I used a water permeable membrane set against the inner face of a wall that I built(see my photo 100-1740). The reason for this was that the level of soil against this wall on the other side of it was four feet higher than the front face and the water permeable membrane assured complete drainage from top to bottom. Its alot less work than popping holes in a membrane that's not permeable to water and saves alot of guesswork.

Weep holes will work to a certain extent but with concrete beneath the raised bed you will need to ensure there are several at, or just above, ground level or the soil in the bottom of the raised bed will be full of stagnant water.

Hi, welcome to G oY, I think I would be inclined to break up the concrete on the base, before building the raised bed, there is no way you will get rid of all the water with weep holes, and the bottom part of the bed will be permanently soggy, Derek.

I agree with you Derek...