Renovation guides

How to waterproof a shower yourself: step by step

Draft guide written from standard practice, not yet reviewed by a licensed pro. Follow product labels where they differ.

The one task where a DIY mistake shows up as a repair bill in the apartment below. You waterproof the walls over an existing tub, or over a shower pan that a licensed plumber set and flood-tested. A continuous membrane over the right substrate, sealed corners and curb, and a 24-hour flood test of the pan before any tile touches it.

Difficulty 5 of 5 · 2 weekends · careful

Photo of your room, the look you pick, then this guide with the materials counted for your room.

Step by step

1. Step 1 of 15

   Decide honestly whether this one is yours

   

   Read the stop-gate above. This guide has two DIY paths: waterproofing the walls over an existing tub, or waterproofing the walls and banding onto a shower pan that a licensed plumber set and flood-tested. Setting a new pan and connecting its drain is not a DIY step in this app. If you have never done this, hiring a pro for the pan and membrane and doing the tile yourself is the cheapest version of this project, not the most expensive one. There is no way to inspect this layer once the tile is on.

2. Step 2 of 15

   Buy one manufacturer's complete system

   

   Boards or membrane, seam band, corners, and pipe seals from a single system — and if a plumber is setting a new pan, tell them which system so the pan and drain match it. Print the manufacturer's installation instructions and follow those over anything written here where they disagree.

3. Step 3 of 15

   Strip the shower back to studs and inspect

   

   Everything inside the wet area comes out: old tile, drywall, green board. If you are keeping the tub, cover it with cardboard and tape first. Look hard at the framing and the subfloor for rot, dark staining, or a musty smell. Any of that and you stop — the repair comes before the shower.

4. Step 4 of 15

   Straighten the framing and block the wet walls

   

   Shim or plane the studs until a straightedge lies flat across them — tile shows every hump, and so does the membrane. Add blocking anywhere you will later want a bench or grab bar, because you cannot drill into the finished wall. Frame any niche now, with its bottom sloped slightly forward so water runs out.

5. Step 5 of 15

   Pan and drain: the plumber's part

   

   Replacing the pan or drain: a licensed plumber sets the pan and connects the drain, and it often needs a permit and a pan inspection before tile — check with your city's building department (LADBS in Los Angeles); in an apartment or condo also the HOA. Connecting the drain body to the drain pipe below the floor is plumbing inside the floor, and this app keeps it contractor-only. The drain is connected and set to height before or together with the pan, in a full mortar bed, so the person who sets the pan does both and flood-tests them. Keeping the tub? Check it is solid and does not leak, and move on.

   Pan or tub in place?

   • You are keeping the tub, or the new pan and drain were set and connected by a licensed plumber — not by you
   • New pan: the plumber flood-tested the pan and drain after setting them. Tub: it drains and does not leak
   • Permit and pan inspection handled as your city and HOA require, or no pan or drain was replaced
   • Pan or tub is solid: no rocking, no flex, no hollow spot when you stand on it
   • The pan's drain flange or the tub flange is the kind your membrane system bonds or laps onto

6. Step 6 of 15

   Set the curb

   

   Shower pan only; a tub has no curb, and if the plumber set the curb with the pan, skip this. Cut the curb to length, bed it in the mortar or adhesive the system specifies, and fasten or bond it to the pan exactly as the instructions show. The top of the curb gets a slight slope into the shower.

7. Step 7 of 15

   Hang the wall boards, then stop making holes

   

   Cement board or foam board on every wet wall, gapped slightly off the pan per the instructions, fastened with the specified screws and washers. Over a tub, the board laps over the tub's flange and stops about 1/4" above the tub rim, per the board's instructions. No plastic sheeting behind it. From this point on, no screw, anchor, or nail goes through the wet zone. Where the board meets the drywall outside the wet zone, tape and fill that joint the way the board maker says; it is not part of the waterproofing.

8. Step 8 of 15

   Set the niche, if you want one

   

   Set a preformed niche from the same system into its opening in the board, or line the framed opening with board. Its bottom slopes slightly forward. Band its inside corners and carry the membrane into it like any other wall. Do it now: a niche added after the membrane is a hole in it.

9. Step 9 of 15

   Band every seam and corner first

   

   Bed the fabric band in a layer of liquid membrane over every board seam, every inside and outside corner, the pan-to-wall joint, the curb corners, both sides of the curb, and the niche corners. Over a tub, band the board-to-tub-flange lap as the instructions show. Use the preformed corners where the geometry is three-way. Press the band flat — no wrinkles, no bridging.

10. Step 10 of 15

    Seal the valve and shower-arm penetrations

    

    Slide the preformed pipe seals over the valve body, the shower arm stub, and the tub spout pipe if there is one, and bed them in membrane so the fabric laps onto the wall in every direction. A bead of silicone is not a substitute.

11. Step 11 of 15

    Roll the full membrane to thickness

    

    Two coats is the usual instruction, but thickness is what matters: check the wet film with the gauge against the number on the label and add material where it reads thin. Carry the membrane up the walls to above the shower head, over the curb top and both faces, and out onto the bathroom floor as far as the instructions say. Over a tub, run it down onto the tub flange as the instructions say; the tub-to-tile joint gets silicone later, not grout. Let each coat dry to the label's time.

12. Step 12 of 15

    Cure, then inspect in raking light

    

    Wait the full cure time on the label. Then hold a work light nearly flat against the surface and look for pinholes, thin patches where the substrate color shows through, and any wrinkle in the band. Patch and re-cure anything you find.

    Ready to flood test?

    • Every seam, corner, and change of plane is banded, with no wrinkles or bridging
    • Valve, shower-arm, and tub-spout penetrations are sealed with preformed seals
    • Membrane is continuous from the pan, or from the tub flange, up past the shower head, and over both faces of the curb if there is one
    • Niche, if any, is banded and membraned inside
    • Film thickness matches the label, checked with the gauge
    • No pinholes or thin spots in raking light
    • Full cure time from the label has passed — no fasteners driven since

13. Step 13 of 15

    Plug the drain and fill the pan

    

    Tub instead of a pan? There is no pan to flood; your check is the inspection in the step before and the last step here. Pan: set the test plug in the drain, then fill the pan to at least 2 inches deep, and stay below the lowest point of the curb (or whatever depth your inspector or system asks for). Mark the water line on the wall with a piece of tape so you can see any drop. Tell your downstairs neighbor you are doing this.

14. Step 14 of 15

    Wait 24 hours, then check everything below

    

    Leave the water in for a full 24 hours. Then check the water line against your tape, and go look at the ceiling below, the joists if you can see them, and the floor around the shower for any damp spot. A drop in the line or any dampness means the membrane failed — find it, fix it, and run the test again from zero.

15. Step 15 of 15

    Drain, dry, and release the tile task

    

    Pull the plug, let the pan dry completely, and vacuum out any debris. Lay cardboard in the pan or tub and keep boots and tools off the membrane until the tile goes on. Only now does tile go on.

    Quality check — the flood test gate

    • Pan: water held for a full 24 hours with no drop at the tape line. Tub: the membrane laps onto the tub flange with no gap
    • Ceiling and floor below are dry, checked by eye and by hand
    • No damp spot anywhere around the shower or the curb
    • Membrane still continuous — nothing was drilled or cut during the test
    • Pan or tub is drained, dry, clean, and covered until the tile goes on

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