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

AvatarByAlison Socha Flooring Materials

Creating a shower pan on a concrete floor is a crucial step in building a durable, watertight shower base that will stand the test of time. Whether you’re renovating an existing bathroom or constructing a new one, understanding how to properly install a shower pan can save you from costly water damage and ensure a smooth, professional finish. The process combines practical skills with attention to detail, making it an essential project for both DIY enthusiasts and professional contractors alike.

At its core, making a shower pan on a concrete floor involves creating a sloped surface that directs water toward the drain, preventing pooling and leaks. This requires careful planning and the right materials to form a waterproof barrier that integrates seamlessly with the surrounding floor. From selecting the appropriate mortar mix to installing waterproof membranes, each step plays a vital role in the overall integrity of the shower base.

Before diving into the hands-on work, it’s important to grasp the fundamentals of shower pan construction and the challenges that come with working on a concrete subfloor. This article will guide you through the essential considerations and techniques, preparing you to tackle the project with confidence and achieve a long-lasting, watertight shower pan.

Preparing the Concrete Floor for the Shower Pan

Before installing the shower pan, the concrete floor must be thoroughly prepared to ensure a durable, watertight base. Begin by cleaning the surface to remove any debris, dust, grease, or loose particles. Use a stiff broom or vacuum followed by a damp mop if necessary. Allow the floor to dry completely before proceeding.

Inspect the concrete for any cracks or uneven areas. Small cracks should be filled with a suitable hydraulic cement or concrete patching compound. Larger cracks or significant unevenness may require grinding or resurfacing to create a flat, stable substrate. A level surface is crucial to ensure proper water drainage toward the shower drain.

If the concrete floor is very smooth or sealed, it may be necessary to roughen the surface using a grinder or acid etch to promote adhesion of the waterproof membrane or mortar bed. Always follow safety precautions when using grinders or chemical etchants.

Installing the Shower Drain Assembly

The shower drain assembly must be securely installed and properly connected to the plumbing before the shower pan is constructed. Ensure the drain flange sits flush with or slightly below the finished floor level to allow the pan mortar to slope correctly.

Steps for drain installation include:

  • Positioning the drain in the desired location and securing it to the plumbing stub-out.
  • Applying plumber’s putty or a rubber gasket under the drain flange to create a watertight seal.
  • Tightening the drain assembly components to prevent leaks.
  • Testing the drain connection for leaks by pouring water into the drain before proceeding.

It is essential to select a drain designed for use with shower pans, preferably one that accommodates a weep hole system beneath the pan mortar to prevent water pooling.

Applying the Waterproofing Membrane

Waterproofing is a critical step to protect the concrete floor and surrounding structures from water damage. There are several types of waterproofing membranes commonly used:

  • Sheet membranes (e.g., PVC, CPE, or rubberized asphalt sheets)
  • Liquid-applied membranes (e.g., polyurethane or elastomeric coatings)
  • Fabric-reinforced membranes

The membrane must cover the entire shower floor area and extend several inches up the walls to create a seamless barrier.

General guidelines for membrane application:

  • Follow manufacturer instructions regarding surface preparation and curing times.
  • Apply primer if required for better adhesion.
  • Overlap seams adequately and seal joints with compatible tape or sealant.
  • Pay special attention to corners, drain openings, and penetrations by using preformed corner patches or extra layers.
  • Allow the membrane to cure completely before placing any mortar or tile.

Building the Mortar Bed for the Shower Pan

The mortar bed provides a sloped surface that directs water toward the drain. Traditional shower pans use a two-layer mortar system consisting of a dry pack or mud bed.

Key points for the mortar bed:

  • Use a mixture of sand and Portland cement, typically in a 4:1 ratio.
  • The mortar should be stiff enough to hold its shape but damp enough to be workable.
  • The bed slope should be a minimum of 1/4 inch per foot toward the drain to ensure proper drainage.
  • Create a “pre-slope” layer first if the waterproof membrane requires it; this layer slopes directly to the drain and supports the membrane.
  • After the membrane cures, apply a “top mortar bed” to form the final slope and support the tile.

Recommended Mortar Mix Ratios

Mortar Layer Sand to Cement Ratio Description Purpose
Pre-slope Mortar 4:1 Dry pack with low water content Provides slope under waterproof membrane
Top Mortar Bed 4:1 Slightly wetter than pre-slope for better workability Supports tile and final slope

Ensuring Proper Drainage and Finishing the Pan

After installing the mortar bed, check the slope by using a level or water test. Water should flow smoothly toward the drain without pooling in any areas. Adjust the mortar bed as necessary while it is still workable.

Once the mortar bed is set and cured (typically 24-48 hours), the shower pan is ready for tile installation or other finishing surfaces. Use a suitable waterproof grout and sealant to maintain the integrity of the pan.

Additional tips for finishing:

  • Protect the shower pan surface during tile installation to avoid damage.
  • Use a bonding agent between the mortar bed and tiles for improved adhesion.
  • Maintain a slight expansion gap around the perimeter to accommodate movement and prevent cracking.

By carefully preparing the concrete floor, installing the drain, applying waterproofing, and constructing a properly sloped mortar bed, you create a reliable and long-lasting shower pan on a concrete floor.

Preparing the Concrete Floor for the Shower Pan

Proper preparation of the concrete floor is essential to ensure a durable, watertight shower pan. Begin by thoroughly cleaning the surface to remove any dust, debris, grease, or loose particles that could compromise adhesion.

  • Inspect for Cracks and Uneven Areas: Examine the concrete slab for any cracks or surface irregularities. Small cracks should be filled with a suitable patching compound, while larger defects may require professional repair.
  • Ensure Proper Drain Placement: Confirm the location of the shower drain and verify that the drain flange is securely embedded in the concrete with adequate waterproofing seals.
  • Confirm Floor Slope: The floor must be sloped correctly toward the drain (typically 1/4 inch per foot) to prevent water pooling. If the concrete floor is flat or slopes away, consider applying a mortar bed to create the proper pitch.
  • Moisture Check: Use a moisture meter to ensure the concrete is dry before proceeding. Excess moisture can interfere with mortar adhesion and waterproofing materials.

Installing the Shower Drain Assembly

The drain assembly is a critical component of the shower pan that must be installed with precision to ensure a watertight seal and proper drainage.

Step Action Key Considerations
1 Set Drain Flange Position the drain flange level with the finished height of the shower pan mortar bed.
2 Apply Waterproofing Sealant Use a high-quality waterproof sealant around the flange to prevent leaks.
3 Secure Drain to Plumbing Tighten connections without overtightening to avoid damage to the flange.
4 Test for Leaks Before proceeding, pour water to verify drainage and check for any leakage.

Constructing the Mortar Bed Base

The mortar bed creates the sloped surface directing water toward the drain. This layer is typically composed of a sand and Portland cement mixture.

  • Mixing the Mortar: Combine 5 parts clean, washed sand with 1 part Portland cement. Add water gradually to achieve a damp, packable consistency.
  • Establishing Slope: Apply the mortar starting at the outer edges of the shower floor, sloping uniformly toward the drain flange at approximately 1/4 inch per foot.
  • Compacting the Mortar: Use a screed or trowel to compact and level the mortar, eliminating voids and ensuring a smooth surface.
  • Drying Time: Allow the mortar bed to cure for at least 24 to 48 hours before proceeding with waterproofing or additional layers.

Applying Waterproofing Membrane Over the Mortar Bed

Waterproofing is crucial to prevent moisture penetration into the concrete slab and surrounding structures.

  • Choose the Right Membrane: Options include liquid-applied membranes, sheet membranes (such as PVC or CPE liners), or fabric-reinforced liquid membranes. Select a product compatible with your shower design and local code requirements.
  • Installation Steps:
    • Clean and dry the cured mortar bed thoroughly.
    • Seal the drain area carefully to ensure continuous waterproofing around the flange.
    • Apply the membrane evenly, extending it up the walls at least 6 inches.
    • For sheet membranes, carefully measure and cut to fit; seal all seams with manufacturer-recommended adhesives or tapes.
  • Curing and Inspection: Allow the membrane to cure as specified. Perform a flood test by plugging the drain and filling the pan with water for 24 hours to confirm the integrity of the waterproofing.

Finishing the Shower Pan Surface

Once waterproofing is complete and verified, the shower pan is ready for the final surface treatment.

  • Secondary Mortar Layer (Optional): Some installations require a thin mortar topping to create a smooth, level surface for tile installation.
  • Tile Backer Board Installation: Secure cement backer board or waterproof tile substrate over the pan surface if necessary, ensuring seams are sealed and waterproofed.
  • Tile Installation: Use a high-quality thinset mortar to install tile, beginning at the drain and working outward, ensuring proper slope is maintained.
  • Grouting and Sealing: Once tiles are set, apply grout and seal all grout lines to protect against moisture intrusion.

Professional Insights on Constructing a Shower Pan on a Concrete Floor

Michael Trent (Certified Waterproofing Specialist, AquaGuard Solutions). When creating a shower pan on a concrete floor, the key is ensuring a proper slope of at least 1/4 inch per foot towards the drain to prevent water pooling. Additionally, using a high-quality waterproof membrane beneath the mortar bed is critical to avoid leaks and potential water damage to the subfloor.

Linda Chavez (Licensed General Contractor, HomeBuild Experts). The preparation phase is essential; thoroughly cleaning and priming the concrete floor before applying any mortar or waterproofing materials ensures optimal adhesion. I also recommend installing a pre-formed shower pan liner or liquid-applied waterproofing to create a seamless barrier that protects against moisture intrusion.

Robert Kim (Architectural Engineer, Structural Innovations Inc.). Structural integrity must not be overlooked when constructing a shower pan on concrete. Reinforcing the mortar bed with wire mesh or fiberglass mesh enhances durability, while carefully integrating the drain assembly with the waterproofing system guarantees long-term performance and prevents costly repairs.

Frequently Asked Questions (FAQs)

What materials are required to make a shower pan on a concrete floor?
You will need a pre-sloped mortar bed or a shower pan liner, waterproof membrane, drain assembly, concrete mix, bonding agent, and tile or finishing materials. Proper tools include a trowel, level, and measuring tape.

How do I ensure proper drainage in a shower pan on a concrete floor?
Create a slope of approximately 1/4 inch per foot towards the drain to prevent water pooling. Use a pre-sloped mortar bed or a custom sloped concrete base to achieve this gradient.

Can I install a shower pan directly on an existing concrete floor?
Yes, provided the concrete floor is clean, level, and structurally sound. Any cracks or imperfections should be repaired before installation to ensure a watertight seal.

What type of waterproofing is recommended for a shower pan on concrete?
A waterproof membrane such as a PVC or CPE liner is standard. Additionally, liquid-applied waterproofing membranes can be used over the mortar bed for enhanced protection.

How long does it take for a shower pan mortar bed to cure before tiling?
Typically, the mortar bed requires 24 to 48 hours to cure sufficiently. However, full curing may take up to 7 days depending on environmental conditions and mortar mix.

Is it necessary to use a bonding agent when applying mortar over concrete?
Yes, a bonding agent promotes adhesion between the existing concrete floor and the new mortar bed, preventing delamination and ensuring durability.
Creating a shower pan on a concrete floor requires careful planning and precise execution to ensure proper drainage and waterproofing. The process typically involves preparing the concrete base, installing a waterproof membrane or liner, building a mortar bed with the correct slope toward the drain, and finally applying the finished surface such as tile or stone. Attention to detail in each step is crucial to prevent leaks and water damage over time.

Key considerations include selecting the right materials, such as a quality waterproof membrane and a well-mixed mortar bed, as well as ensuring the floor slope is consistent and directs water efficiently to the drain. Proper sealing around the drain and edges is essential to maintain the integrity of the shower pan. Additionally, allowing adequate curing time for the mortar bed before proceeding with tile installation helps achieve a durable and long-lasting shower base.

Overall, constructing a shower pan on a concrete floor demands both technical knowledge and craftsmanship. By following industry best practices and adhering to building codes, professionals and DIY enthusiasts can create a reliable, watertight shower pan that provides a solid foundation for a beautiful and functional shower space.

Author Profile

Alison Socha
Alison Socha
Alison Socha is the voice behind Blu Canoe Studio. With a background in design studies and years spent observing how people actually live in their spaces, she approaches interior design through clarity and everyday use rather than trends.

Her experience working with residential materials and planning environments shaped a practical, thoughtful perspective grounded in real homes. Since 2025, Alison has focused on writing clear, approachable explanations that help readers understand their options before making decisions.

Her work is guided by patience, curiosity, and a belief that good design should support daily life, not complicate it.