That Awkward Gap at the End of Your Tub? Here’s How to Fix It

You’ve finished your bathroom remodel, or perhaps you’ve moved into a new home, and there it is: that strange, unusable space at the end of the bathtub. This gap, often a few inches to a foot wide, can be an eyesore and a magnet for dust and moisture. It’s a common issue that arises when a standard-sized tub doesn’t quite fit the dimensions of the alcove.

This space not only disrupts the visual flow of your bathroom but also presents a genuine risk for water damage. Splashes from the shower or bath can easily find their way into this gap, seeping into the subfloor and walls, potentially leading to mold and structural problems. Addressing this issue is not just about aesthetics; it’s about protecting your home’s integrity.

Understanding Why Bathtub Gaps Happen

The gap at the end of a bathtub is a frequent challenge in bathroom design and renovation. It typically occurs when a standard 60-inch alcove tub is installed in a space that is slightly larger. Older homes, in particular, often have non-standard framing dimensions that lead to these awkward leftover spaces.

Another cause can be a shift in layout during a remodel. For instance, removing a linen closet or changing the wall structure can create a larger alcove than intended. Proper planning is crucial, but even with careful measurements, these gaps can appear, leaving homeowners puzzled about the best way to handle them.

The Hidden Dangers of an Unsealed Gap

Beyond the cosmetic annoyance, an unaddressed gap poses significant risks. Water infiltration is the primary concern. Even small amounts of water consistently splashing into this space can lead to severe damage over time. This moisture can compromise the subfloor, leading to issues like a squishy bathtub floor, and weaken the structural support.

Furthermore, the dark, damp environment created by this gap is a perfect breeding ground for mold and mildew. This can impact your home’s air quality and lead to health issues. Properly sealing and utilizing this space is essential for a safe and functional bathroom.

Transforming the Gap: From Problem to Feature

Instead of viewing the space at the end of your tub as a problem, consider it an opportunity. With a bit of creativity and strategic planning, you can transform this awkward gap into a stylish and practical feature. The right solution will not only eliminate the risks associated with the gap but also enhance your bathroom’s overall design and functionality.

From built-in storage to decorative shelving, the options are plentiful. The key is to choose a solution that aligns with your needs, budget, and the existing style of your bathroom. A well-executed solution will look intentional and seamless, as if it were part of the original design.

Solution 1: The Built-In Tiled Shelf or Bench

One of the most popular and effective solutions is to frame and build a tiled shelf or bench in the gap. This creates a continuous, waterproof surface that seamlessly extends from the tub surround. This approach offers both a practical surface for toiletries and a high-end, custom look.

The process involves building a sturdy wooden frame, covering it with cement backer board, and then applying a waterproofing membrane. It’s crucial that this structure is properly waterproofed to prevent any moisture penetration. Once waterproofed, you can tile it to match the rest of your tub surround for a cohesive and integrated appearance.

Solution 2: Custom Cabinetry and Storage

For those needing extra storage, the gap at the end of the tub is a prime location for custom cabinetry. You can have a narrow vertical cabinet built to fit the space perfectly, providing a place for towels, toiletries, and other bathroom essentials. This is an excellent way to maximize storage in a small bathroom.

When opting for cabinetry, ensure the materials are moisture-resistant. Marine-grade plywood or PVC materials are ideal choices for a damp environment like a bathroom. Proper sealing and finishing are essential to protect the wood from humidity and direct water exposure.

Solution 3: Open Shelving for Style and Accessibility

If you prefer a more open and airy look, installing shelves in the gap can be a great option. Floating shelves made from waterproof materials like glass, stone, or properly sealed wood can provide a stylish spot for decorative items, plants, or frequently used bath products. This solution is often more budget-friendly and easier to install than custom cabinetry.

When installing shelves, ensure they are securely mounted to the wall. Consider the weight of the items you plan to place on them. For a bathroom environment, always choose materials that can withstand moisture and humidity to prevent warping or damage over time.

Step-by-Step Guide to Building a Tiled Shelf

Creating a built-in tiled shelf is a project that a moderately skilled DIYer can tackle. It involves framing, waterproofing, and tiling to create a durable and attractive feature. Following the correct steps is crucial to ensure a long-lasting and waterproof result.

Before you begin, gather all your necessary tools and materials. This will include lumber for the frame, cement backer board, waterproofing membrane, thin-set mortar, tiles, grout, and silicone caulk. Careful measurement and planning at the outset will save you time and frustration later on.

Step 1: Framing the Structure

Start by building a simple box frame using 2×4 lumber to fit snugly into the gap. The height of the frame should be level with the top of the bathtub. Secure the frame to the wall studs and the floor to ensure it is stable and robust. If you’re concerned about the overall weight on a second-floor bathroom, using lighter-weight framing materials can be an option, but ensure it’s still structurally sound.

Double-check that the top of the frame is level. You will create a slight slope with the mortar bed later to ensure water drains into the tub. A solid frame is the foundation of a successful built-in shelf.

Step 2: Installing Backer Board and Waterproofing

Cut cement backer board to cover the frame. Secure it to the lumber with appropriate screws designed for cement board. Tape the seams between the boards with fiberglass mesh tape and apply a thin layer of thin-set mortar over the tape. This creates a smooth, stable surface for tiling.

Once the mortar is dry, apply a liquid waterproofing membrane over the entire surface of the backer board, paying close attention to the seams and corners. Apply at least two coats, allowing each coat to dry completely according to the manufacturer’s instructions. This is the most critical step for preventing water damage.

Step 3: Tiling and Grouting

Now you’re ready to tile. Plan your tile layout before you begin applying mortar. Mix your thin-set mortar to a peanut butter consistency and apply it to a small section of the shelf at a time using a notched trowel. Press the tiles firmly into the mortar, using spacers to maintain consistent grout lines.

After the mortar has cured, it’s time to grout. Mix the grout according to the package directions and apply it diagonally across the tiles, pressing it into the joints. After about 15-30 minutes, use a damp sponge to wipe away the excess grout from the tile surfaces. Be careful not to pull the grout out of the joints.

Step 4: Sealing the Joints

The final step is to seal all the corners and the joint where the new shelf meets the bathtub. Use a 100% silicone caulk that is rated for bathrooms and contains a mildewcide. Apply a neat bead of caulk to these areas and smooth it with a wet finger or a caulk-smoothing tool.

Allow the grout and caulk to cure completely before exposing the area to water. This curing time is crucial for the longevity and durability of your new shelf. Once cured, you’ll have a beautiful and functional addition to your bathroom that solves the problem of that awkward gap.

Alternative Quick Fixes for Smaller Gaps

If you have a much smaller gap, a full built-in shelf might be overkill. For gaps that are just an inch or two wide, there are simpler solutions that can effectively seal the space and provide a clean finish. These options are typically less labor-intensive and more budget-friendly.

Even for these smaller gaps, waterproofing remains the top priority. The goal is to create a seamless barrier that prevents any water from getting behind the tub. Choosing the right materials and applying them correctly is key to a successful outcome.

Using PVC Trim and Sealant

For a narrow gap, a piece of PVC trim can be an excellent solution. PVC is completely waterproof and will not rot or warp, making it ideal for a wet environment. You can find PVC trim in various widths and styles to match your bathroom’s decor.

Cut the PVC trim to the length of the tub and secure it in place with a strong, waterproof adhesive. Then, use 100% silicone caulk to seal the joints between the trim and the wall, and the trim and the bathtub. This creates a clean, professional-looking finish that effectively seals the gap.

The Backer Rod and Caulk Method

For very small or irregular gaps, the combination of backer rod and caulk can be a good option. Backer rod is a flexible foam material that you press into the gap to fill most of the space. This provides a solid base for the caulk and prevents you from having to use an excessive amount of sealant.

Choose a backer rod that is slightly larger in diameter than the gap. Press it into the gap so that it sits about 1/8 inch below the surface. Then, apply a thick bead of silicone caulk over the backer rod, ensuring it makes good contact with both the tub and the wall. Smooth the caulk bead for a clean, watertight seal.

Comparing Your Options

Choosing the right solution for the space at the end of your bathtub depends on several factors, including the size of the gap, your budget, your DIY skills, and your storage needs. To help you decide, here is a comparison of the main options:

Solution	Best For	Pros	Cons
Built-In Tiled Shelf	Gaps of 6 inches or more	Durable, waterproof, custom look, adds surface space	More complex, time-consuming, and expensive
Custom Cabinetry	Gaps of 8 inches or more	Adds significant storage, custom fit	Most expensive option, requires professional installation
Open Shelving	Various gap sizes	Adds storage and display space, relatively inexpensive	Less integrated look, items are exposed to moisture
PVC Trim	Gaps under 2 inches	Inexpensive, easy to install, completely waterproof	Only suitable for small gaps, can look like a patch
Backer Rod & Caulk	Gaps under 1 inch	Very inexpensive, good for irregular gaps	Purely functional, offers no aesthetic or storage benefits

Final Considerations for a Flawless Finish

Regardless of the solution you choose, attention to detail is what will set a professional-looking result apart from an amateur one. Always prioritize proper waterproofing techniques to protect your home from moisture damage. Using high-quality materials will ensure that your fix lasts for years to come.

Finally, consider the overall design of your bathroom. The goal is to make your chosen solution look intentional and integrated with the rest of the space. Whether it’s matching tile, coordinating cabinet hardware, or selecting shelves that complement your vanity, these small details will make a big difference in the final outcome. Don’t let that awkward gap detract from your bathroom’s beauty and functionality; turn it into a feature you can be proud of.

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