Concrete is not waterproof. That surprises people, but a pool shell on its own will let water through — slowly, through the pores and through any hairline crack. What stops it is a waterproofing layer applied to the shell before anything decorative goes on top.
What goes wrong when it is skipped or rushed
Nothing, for a while. That is the difficulty: a pool with poor waterproofing looks identical to a good one on handover day. The signs arrive later.
- Damp patches on the outside of the shell, or on a wall the pool backs onto.
- Tiles or plaster lifting in patches, because water is moving behind them.
- Efflorescence — a white, chalky bloom where water has travelled through concrete and left salts behind.
- A slow, unexplained water loss that no pipe test accounts for.
Why the Gulf is harder on it
Ground conditions here often include salts, and salt-laden groundwater attacks concrete and reinforcement from the outside as much as pool water works on it from the inside. Add a large daily temperature swing, which makes everything expand and contract, and a layer that was applied thinly or over a damp surface has a short life.
What good practice looks like
- The shell is clean, sound and properly cured before anything is applied.
- Corners, floor-to-wall junctions and around every penetration — lights, inlets, the main drain — get extra attention, because that is where movement concentrates.
- The material is applied in the number of coats the manufacturer specifies, in the directions specified, not one thick pass.
- The pool is filled and water-tested before tiling, and left long enough for a slow leak to show.
The question worth asking
Before tiling starts, ask to see the pool held full and the level checked over a few days. It is the one stage that cannot be inspected later without taking the finish off — and a contractor who plans to do it properly will have no reason to mind the question.