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How to Design A Custom Concrete Shower Pan

Pour a perfect base for the power-shower.

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Step 1: Prepare the Shower Area

Make sure the subfloor under the new shower is clean, dry and in good condition before getting started. A professional plumber roughed in the shower drain before Amy and the homeowners got started.

A rubber membrane lines the bottom of the shower area as another line of protection against leakage. Remove the drain and drain flange and set aside, then spread out the membrane over the shower area. Center the membrane so that it extends 10" to 12" up the wall studs.

Note: Amy recommends taking off shoes before working on the membrane to prevent accidental tears.

Step 2: Secure the Membrane

Flatten the membrane against the bottom of the space, then smooth it up the studs and nail to the studs with large-head nails such as roofing nails. Amy nailed the membrane 6" to 8" up; check local building codes for details on where to nail the membrane and what grade of membrane to use.

Fold the membrane over at the corners -- like making hospital corners with a bedsheet -- to get a clean edge. Nail to the stud through all layers.

Step 3: Secure the Drain Plate

With the membrane secured, use a utility knife to carefully cut out the drain hole. Don't cut the hole too large; if there's a grout leak or other water leakage, the membrane needs to be able to funnel the water right down the drain. Put the drain plate in place and tighten the bolts with a socket wrench.

Cover the top of the drain with painter's tape to protect it and screw it into the drain, leaving a 1-1/4" gap between the drain and the drain plate.

Step 4: Mark the Final Concrete Height

Use a level to mark a line all the way around the rubber membrane to show the final height of the concrete. For this project, the concrete came up 2-1/2" at the wall, sloping down to 1-1/4" at the drain. Check local building codes for specific requirements.

Step 5: Build a Curb

To build a curb at the shower door, measure and cut a piece of 2x6 lumber to fit across the outside of the shower door studs. Screw the piece to the studs at floor level. Flatten the rubber membrane against the 2x6 and trim off the excess with a utility knife.

Step 6: Position the Door Studs

Measure and cut a piece of 2x4 lumber to fit across the inside of the shower door studs. Position it inside the door studs so that the top of the 2x4 is level with the top of the 2x6 and screw into place.

Step 7: Prepare and Pour the Concrete

Wearing safety glasses and a dust mask, mix concrete according to the manufacturer's instructions until it's the consistency of a milkshake. Use a drill with a whip bit to mix the concrete quickly and evenly.

Pour concrete onto the rubber membrane and spread it out with a mason's trowel. Spread the concrete evenly, working it up to the marked line and sloping it down to the drain. Gently bat the surface of the wet concrete with the flat side of the trowel; this will bring moisture to the surface and help the concrete dry to a smoother finish. Don't forget to fill the curb form with concrete as well. Let the concrete dry completely before tiling.

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Renovate your home with host Amy Matthews.

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