Case 2

Cause of Defects

Algae growth shows up as a dark discoloration on the roof. It is found most often in warm, humid climates such as the Southeast but does not affect the service life of the roofing material. Algae spores will grow wherever they find minerals, moisture, warmth and light. It does not grow directly on any specific roofing material such as asphalt, concrete or clay tiles, fiberglass or aluminum, but as soon as light accumulation of dust and other organic materials settle on a roof and enough heat, moisture and a little light are available.

Algae, lichen and mosses require damp conditions and a supply of mineral. Often the roof is made their home and they start to grow. In our case here, the moisture come from the water tank. As the concrete beam absorb water, it create the damp condition for algae to grow on. It is unsightly but usually would not cause any serious problem to the roofing system.