In this article, you’ll learn how to build a shower pan on a plywood floor step-by-step. From prepping your subfloor to applying a waterproof membrane and installing cement board, this guide will help you create a solid, leak-proof foundation for your shower.
Can you put a shower pan on plywood?
Yes, you can put a shower pan on plywood, but it must be done correctly to ensure proper support, drainage, and long-term durability. A shower pan sits at the base of a shower, collecting water and directing it to the drain. Plywood is a common subfloor material, and when properly prepared, it can provide a strong and stable foundation for both prefabricated and custom-built shower pans.
How to build a shower pan on plywood floor
Gather tools and materials
Before starting, collect everything you’ll need:
- Measuring tape, level, utility knife
- Mortar mix or pre-slope shower pan kit
- Cement board (e.g., HardieBacker)
- Waterproof membrane (liquid or sheet)
- Trowel, screws, waterproof tape, sealant
- Shower drain assembly
Prep the plywood subfloor
Ensure the plywood subfloor is:
- Clean, dry, and free of debris
- Structurally sound (replace any soft or damaged sections)
- Properly secured to floor joists to prevent movement
- Sloped if necessary (for pre-sloped mortar bed pans)
Apply waterproof membrane
Waterproofing is essential to prevent rot and mold. You can choose:
- Liquid Membranes: Roll or brush on multiple coats, allowing each to dry fully.
- Sheet Membranes: Cut to size and adhere to the plywood using thin-set mortar or adhesive, sealing seams with waterproof tape or corner pieces.
Extend the membrane up the walls a few inches for full coverage.
Install and finish cement board
Once the waterproofing layer is dry:
- Install cement board over the plywood and up the walls
- Leave a small gap between boards, and fill seams with alkali-resistant tape and thin-set mortar
- Screw boards into place, following manufacturer spacing guidelines
- Avoid penetrating the shower liner or membrane on the floor
Final tip
For tiled showers, you’ll add a sloped mortar bed over the waterproofing and under the tile. Always check local plumbing codes and manufacturer instructions for best results
What to Know Before Installing a Shower Pan on Plywood
Inspect the plywood subfloor
Before installation, make sure the plywood is structurally sound — free of rot, water damage, or movement. If the subfloor flexes or sags, it can cause leaks or cracks in the shower pan over time.
Use a mortar bed or leveling compound
For most shower pan installations, a layer of mortar is applied between the pan and the plywood. This helps fill any gaps or uneven areas in the subfloor and ensures full contact, support, and leveling.
Waterproofing is critical
Even with a quality shower pan, it’s essential to waterproof the surrounding floor area. This may include applying a waterproof membrane or sealant around the edges where the pan meets the plywood or walls to prevent water intrusion.
Follow manufacturer instructions
Whether you’re installing a tile-ready pan or a pre-formed acrylic model, always follow the specific installation instructions provided by the manufacturer. These usually specify subfloor preparation, types of adhesives or mortars to use, and sealing techniques.
Building a shower pan on a plywood floor requires careful preparation, proper waterproofing, and precise installation of cement board. When done correctly, it creates a sturdy, moisture-resistant foundation that will support your shower for years to come. Whether you're doing a full bathroom remodel or just upgrading your shower area, following these steps ensures your project is safe, durable, and ready for tiling.
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