Hi wise ones, I'm looking for some drainage advice. We have poured a flat concrete base for a small patio and garden Room. With the addition on the patio tiles the patio comes up higher than the concrete base under the room. The patio is slopes away from the room to a soak away. The room has a wooden base with a DPM cover which continues up the walls. The walls are then cladded. I'm am wondering if we also need an ACO drain or soak away between the patio and room? Any advice very welcome.