The Mystery Of The Tile Shower Pan Curb
A tile shower pan curb is the dam that holds back the flood. Especially if a drain briefly stops up, the curb keeps the water in the shower and not all over everywhere.
It's framed up when the shower is framed and is then finished after the second mud layer is on and finished.
The shower pan liner is draped over the curb and carefully sealed at the corners. Corner dam pieces at the corners glued in place are the easiest way to get a perfect seal at the curb edges.
Also note that the shower pan liner should only be fastened to the curb on the outside -- not on the inside.
Reinforced cement mortar is draped over the curb form and the liner membrane to form a curb that doesn't leak and lasts and lasts.
Here's the reinforced part...
Metal lath comes in sheets which are available at tile supply houses or building supply outlets. What you do is bend the metal lath to fit over the top and both sides of the curb.
The lath should fit snug and tight to the pan liner sheet. It should extend to within about an inch of the floor on the inside. It should fit tight with no fasteners.
When the fit is right, attach the lath to the curb form using roofing nails, drywall nails or staples. Use fasteners only outside the curb.
Whatever you do, don't puncture the membrane liner while you're adjusting the lath to fit the curb.
Now for the mud part...
The mortar for the curb is not the same as is used for the floor. It's the same mortar used for brick laying. It contains lime to help it stick and cling. The easiest way to get the right mortar is to obtain pre mixed mortar in sacks. "Pre mixed" means it already has the sand in it. Otherwise, you get masonry mix and add sand yourself.
Here's what you do...
Once the mortar is mixed, apply about an inch of mortar to the top of the curb with a trowel or pointer. Now you'll use that mortar to steady a board, straight-edge, that is the guide for building the front and back of the curb.
Align the straight-edge to where you want the edge of the front of the curb to be. Allow for the thickness of the tile layer. A mud thickness of 3/4 inch is about right, but 1/3 inch should be the minimum.
What you do is to pack mortar into the front of the curb until the entire edge is filled even with the straight-edge. Shape the mortar with the flat trowel.
Now reposition the straight-edge and repeat the mortar application on the other side.
Now slide the board off the top and there you go. The rough curb shape is done.
Just let it harden a bit and then finish shaping the material. Use the straight-edge along with your flat trowel and pointer to scrape and smooth the mortar to just the right shape.
Usually more mortar is added to the top after the curb sides are tiled. That means the curb top can be left rough until the tile is actually set.
The tile shower pan curb is formed over the liner membrane using metal lath for reinforcement and is formed with mortar. The mortar, also called fat mud, is the same mortar mix used to lay brick. It's made from masonry mix and sand, which is readily available pre-mixed.
Read on for the summary of installing a shower pan step-by-step.
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