Question
I am creating a raised flower bed  on a concrete patio and i am making a cement mold for the foundation to level out the floor( I have not poured the cement into the mold yet). I will then build a retaining wall for the flower bed out of brick. My question is... how do you create a drain system within a 4" in. concrete mold that will properly drain the flower bed? I do not want the water to drain out the retaining wall brick but to come out the side of the cement slab and into the patio's already created drain hole.

Answer
Hello:

Basically you will need a perforated underdrain pipe placed at the low spot of the planter. Connect the perforated segment of the this pipe to a solid pipe that will connect to the outfall.

Make provision for flooding in the planter by connecting a vertical overflow pipe to the perforated underdrain or by making holes in the side of the planter at the top.


Mark Harshman