Case 3

Biological Growth on Parapet Wall

Algae has grown throughout the length of this wall of the roof garden. Algae is grown where moisture is in abundance under the tropical conditions of light intensity. Algae growth is highly governed in these cases by the amount of moisture retained in the substrate, i.e. the retaining wall in this case rather than on the paint surface itself.

This case shows algae all throughout the wall, suggesting that it is possible the whole wall is facing similar conditions of moisture. It is safe to suggest that this has been inherited from the moisture rich soil layers retained by the wall. The turf and its soil substrate can hold considerable amounts of water from plant watering and as storm water collection, leading to high water content being in contact with the concrete elements of the roofing system where vertical damp proofing is inadequate. This contact makes the concrete wall moisture levels go up, bringing in algae growth under the conditions of tropical outdoor environment.