Ceramic Tiling A Tub Enclosure - January 13th 2015
The Backing Material
When installing ceramic tiles on the walls above a bathtub, it is very important that the support walls (studs) are sound, with cross-members at the top of the tub and behind the taps to form a solid back-up.
It is very important to have a support "stud" horizontally as well as vertically, where there will be joints in the wall panel material. A properly constructed cement mortar wall is the best back-up possible, but requires special skills and understanding in its formation. Gyproc is a poor material to apply tiles to, in a wet area such as a tub splash, but is still regrettably widely used.
Water resistant gyproc is a slight improvement, but construction panels such as Wonderboard are far superior. As a minimum, in regard to costs, a band of Wonderboard or similar material (not affected by water) should extend about 18 inches up from the top of the tub. This will substantially reduce the potential for bond failure due to water damage.
DO NOT USE PLYWOOD, water can swell and warp this material, leading to cracks in the joints causing deterioration of the life span of the installation.
The Area Between the Tub and Backing Material
Most bathtubs have a lip or flange (about 3/4 inch) that is used to secure the tub to the wall. The normal procedure is to secure the tub, and then start the paneling from the top of this lip, not overlapped to the edge of the tub. If the paneling is overlapped, this causes a slight curvature to the bottom of the wall, which does not look as nice, especially in the corners.
If the gyproc is to be used and is lowered past the top of this lip, moisture problems are likely to occur as gyproc has tendency to absorb or wick water into it, causing swelling and disintegration. When the paneling is stopped at the lip, it should definitely have a horizontal stud behind it to nail to. The gap (approximately 3/4 inch by approximately 3/8 inch) should be filled with a thin - set mortar and smoothed off, extending the wall to the tub.
Planning the Layout
The first step in starting your installation is to use a level on the tub and walls to determine the state of trueness. Starting from the low point on the tub deck, "walk" your tile (using two tiles) from the deck, up about 18 inches and make horizontal level line on all three walls. Next, make a level center line (vertically) on the back wall from the deck to the top row.
Note, the vertical center line may be moved if the tiles end up with small cuts in the corners. Check by laying a row of tiles along the tub, starting from the center line. It does not look professional, if there is a full tile in one corner and a small piece in the other.
Caution should also be taken to allow for walls that are not straight up and down. If the tiles in the corner are to be cut from top to bottom, errors in the straightness of the wall are not as noticeable. If the side walls require cutting of the tiles, it is much nicer if the cuts are in the corners, on the front edge.
Applying the Tiles
Using the correct notched trowel recommended by your tile store for that particular tile, apply the bonding material (thin - set mortar or water resistant mastic) to the back wall. Cover an area two to three rows horizontally at a time and begin applying tiles, starting at the intersection of your two level lines. Be sure you space the tile 1/16 to 1/8 of an inch apart, to allow for grout.
Some bonding materials "skin over" quicker than others, caution should be taken to avoid spreading the bonding material too far ahead of you.
Do not "butt" the tiles in the corners or along the tub, but leave a grout joint width showing, to be filled later with silicone. When you have put the tile onto the glue, twist and tap tiles into place and use a level every few rows, as you proceed up the wall to ensure everything is maintained straight and level.
Once the back wall is in place and the soap dish is placed where desired, start your side wall from outside level horizontal and vertical lines and run your first row to join the back wall. This will ensure the side wall lines up with the back wall, then fill down to deck, cutting out tap holes as close as possible to ensure they can be covered with the cover and sealed later with silicone.
Lastly, repeat the same process on the last wall. Clean down tile with water and allow to dry.
Waterproofing the Corners
Your tile installation at this point should have a 3/16 to 1/8 inch gap up the corners and all around the tub and tile intersection. The gap should be filled with approved anti mildew silicone, to act as an expansion joint. Hot and cold water on the tile surface and vibration, due to outside sources, etc., can cause the grout to crack, resulting in potential water damage.
NOTE: Tub should be full of water when you caulk around the joint between tub and tile.
The expansion material can be applied before or after grouting. Use masking tape to keep the joint sharp. Silicone should not be applied on the top of grout or on top of the surface of the tile.