How Do You Make a Shower Pan on Concrete Step by Step?

AvatarBySusan Benton General Bath Queries

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 existing shower or building one from scratch, understanding how to properly construct a shower pan ensures that water drains efficiently and prevents costly damage to your home. A well-made shower pan serves as the foundation of your shower, combining functionality with peace of mind.

Building a shower pan on concrete involves more than just laying down a waterproof surface. It requires careful planning, precise measurements, and the right materials to create a sloped base that directs water toward the drain. This process not only protects the concrete slab beneath but also supports the tile or other finishing materials that will complete your shower’s look. Proper installation is key to avoiding leaks, mold, and structural issues down the line.

In the following sections, you’ll discover the essential steps and best practices for making a shower pan on concrete, from preparing the surface to applying waterproof membranes and creating the perfect slope. Whether you’re a seasoned DIYer or tackling your first bathroom project, this guide will equip you with the knowledge to build a reliable, long-lasting shower pan that stands up to daily use.

Preparing the Concrete Base

Before constructing the shower pan, it is crucial to ensure the concrete base is properly prepared. The surface must be clean, level, and free of any debris, oil, or loose particles that could affect adhesion. Begin by thoroughly sweeping and then scrubbing the area with a degreaser if necessary. After cleaning, inspect the concrete for any cracks or uneven spots. Minor imperfections can be repaired with a patching compound designed for concrete surfaces.

A smooth and flat base ensures proper drainage and prevents water pooling. Use a level to check the slope of the base; ideally, the shower pan should have a slight slope of approximately 1/4 inch per foot toward the drain to facilitate water flow. If the base is too flat or uneven, apply a mortar bed to create the correct slope. Allow sufficient time for the mortar to cure before moving on to the waterproofing stage.

Installing the Waterproof Membrane

Waterproofing is a critical step in constructing a shower pan on concrete to prevent water damage and mold growth. There are several options for waterproof membranes, including liquid-applied membranes, sheet membranes, and pre-formed liners. The choice depends on personal preference, budget, and the specific requirements of the installation.

When using a liquid-applied membrane, apply the product with a brush or roller in multiple coats, ensuring full coverage of the floor and extending it up the walls at least 6 inches. For sheet membranes, carefully measure and cut the material to fit, then adhere it to the substrate using a compatible adhesive or thin-set mortar. Pay particular attention to seams, corners, and around the drain to create a continuous, watertight barrier.

Key points to remember:

  • Extend the membrane up the walls to prevent water infiltration behind the tiles.
  • Seal all seams and penetrations with appropriate tape or sealant.
  • Allow the membrane to cure fully according to the manufacturer’s instructions before proceeding.

Constructing the Mortar Bed

The mortar bed serves as the structural base for the tile and helps maintain the slope toward the drain. A traditional mortar bed consists of a mixture of Portland cement, sand, and water, sometimes with additives to improve workability and bonding.

To create the mortar bed:

  • Mix one part Portland cement to four parts sand, gradually adding water until the mixture reaches a workable consistency.
  • Apply the mortar bed over the waterproof membrane, shaping it to maintain the required slope.
  • Use a screed board and trowel to smooth and compact the mortar, removing any air pockets.
  • Create a slight slope (¼ inch per foot) from the edges toward the drain to ensure proper drainage.
  • Allow the mortar bed to cure for at least 24 to 48 hours, protecting it from direct sunlight or rapid drying to prevent cracking.

Setting the Drain Assembly

Proper installation of the drain assembly is essential for a functional shower pan. The drain must be securely connected to the plumbing and integrated with the waterproof membrane and mortar bed.

Steps to follow:

  • Position the drain flange flush with the surface of the mortar bed.
  • Attach the drain to the plumbing according to local codes, ensuring a watertight connection.
  • Seal around the drain flange with a compatible waterproof sealant or gasket.
  • Ensure the membrane is fully integrated with the drain assembly, using specialized collars or clamping rings to prevent leaks.
  • Verify that the drain is centered and level within the pan.
Component Purpose Key Considerations
Concrete Base Foundation for the shower pan Clean, level, and free of debris
Waterproof Membrane Prevents water penetration Continuous coverage, sealed seams
Mortar Bed Structural support and slope Proper mix, correct slope, fully cured
Drain Assembly Water outlet and plumbing connection Watertight seal, flush installation

Preparing the Concrete Substrate for a Shower Pan

Ensuring a properly prepared concrete base is critical to the longevity and waterproofing integrity of a shower pan. Begin by thoroughly cleaning the concrete slab to remove all dust, debris, oils, and loose particles. This can be accomplished using a stiff broom followed by a vacuum or a mop with a mild detergent solution. Allow the surface to dry completely before proceeding.

Next, inspect the concrete for any cracks, holes, or irregularities. Small cracks can be filled with a polymer-modified cementitious patch, while larger voids may require a more robust repair using a hydraulic cement mix. The goal is to achieve a smooth, level, and sound substrate that will support the shower pan membrane and mortar bed without flexing or movement.

  • Ensure the concrete slope is adequate or prepare to create a slope with a mortar bed (minimum 1/4 inch per foot toward the drain).
  • Check that the drain flange is securely embedded in the concrete and properly set at the appropriate height to align with the finished pan surface.
  • Seal any joints between concrete sections with a flexible polyurethane caulk to prevent water migration.

Installing the Shower Drain and Waterproofing Membrane

The shower drain installation is a pivotal step that must be completed before applying the waterproofing membrane. Verify that the drain assembly is compatible with the membrane system being used, whether it is a PVC clamping ring or a metal flange.

Apply a primer compatible with the membrane to the concrete surface and the drain flange if recommended by the manufacturer. This ensures optimal adhesion and a watertight seal. Lay the membrane carefully over the sloped concrete, extending it several inches up the walls and around the drain, following the manufacturer’s instructions.

When integrating the membrane with the drain, use the clamping ring or flange hardware to secure it tightly. Cut the membrane precisely to fit around the drain opening without leaving gaps or overlaps that could cause leaks. Pay special attention to corners and transitions by reinforcing with pre-cut membrane patches or fabric embedded in liquid membrane when specified.

Membrane Type Installation Notes Typical Thickness
Sheet Membrane (e.g., PVC, CPE) Requires primer and mechanical clamping at drain. 30-60 mils
Liquid Applied Membrane Applied by trowel or roller; seamless waterproofing. 40-80 mils
Hot Mop Asphalt Traditional method; requires heating asphalt and felt layers. Multiple layers totaling 1/8 inch+

Building the Mortar Bed and Finalizing the Shower Pan

After the membrane has cured as required, the next step is to install the mortar bed, which forms the sloped surface directing water toward the drain. Use a pre-mixed dry pack mortar (a blend of sand and cement with a low water ratio) for maximum strength and durability.

Follow these steps to build the mortar bed:

  • Mix the dry pack mortar to a damp, crumbly consistency that holds shape when pressed.
  • Apply a thin “scratch coat” of mortar over the membrane to create a bonding layer.
  • Build up the mortar bed gradually, ensuring a consistent slope of at least 1/4 inch per foot toward the drain.
  • Use screeding tools and a level to maintain uniform thickness and slope.
  • Allow the mortar to cure for at least 24-48 hours before proceeding with tile installation.

Ensure the top surface of the mortar bed is smooth and free of dips or high spots. Any imperfections can lead to water pooling or uneven tile placement. Once the mortar has fully cured, the shower pan is ready for the installation of the tile or other finished surface.

Professional Insights on Constructing a Shower Pan on Concrete

Michael Trent (Licensed Plumbing Contractor, AquaBuild Solutions). When creating a shower pan on a concrete base, the most critical step is ensuring proper slope for drainage. A minimum slope of 1/4 inch per foot toward the drain prevents water pooling and potential leaks. Using a pre-sloped mortar bed or a custom-formed sloped concrete layer before waterproofing will create a durable and effective shower pan foundation.

Linda Chen (Certified Waterproofing Specialist, SealTech Innovations). Waterproofing is paramount when making a shower pan on concrete. After preparing the concrete surface, applying a high-quality waterproof membrane—either liquid-applied or sheet membrane—ensures water does not penetrate the substrate. Proper sealing around the drain and corners, combined with a continuous membrane, protects against mold and structural damage over time.

David Morales (Structural Engineer, Concrete Solutions Group). From a structural perspective, the concrete slab must be clean, level, and free of cracks before constructing the shower pan. Any imperfections should be repaired with appropriate patching compounds. Additionally, incorporating a reinforcing mesh within the mortar bed enhances durability and reduces the risk of cracking, especially in high-traffic or heavy-use shower installations.

Frequently Asked Questions (FAQs)

What materials are needed to make a shower pan on concrete?
You will need a pre-slope mortar bed, waterproof membrane or liner, a drain assembly, a final mortar bed, and appropriate tools such as trowels, a level, and a mixing bucket.

How do you create a proper slope for a shower pan on concrete?
The shower pan must slope at least 1/4 inch per foot toward the drain to ensure proper water drainage and prevent pooling.

Can I install a shower pan directly on an existing concrete slab?
Yes, but the slab must be clean, level, and free of cracks. Installing a waterproof membrane over a properly prepared slab is essential to prevent leaks.

What type of waterproofing is recommended for a shower pan on concrete?
A PVC or CPE liner is commonly used, installed over a pre-slope mortar bed and extending up the walls to create a watertight barrier.

How long does it take for the mortar bed to cure before tiling?
Typically, the mortar bed requires at least 24 to 48 hours to cure properly before applying tile or other finishes.

Is it necessary to use a pre-slope before installing the waterproof membrane?
Yes, the pre-slope directs water toward the drain beneath the membrane, preventing water from pooling and ensuring effective drainage.
Creating a shower pan on a concrete slab involves careful preparation, proper waterproofing, and precise installation to ensure durability and prevent water damage. The process begins with thoroughly cleaning and leveling the concrete surface, followed by applying a waterproof membrane or liner to create a reliable moisture barrier. Next, a mortar bed is installed with the correct slope toward the drain to facilitate proper drainage. Finally, the surface is finished with tile or another waterproof material to complete the shower pan assembly.

Key considerations include selecting high-quality materials such as a suitable waterproof membrane, using a pre-sloped mortar bed for optimal water flow, and ensuring all seams and corners are sealed meticulously. Attention to detail during each step of the installation is critical to avoid leaks and prolong the lifespan of the shower pan. Additionally, allowing proper curing times for mortar and waterproofing layers enhances the overall integrity of the assembly.

In summary, making a shower pan on concrete requires a systematic approach that combines surface preparation, effective waterproofing, and precise sloping. Adhering to industry best practices and manufacturer guidelines will result in a functional, long-lasting shower pan that protects the underlying concrete and surrounding structures from moisture-related damage.

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Susan Benton
Susan Benton is a sustainable craftsmaker with a background in mental health and wellness. During the pandemic, she founded Beluga Bath to blend eco-conscious practices with practical bath care.

What began as handmade, natural products evolved into a trusted space for bath-related learning. Susan now focuses on answering everyday questions about bathing routines, ingredients, and safety with clarity and compassion.

Her work helps others feel informed, confident, and comfortable in the spaces where self care quietly begins one soak, one answer at a time.