How to Mix Mortar for a Shower Membrane
A shower floor uses a mortar bed, sometimes called dry-pack mortar, to form the slope that the shower membrane lays on. After creating the mortar mix, the tile installer takes into consideration the shower's floor drain placement and the shower floor's size and shape while floating the mortar bed. Most shower floors use a 1/4- to 3/8-inch-per-foot foot slope toward the drain. The shower membrane, a waterproof liner, uses the mortar bed's slope to divert water away from the walls toward the shower's floor drain. Does this Spark an idea?
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Things You'll Need
- 5-gallon bucket
- Coarse-grain sand
- Portland cement
- Wheelbarrow
- Flat shovel
- Water
- Latex additive
Instructions
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1
Combine three 5-gallon buckets of coarse-grain sand and one 47-lb. bag of Portland cement in a wheelbarrow. This mixture makes a mortar mix batch with about a 5-to-1 sand-to-cement ratio and fills a standard-depth 36-by-36-inch shower pan. If floating a larger pan, work the pan with two batches of mortar mix and maintain the 5-to-1 ratio.
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Mix the sand and Portland cement together, using a flat shovel to pull the material from the bottom of the wheelbarrow and place it on top of the mixture. Continue to combine the dry sand and cement, using the bottom-to-top mixing pattern, until the mortar mix has a consistent texture. A bottom-to-top mixing pattern ensures that all of the sand clumps break apart and combine with the cement.
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3
Create a 6- to 12-inch-deep bowl in the top of the dry mortar mix, using the flat shovel to push the mortar.
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4
Pour 1 gallon of either water or latex additive into the mortar mix's bowl. If the bottom of the shower drain rests 3/8 inch or more above the shower pan's membrane, use either water or latex in the mortar mix. If the bottom of the shower drain rests less than 3/8 inch from the top of the shower pan's membrane, use the latex additive in the mortar mix. The latex additive strengthens the mortar mix.
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Pull a shovel full of the dry mortar mix from the bottom of the wheelbarrow and slowly dump it into the water or latex additive. Continue this until the water or latex additive soaks completely into the dry mixture.
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6
Carve out a 6- to 12-inch deep bowl in the wettest portion of the mortar mix, using the shovel to form the depression.
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Place a shovel full of dry mortar mix into the wet mortar mix's bowl. Combine the dry mixture with the wet mixture, using the shovel. Repeat this until all of the mortar mix has a damp, but not wet, consistency.
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Tips & Warnings
When mixed completely, the mortar mix's color changes from a light gray to a dark gray.
