The Preslope Under a Mortar Bed
Water finds the top of the liner, not the top of the tile, which is why walk in shower installation lakewood ca nexusphiladelphia treats the preslope as the layer of a Lakewood shower that nobody ever sees and everybody pays for when it turns out to have been skipped.
How a Traditional Pan Works
A sloped mortar bed goes down first. The liner is laid over that slope and clamped into the drain. A second mortar bed goes on top and the tile goes on that. The tile is not the waterproof layer and never was: everything that passes through the grout is meant to run down the liner to the weep holes at the drain.
What Happens Without the First Slope
A liner laid flat on a flat deck makes a tray. Water reaches it, has nowhere to fall, and sits there permanently. The mortar above stays saturated, the room smells, and eventually it appears on the ceiling below. The shower looks entirely normal throughout, which is what makes this the most expensive shortcut in the trade.
Weep Holes Have to Stay Open
The drain body has small openings at the clamping ring so water on the liner can leave. They get blocked by mortar during the second pour unless somebody protects them with gravel or purpose made spacers. A blocked weep hole produces the same standing water as a missing preslope, from a shower that passed every visible check.
Bonded Systems Change the Rule
A modern bonded assembly puts the waterproofing directly under the tile, on top of a preformed sloped foam pan, so there is no second bed and no weep hole. Both approaches are correct. What is never correct is a liner over a flat bed, which is the specific combination worth asking about on any older shower being repaired.
How to Check
Ask for photographs of the sloped bed before the liner went in, and of the flood test afterwards. On an existing shower, standing water in the corners after ten minutes and grout that stays dark for days are the symptoms. Neither proves the fault, but together they justify opening the floor before spending money on new tile.