(If you haven't already read the first section of How to Install Tile in Showers, we recommend that you do so.)
After the hot mopped shower pan has cooled down, we filled the shower pan with water up to just below dam height. A measurement was taken (9 5/8") to establish a known point and the pan was left overnight for a recommended water test.
The next day, we checked the area below the new pan for leaks; based on checking the measurement we determined that no water was missing.
The original shower pan installer used a material other that roofing felt that appeared to be more like asphalt impregnated paper. Also the membrane did not extend above dam height by the required 3" minimum. Additionally the membrane was stapled through the top of the dam. These factors all contributed to the shower pan failure.
The next step after draining the pan is to protect the investment with the use of craft type paper or some barrier that will help prevent the penetration of the pan with any tool or object.
Next install a suitable solid backing unless a scratch coat is desired. The solid backing here consists of ½" water resistant gypsum board ("green-board") that is fastened to the studs, appropriately joint taped, and which has one coat of drywall compound on the joints and screw-heads.
We applied 15 pound roofing felt over the drywall from the top of the dam to the ceiling complete with 4" overlapping joints.
Allow the ceiling paper to overlap the wall paper if the ceiling is to be tiled. Make sure the felt overlaps the hot mop at least to dam height.
The 2.5 pound metal lath is installed next with a minimum 2" overlap at seams, is cut at all 90° corners, and is terminated at the intended point of floor mortar height.
Mix wall mortar in the appropriate ratio(s) and begin the mortar installation by "keying" in the mortar fully embedding the wire reinforcing.
Set the back-wall lower float strip in a column of mortar measuring from the front edge of the side-walls.
Use a 3' level of straight edge to properly align and imbed the pre-moistened float strip.
Use a 6' level to establish the position of the upper float strip so that the float strips are plumb and ready to use to float the wall. Fill in the areas between the float strips and use a metal straight or feather edge to cut off the excess mortar. Set the lower side-wall float strips using a framing square to keep the back-wall and side-walls square to one another.
Set the upper float strips with the 6' level in the same manner as that of the back-wall. Fill in the areas between the float strips as described above. Pull the float strips out of the mortar beds prior after filling and fill and smooth the beds. After the mortar beds have cured, the layout begins. In this case the back-wall was a full tile installation. The only layout necessary was to establish the wall center-line and where the ledger boards would be fastened to stack the tile in fresh thin set mortar.
First establish the proper finished height of the shower floor. This measurement should provide a minimum of ¼" of slope per foot of floor. Place a spirit level on the top of the shower drain and make a mark on the back or side-wall where the level is. Next measure up from that mark to provide the proper slope. The bottom of the bottom row of wall tiles should meet this mark. The reason for this method is simple. The installer floats the floor mortar to the bottom edge of the wall tiles automatically establishing the proper slope for the floor.
Use this mark to establish the lower working lines where the ledgers will be fastened. In this case the desire was to have an area below the ledger large enough for a trowel to pass once the lower tile were to be installed after the ledgers were removed. For this tile installation, the distance needed to be two tiles; if placed too low, the fasteners for the ledgers might penetrate the shower pan. The distance was marked off on the back-wall and a spirit level was used to establish the level line. Next the line was transferred to the side-walls in a similar fashion.Next the ledger boards were attached to the back and side-walls with 2" drywall screws.
What's important here is to have straight ledgers and screws that you can easily remove later.
Mix the thin set mortar according to the Manufacturers instructions and "key in" the thin set to the wall with the flat edge of the appropriate sized notched trowel.
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