Concrete with tiles or mosaic

How it is built

The shell is cast or sprayed reinforced concrete designed to retain water. Instarmac's guidance on tiling pools notes that construction is governed by BS 8007, the British code of practice for concrete structures retaining liquids, and that the shell should be confirmed as built correctly and tested for watertightness before tiling starts.

Over the shell, builders often apply a render or screed, then a waterproofing membrane, then tiles fixed with an adhesive rated for permanent immersion, then grout. Construction Chemicals' pool system, for example, uses a membrane applied in two coats to 1.5 mm, a flexible adhesive over the membrane and either a cement-based or an epoxy grout.

Instarmac recommends low absorbency tiles, ideally under 0.5 percent absorption, a full adhesive bed of at least 3 mm without voids, and movement joints planned before tiling, with sealant at least at wall and floor junctions.

Many villa pools use skimmers. Larger pools often use an overflow channel around the edge that drains to a balance tank in the plant room. Ospa, a German balance tank manufacturer, lists connections on its tanks for splash water from the pool, fresh water top-up, emergency overflow and complete drainage, with level electrodes to monitor the water.

Typical problems with age

• Grout washing out or cracking, especially where water chemistry is aggressive.
• Tiles becoming hollow or loose, often where adhesive coverage was incomplete or movement joints are missing.
• Leaks through cracks in the shell, at fittings or through failed waterproofing.
• Cracked coping and surround, particularly in full sun.
• Staining and scale on tiles and in the overflow channel.
• In overflow pools, wear in the grating, the balance tank and its level controls.

What repairs usually involve

Small tile repairs can sometimes be done with the level partly lowered. Larger repairs usually mean removing tiles, repairing the substrate and membrane, re-tiling and re-grouting, then waiting for curing before refilling. Instarmac gives a minimum of three weeks before water is introduced after tiling, with filling no faster than 750 mm in depth per day. The same guidance suggests epoxy grout where aggressive cleaning chemicals are expected.

Leaks are usually located first by a leak detection specialist, then repaired at the fitting, the pipe or the affected section of shell.

UAE notes

Heat and sun affect both the pool and the work. Construction Chemicals specifies application between 10 and 30 °C, out of direct sunlight and not in hot, windy conditions, for its system. Ask how a contractor plans tiling work in summer.

Rooftop and podium pools sit over occupied spaces, so a leak can first show as damp in a ceiling below before the level drop is obvious. In overflow pools, a fault in the balance tank top-up or level control can look like a leak in the pool.

What to tell a specialist about your pool

• Tile type and size: ceramic, porcelain or glass mosaic.
• Skimmer or overflow, and where the balance tank is.
• Age of the pool and of any previous re-tiling or waterproofing.
• Ground level, podium or rooftop, and what lies below.
• Any water loss or damp below or around the pool.
• Drawings, if you have them.