One question that many pool owners have pertains to the feasibility of using thin set mortar to glue ceramic tiles to the inside and surrounding areas of pools. Thin set cement mortar is recommended for a superior bond between the base and tiles. However, in it's original state, thin set mortar is not suitable for underwater use. Waterproofing must be done before and after installation of the tiles to prevent damage to the pool and cementing bond.
There are two ways to waterproof the pool base when installing ceramic tiles into a pool. The first way is to lay a protective, waterproof layer under the thin set cement. These are called direct bond waterproofing membranes and can be found at most home supply stores. Often the waterproof coat is applied with a paint brush. Epoxys are a common ingredient of these waterproofing membranes. The second way to apply waterproofing is to mix some waterproof additives with the thin set mortar. The additives gradually seal the pores of the concrete as it dries, which creates a waterproof bond. However, this can also make tiles fall off more easily because the grip on the tile becomes less strong.
Thin Set Gluing
Once the base has been waterproofed, then the thin set mortar can be applied to install the tiles. The area should be completely dry at the time of the application. A dry-set thin set mortar should be used for best performance. The mortar is spread on the waterproofed base and the tiles are pressed into place. Typically it takes several days for the mortar to completely dry. This will vary by manufacturer, but does not usually take longer than 14 days before water can be added to the pool. The lengthy curing process ensures that tiles will not come off due to water or force.
Additional measures are also necessary to completely seal off the water from the thin set mortar. A grout sealer should be applied between the tiles to provide a waterproof cover and sealer. Two kinds of sealer can be used. A grout sealer of latex Portland cement works well for waterproofing the grout. This kind of sealer works in any temperature, and does well going back and forth between wet and dry. An epoxy sealer will also work well at waterproofing but the grout is likely to discolor over time when exposed to UV rays from the sun. However, the epoxy seal is very flexible and durable as well.