A number of articles have appeared on French forums concerning pool render finish using “Sika Katymper” and the associated problems with this product. I have worked on one pool with Sika’s product and find it defective. The render needs to be covered with water within 12 to 24hrs (often difficult to achieve), the render is rough (even after sanding) and stains quickly. After less than five years (often sooner), Sika Katymper starts to flake off and disintegrate. Overall, given the number of builders and clients dissatisfied with Sika’s product, I would strongly advise against using it.
Alternatives which I use are pool liners (which today are tougher and more resistant than in the past), and pool resin (Gelcoat or Polyester) which is similar to boat hulls and gives a smooth, hard, waterproof finish to the pool. The advantage of Gelcoat is the ease of application and the pallet of colours available.