natural swimming pond

[Martin Levien]

I began building a natural swimming pond last autumn but ran into problems when I was supplied hydrated lime instead of the hydraulic lime that I had requested. I did not discover this until I had finished the basic structure, base laid plus a skim coat, walls built plus rendered. I am now doing a rescue job on it after the ravages of the winter.  My base is 25cm thick hydrated lime concrete, do I need to waterproof this? How much water will escape from the pond through this base? I have removed about half the lime render from the walls, the rest has bonded well and has gone of hard. If I re-render with the same lime mortar the old and new render should be compatible but will it blow of the brick wall when the damp from the swimming pond penetrates the wall?
                                                           Martin.