As part of an ongoing refurb of a local Baptist chapel we've been asked to repaint the baptistry which is like a small concrete swimming pool, 4'deep, 5'long and 3'wide. It had previously been painted with a rubberised pool paint and they specced which paint to use. Yesterday it was rubbed down and the first coat applied but when I went back today all the paint on the sides, but not the base or top, had crinkled up. I phoned up the paint supplier and they said it must be damp but the baptistry hasn't had water in it for 2 years however I was then told no damp proof membrane was used when it was cast and half of it is underground. If I had known this I would have used Acrylic pool paint but how do I proceed now? I've got 2/3s of a tin of the expensive rubberised paint and I will be out of pocket if I now have to buy a tin of acrylic.