Think I got it. It is too bad the planter is to be right up against the house but no big difference I guess.
It looks like the patio slopes a way from the house. You will want to make sure the planter does too. I don't see that you gain anything with gravel. You do not want to drain the base of the planter over the patio or you are likely to stain it.
It would say put drip irrigation in the planter so as to minimize the amount of water going in at one time. Not much you can do about rain and so forth. You might think about some sort of splash guard behind the planter to keep splattering from the soil on to the wall surface minimized.
How tall will the planter be (not that it makes any difference I guess)? Make sure the planter itself drains well. Might want a layer of gravel in it and extra drain holes?
