong winds , can erode &  dissolve certain soft materials 
3. Examples include :
4. When water freezes in the pores of materials such as bricks , stones & concrete , stresses are produced which may cause spalling of the surface .
5. Presence of moisture can promote corrosion of metals , efflorescene & other chemical reactions .
6. Moisture also creates an environement for fungal growth as well as attack by insects in organic materials .
7. Giant hailstones can cause damage to glass surface & roofing tiles .