Questions involving the construction process for waterline tile installation come up often enough so hopefully this should provide some clarification as to the best practices for new pools and remodels alike. This is not meant to replace any product or material manufacturer’s guidelines.
Below is a typical cross section of a pool wall showing the proper placement of a waterproofing membrane:
Tile is used at the waterline of pools as a decorative touch but serves a more important purpose since it can be cleaned of deposits relatively easily and is stable both in and out of water (unlike plaster, quartz and pebble which must remain submerged). The waterline fluctuates greatly during times of use as well as evaporation/refill which makes it important to have a material present that can withstand the Wet/Dry cycles it may encounter without failing.
The pool’s bond beam should be cut square and as straight as possible during the gunite/shotcrete process but slight variations will occur and should be anticipated. A “mortar bed” is typically created to straighten the wall and provide the necessary additional spacing (1/2”-3/4”) for the plaster to be of the appropriate thickness and finishing off flush with the tile. The mortar bed is commonly built up with Type S mortar (3:1 Sand/Portland cement ratio) which like most forms of concrete can present problems down the life of the pool if not properly addressed.
The majority of the forms of concrete, mortar and grout are not waterproof. While the tile itself is not effected by water, the thinset, mortar and gunite/shotcrete do not hold up particularly well when continuously submerged which over time can lead to the tile separating from the shell. To combat this, a cementitious waterproofing agent should be applied after the mortar bed and a thinset rated for continuous submersion should be utilized (most thinsets are only rated for partial water exposure encountered in bathrooms and showers). The thinset should be applied to the mortar bed with a notched trowel and the backside of the tile should be "buttered" with a thin layer of thinset to ensure 100% contact between the tile, thinset and mortar bed and be free or air pockets.
Special care should be taken when choosing a waterproofing agent to be sure that it is compatible with the other materials that are going to be used in the pool. Not all waterproofing agents are compatible with plaster and some can only be applied to the positive or negative side of a spa dam wall, weir wall or trough. Refer to the manufacturer when in doubt on your application.
Lastly the tile joints should be filled with a high quality grout (which also should be rated for submersion). Epoxy grouts are more expensive and require added skill and attention to install but have proven themselves to be a superior product over the standard grout offerings.
Below is a typical cross section of a pool wall showing the proper placement of a waterproofing membrane:
Tile is used at the waterline of pools as a decorative touch but serves a more important purpose since it can be cleaned of deposits relatively easily and is stable both in and out of water (unlike plaster, quartz and pebble which must remain submerged). The waterline fluctuates greatly during times of use as well as evaporation/refill which makes it important to have a material present that can withstand the Wet/Dry cycles it may encounter without failing.
The pool’s bond beam should be cut square and as straight as possible during the gunite/shotcrete process but slight variations will occur and should be anticipated. A “mortar bed” is typically created to straighten the wall and provide the necessary additional spacing (1/2”-3/4”) for the plaster to be of the appropriate thickness and finishing off flush with the tile. The mortar bed is commonly built up with Type S mortar (3:1 Sand/Portland cement ratio) which like most forms of concrete can present problems down the life of the pool if not properly addressed.
The majority of the forms of concrete, mortar and grout are not waterproof. While the tile itself is not effected by water, the thinset, mortar and gunite/shotcrete do not hold up particularly well when continuously submerged which over time can lead to the tile separating from the shell. To combat this, a cementitious waterproofing agent should be applied after the mortar bed and a thinset rated for continuous submersion should be utilized (most thinsets are only rated for partial water exposure encountered in bathrooms and showers). The thinset should be applied to the mortar bed with a notched trowel and the backside of the tile should be "buttered" with a thin layer of thinset to ensure 100% contact between the tile, thinset and mortar bed and be free or air pockets.
Special care should be taken when choosing a waterproofing agent to be sure that it is compatible with the other materials that are going to be used in the pool. Not all waterproofing agents are compatible with plaster and some can only be applied to the positive or negative side of a spa dam wall, weir wall or trough. Refer to the manufacturer when in doubt on your application.
Lastly the tile joints should be filled with a high quality grout (which also should be rated for submersion). Epoxy grouts are more expensive and require added skill and attention to install but have proven themselves to be a superior product over the standard grout offerings.
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