The picture only shows where water is trapped, not how it could get out (which requires knowledge of grade of the surrounding area.)

Trees raise grade as they grow (due to ever enlarging roots) and the picture shows that might be the likeliest cause of ponding at the patio edge. Previous planting and mulching at the edge could also have contributed, as could have the existence of turf. It raises grade over time as well.

The solution is to lower the grade surrounding the patio and allow the water to drain away (if this is possible) ... or, raise the grade of the patio, such as by installing a new surface over the old one (if this is possible. It depends how grades interface with the house.) Since you intend to install a new surface, that's probably the easiest way to deal with this problem.

Two previous owners laid sod on top of sod and this raised our yard considerably! We are in process of grading down what they added (sod is a couple inches thick), and resurfacing / aka coating the concrete.

Have a few concrete contractors give you bids on roughing up and filling low spots and resurfacing. It's pretty amazing what they can do.

Since drainage is an issue, try to find a landscaper who also does concrete. That way one guy can handle the drainage AND the concrete.

Good luck to you!

Suzi

This post was edited by desertdance on Sun, Apr 6, 14 at 19:02