Waterline Tile Installation - Further Reading

Waterline Tile in Plaster Pools

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.[1]

Below is a typical cross section of a pool wall showing the proper placement of a waterproofing membrane:

Waterline Tile Installation

What is the Purpose of Waterline Tile?

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.

Mortar Bed

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.

Thinset & Waterproofing Agent

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.

Fill Tile Joints with High Quality Epoxy Grout

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.

Under Waterline Tile Repair


Henry 1 Pound Under Water Tile Repair[2][3]

Waterline Tile in Fiberglass Pools

Waterline tile in fiberglass pools is decorative. Some people like the clean look without tile and some people like a decorative tile border.

Materials to Install Waterline Tile on Fiberglass

Materials used to attach the tile to fiberglass include traditional thinset as well as specialized Silicone Tile Adhesive and Silicone Tile Grout for Pool & Spa. Manufacturers include Novagard and Flex-Tile.[4]

If you buy Novagard, verify the date on the bottom of the bottle because you don't want to use old product.[5]

How To Install Waterline Tile on Fiberglass

  • Best to install the tile before the coping but it can be done after[6]
  • Use silicone based adhesive and caulk
  • Drop the water line down to where you want the bottom of the tile to start.[7]
  • Get a wax pencil and make a line around the pool at that level.
  • Drop the water more.
  • Tile up to the underside of your coping leaving a small gap between the top of the tile (cut if necessary) and the coping.
  • Let set.
  • Buy a bunch of scrubbies
  • Apply the silicone grout liberally over the tile.
  • Grout right up to the underside of a cantilevered deck sealing the tile/pool to the deck. That bond with silicone allows for the movement that you get between pool and deck and has remained solid.
  • Get a bucket of warm water and add a little dish soap.
  • Soak a scrubbie in it and use that to smear the silicone into the cracks. The soap repels the silicone and does a great job pushing it into the gaps as well as cleaning the tile and pool surface.
  • When the scrubby gets completely gunked up toss it and get a new one. Takes a bit to get the hang of it but not too much.
  • When you finish let it dry and you are done.

This is a good thread describing the installation of a fiberglass pool and tiles with pictures.