Swimming pools fail in two places. The shell - the concrete tank itself - and the perimeter, where the pool meets the deck, the skimmer, and the surrounding tiling. Both are waterproofing problems. They require completely different solutions.
The shell
A properly built pool shell does not need waterproofing in the conventional sense. It needs a dense, crack-controlled concrete mix and a cementitious slurry that bonds permanently to the substrate. We specify Sika-1 or Mapei Mapelastic systems for most residential pools.
The perimeter
Almost every pool leak we are called to is at the perimeter - the cold joint where the deck meets the coping, the bond between the skimmer and the shell, the penetrations for return lines. These require a flexible polyurethane system, not a cementitious one, because the perimeter moves with thermal cycling.
A word on chemistry
Pool water is not water. It is a mildly acidic, chlorine-loaded chemical solution that attacks every cementitious surface it touches. Your waterproofing has to resist it for decades.
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