The use of drain cell mats will be similar to the use of planter stands in terrace and container gardening: : Drain cells lift the pots/grow-bags and create a gap between the floor and grow bag. They prevent all-time wet conditions on the areas where grow bags are placed, on neglecting which may result in damaging of the roof. They facilitate the free flow of water underneath them. This also prevents algae or unwanted pathogenic and insect growth under/near to grow bags and pots. Eliminates the use of gravel course in roof gardening: Creates proper drainage base when used in creating a roof garden. Drainage cells create better drainage than gravel ones. Relieves hydrostatic pressure on retaining walls: Without the drain cells, water always stands on the floor by which the roof may damage, and rainwater/excess water from growing media percolate into the roof. This water creates hydrostatic pressure on retaining walls by which deflection/cracks may appear on them. But by using drain cells, water drains down to the waterproof layer and enters the sewage system very soon by which the damage to the roof and retaining walls can be prevented.