How Do You Make a Shower Pan on a Concrete Floor?

AvatarByJoseph Thomas Flooring

Creating a durable and watertight shower pan on a concrete floor is a crucial step in any bathroom renovation or new construction project. Whether you’re upgrading an old shower or building one from scratch, understanding how to properly construct a shower pan ensures long-lasting protection against leaks and water damage. A well-made shower pan not only supports the shower base but also directs water safely toward the drain, preserving the integrity of your bathroom for years to come.

Building a shower pan on a concrete floor involves more than just pouring concrete; it requires careful planning, the right materials, and precise techniques to create a waterproof barrier. From selecting the appropriate waterproof membrane to establishing the correct slope for drainage, each element plays a vital role in the pan’s performance. This process can seem daunting at first, but with a clear understanding of the fundamentals, even DIY enthusiasts can achieve professional results.

In the following sections, we will explore the essential considerations and steps involved in making a shower pan on a concrete floor. Whether you’re a seasoned contractor or a homeowner tackling a renovation, this guide will provide you with the knowledge needed to create a reliable, efficient, and code-compliant shower base that stands the test of time.

Preparing the Concrete Floor for the Shower Pan

Before installing a shower pan on a concrete floor, thorough preparation is essential to ensure a watertight, durable installation. Begin by cleaning the concrete surface meticulously to remove dirt, dust, grease, or any loose material. Use a stiff broom or vacuum to clear debris, followed by a degreasing solution if necessary. The concrete must be completely dry before proceeding.

Next, inspect the concrete slab for cracks, holes, or uneven areas. Minor imperfections can be patched using a high-quality hydraulic cement or a concrete patching compound. This will create a smooth, level surface that supports the shower pan evenly and prevents future leaks.

If the concrete floor has a slope or is uneven, apply a self-leveling underlayment. This product flows into low spots and hardens to form a flat base, which is critical for proper drainage in the shower pan. Follow the manufacturer’s instructions for mixing and application, and allow sufficient drying time.

Finally, install a vapor barrier or moisture membrane if required by local building codes or for added protection. This membrane prevents moisture from migrating upward through the concrete and affecting the shower pan materials.

Installing the Shower Drain Assembly

The shower drain assembly is a critical component of the pan installation. Proper placement and sealing of the drain ensure efficient water removal and prevent leaks.

Begin by locating the drain hole in the concrete floor. If a hole does not exist, it must be core-drilled to the size specified by the drain manufacturer, typically 2 to 3 inches in diameter. Verify the drain pipe’s alignment and height before proceeding.

Install the drain flange into the hole, using plumber’s putty or a rubber gasket to create a watertight seal between the flange and concrete. Tighten the flange bolts evenly to avoid warping the seal. Attach the drain body to the flange according to the manufacturer’s instructions.

Test the drain assembly by pouring water into the drain to check for leaks. If any seepage is detected, reseal the flange and verify the connection.

Building the Mortar Bed for the Shower Pan

A traditional shower pan on concrete is often constructed with a mortar bed, which provides a solid, sloped base for the waterproofing membrane and final pan surface.

Mix a dry-pack mortar consisting of one part Portland cement to five parts sand, adding just enough water to achieve a damp, moldable consistency. Avoid overly wet mixes, as they reduce strength and increase shrinkage.

The mortar bed must be sloped toward the drain at a minimum gradient of 1/4 inch per foot. This slope ensures water flows efficiently to the drain and prevents pooling. Use a screed and level to form the slope accurately.

To build the mortar bed:

  • Outline the shower pan area using a form or frame.
  • Start at the drain, creating a slight depression to accommodate the drain flange.
  • Spread the mortar evenly over the concrete floor, working from the drain outward.
  • Use a trowel to shape the slope and smooth the surface.
  • Allow the mortar bed to cure for at least 24 to 48 hours before applying the waterproof membrane.

Applying Waterproofing Membrane

Waterproofing is vital to protect the structural integrity of the shower and surrounding areas. After the mortar bed has fully cured, apply a waterproofing membrane to prevent moisture infiltration.

There are several types of membranes suitable for shower pans on concrete floors:

  • Sheet Membranes: Pre-formed sheets of waterproof material, such as PVC or rubberized asphalt, that are adhered to the mortar bed.
  • Liquid Membranes: Brush- or trowel-applied coatings that cure to form a seamless barrier.
  • Combination Systems: Include both a fabric layer and liquid waterproofing for enhanced protection.

Before application, clean the mortar surface to remove dust. Follow the manufacturer’s instructions for priming or base coats if required. Overlap seams of sheet membranes by at least 2 inches and seal edges tightly around the drain flange.

Comparison of Waterproofing Membrane Types

Membrane Type Advantages Disadvantages Typical Application
Sheet Membrane Consistent thickness, rapid installation, pre-formed Seams require careful sealing, less flexible on uneven surfaces Large, flat mortar beds with minimal irregularities
Liquid Membrane Seamless, conforms to irregular shapes, easy to apply Longer drying time, multiple coats needed Complex shower shapes, retrofit applications
Combination System Enhanced durability, increased puncture resistance More expensive, complex installation High-traffic or commercial showers

Final Steps Before Tiling

Once the waterproofing membrane is in place and fully cured, install the weep holes or drainage channels around the drain to allow water to flow freely beneath the tile layer. Confirm that the membrane slopes uniformly toward the drain to avoid water pooling.

Place a metal lath or wire mesh over the waterproof membrane to reinforce the thin-set mortar bed for the tile installation. This reinforcement reduces cracking and improves bond strength.

Finally, apply the thin-set mortar and install the shower floor tiles according to industry standards. Use appropriate grout and sealants to maintain the waterproof integrity of the shower pan assembly.

Preparing the Concrete Floor for the Shower Pan

Proper preparation of the concrete floor is critical to ensure a durable, waterproof shower pan. Begin by thoroughly cleaning the concrete surface to remove any dust, debris, oils, or loose particles. Use a stiff broom or vacuum followed by a degreasing agent if necessary. The surface must be completely dry before proceeding.

Next, inspect the floor for any cracks, holes, or uneven areas. Fill these imperfections with a suitable concrete patching compound and allow it to cure fully. A level, smooth substrate is essential for forming a consistent slope towards the drain.

Check the floor’s slope: ideally, the concrete should have a slight pitch of approximately 1/4 inch per foot toward the drain location. If the slab is flat or slopes away, you will need to build up a mortar bed or use a pre-sloped shower pan liner system to create the necessary gradient.

Finally, mark the drain location clearly on the floor. Verify that the existing plumbing aligns with this point. If plumbing adjustments are required, complete these before starting the pan construction.

Installing the Shower Drain Assembly

The shower drain is the critical outlet for water and must be installed securely and level. Follow these key steps:

  • Assemble the drain components according to manufacturer instructions. This generally includes the drain body, gasket, flange, and strainer.
  • Insert the drain body into the floor’s drain pipe, ensuring a tight, leak-proof connection using plumber’s putty or silicone sealant as recommended.
  • Position the drain flange so it sits flush with or slightly below the finished surface of the shower pan mortar bed.
  • Temporarily secure the drain in place, verifying that it remains level horizontally in all directions.
  • Test the drain connection by pouring water around the flange to check for leaks before proceeding.

Properly setting the drain at this stage prevents water pooling and infiltration issues later.

Constructing the Mortar Bed for the Shower Pan

The mortar bed serves as the structural base and slope for the shower pan. Use a dry-pack mortar mix, typically a blend of Portland cement, sand, and a water-retentive additive. The consistency should be damp but firm enough to hold shape when packed.

Steps to build the mortar bed:

  1. Create a pre-slope layer
  • Apply a thin layer (about 1 inch) of mortar directly on the concrete floor, sloping downward at approximately 1/4 inch per foot toward the drain.
  • Use a straightedge and level to verify the slope.
  • Allow this layer to cure for 24-48 hours until firm but not fully hardened.
  1. Install the waterproof membrane or liner
  • Lay a PVC or CPE shower pan liner over the pre-slope, extending up the walls at least 6 inches.
  • Secure the liner to the drain assembly with the clamping ring, ensuring a watertight seal.
  • Test for leaks by filling the liner with water and letting it sit for several hours.
  1. Build the top mortar bed
  • After verifying the liner integrity, apply a second mortar layer on top, sloping again toward the drain.
  • This bed should be approximately 1.5 to 2 inches thick and smooth.
  • Ensure the top surface is level at the shower threshold for proper drainage outside the pan.
  • Let the top mortar bed cure fully before tiling or finishing.

Waterproofing and Final Considerations

Waterproofing is essential to prevent moisture damage. Beyond the pan liner, consider these practices:

  • Seal all seams and corners where the liner meets walls with waterproof tape or sealant designed for shower applications.
  • Apply a liquid waterproof membrane over the cured mortar bed if additional protection is desired; allow it to dry thoroughly.
  • Inspect the drain flange connection once more before tile installation.
  • Protect the mortar bed during tile installation to avoid cracks or displacement.
Material Purpose Notes
Dry-pack Mortar Form base and slope of shower pan Mix consistency firm, damp
Shower Pan Liner (PVC/CPE) Waterproof membrane under tile Extend up walls 6″+; seal to drain flange
Plumber’s Putty/Silicone Seal drain assembly connections Use as per manufacturer
Waterproof Tape/Sealant Seal seams and corners Compatible with liner material

Professional Perspectives on Constructing a Shower Pan on a Concrete Floor

Michael Reynolds (Certified Waterproofing Specialist, AquaGuard Solutions). When creating a shower pan on a concrete floor, the critical step is ensuring a proper slope toward the drain, typically a 1/4 inch per foot gradient. This prevents water pooling and potential leaks. Additionally, applying a high-quality waterproof membrane over the concrete before installing the pan is essential to protect the subfloor and surrounding structures from moisture damage.

Linda Chen (Licensed General Contractor, Chen Home Renovations). The foundation of a durable shower pan on concrete involves meticulous preparation of the substrate. I always recommend cleaning and priming the concrete surface before installing a pre-slope mortar bed. Using a polymer-modified mortar mix enhances adhesion and durability. Proper integration of the drain assembly with the waterproofing system is also vital to ensure long-term performance and prevent costly repairs.

Raj Patel (Architectural Engineer, Structural Innovations Inc.). From an engineering perspective, the integrity of a shower pan on a concrete floor depends on both structural soundness and waterproofing. Concrete floors must be inspected for cracks or unevenness prior to installation. Incorporating a bonded waterproof membrane system combined with a well-formed mortar bed ensures that the shower pan will withstand regular use without compromising the building envelope.

Frequently Asked Questions (FAQs)

What materials are needed to make a shower pan on a concrete floor?
You will need a pre-slope mortar bed, a waterproof membrane or liner, a final mortar bed, a drain assembly, and appropriate sealants and waterproofing materials.

How do you ensure proper drainage in a shower pan on a concrete floor?
Create a pre-slope mortar bed that directs water toward the drain at a slope of approximately 1/4 inch per foot, ensuring water flows efficiently without pooling.

Can I install a shower pan directly on an existing concrete floor?
Yes, but the concrete floor must be clean, level, and free of cracks. Any imperfections should be repaired before installing the shower pan system.

What type of waterproof membrane is best for a shower pan on concrete?
A durable, flexible waterproof membrane such as PVC or CPE liners, or liquid-applied waterproofing membranes, are recommended to prevent leaks and protect the concrete.

How long does it take for the mortar beds to cure before tiling?
Typically, the pre-slope and final mortar beds require at least 24 to 48 hours to cure properly before proceeding with waterproofing and tile installation.

Is professional installation necessary for a shower pan on a concrete floor?
While experienced DIYers can install a shower pan, professional installation is recommended to ensure proper waterproofing, slope, and compliance with local building codes.
Creating a shower pan on a concrete floor involves careful planning and precise execution to ensure proper drainage and waterproofing. The process typically begins with preparing the concrete substrate by cleaning and leveling it, followed by installing a waterproof membrane or liner to prevent water infiltration. Next, a mortar bed is applied with a slight slope toward the drain to facilitate efficient water runoff. Finally, the surface is finished with tile or another suitable waterproof material to complete the shower pan assembly.

Key considerations include selecting the right materials, such as a quality waterproof liner and a well-mixed mortar bed, as well as ensuring the slope is consistent—generally a quarter inch per foot toward the drain. Proper installation of the drain assembly is also critical to avoid leaks and maintain long-term durability. Attention to detail during each step helps prevent common issues like water pooling, leaks, and structural damage.

By adhering to industry best practices and local building codes, professionals and DIY enthusiasts can successfully construct a reliable and durable shower pan on a concrete floor. This foundational work not only protects the underlying structure but also contributes to the overall functionality and longevity of the shower installation.

Author Profile

Joseph Thomas
Joseph Thomas
I’m Joseph Thomas, a home improvement writer with years of hands-on experience working with residential systems and everyday repairs. Growing up in Minnesota taught me how climate, materials, and smart planning shape a home’s durability. Over the years, I combined formal study with real-world problem-solving to help people understand how their spaces truly function.

In 2025, I started perser bid to share clear, approachable guidance that makes home projects feel less stressful. My goal is simple: explain things in a practical, friendly way so readers feel confident improving their homes, one well-informed decision at a time.