I am in the process of installing a new patio and retaining wall. I was hoping that the rain water could drain into the decorative chippings away from the house. The patio is only 6.6m x 2m so I thought that would be enough. I have included a rough illustration and some photos, so hopefully it makes sense.
You are effectively creating a sump or low point directly ouside your patio doors. You have to contend with the run-off from the patio itself, and then, in the winter, you will have run-off *and* groundwater coming from the garden, which is at a higher level.
Unless you have very free-draining ground and a low water table, you could be heading for trouble. I'd want to install some form of drainage around that patio, probably at the foot of the steps, with the patio falling away from the house. Something along these lines...
