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How to Seal a Bath with a Large Gap | From Gaps to Grace [2024]


Do you need to know how to seal a bath with a large gap? Well, in many homes, there are many gaps around doors and floors. We are planning to write about an important topic that you may need at home soon.

Making sure the water stays where it should be around your bath is important for keeping your bathroom strong and looking good. But when there’s a big gap between your bath and the wall, sealing it up can be a bit tricky. That’s where our helpful guide comes in!

We’ll talk about the problems you might face and give you simple, step-by-step instructions. Whether you love doing it yourself or you’re looking for expert advice, this article is here to help. 

We’ll cover everything from picking the right materials to using smart techniques. Our goal is to make it easy for everyone, so you can fix the common issue of having wide gaps around your bath successfully and make sure it stays that way for a long time. 

Also, if you don’t do this on your own, don’t forget to contact Plumbers Sherman TX, to get some expert help to do this properly. We are based in Sherman, TX.

Why Seal a Bath?

Before delving into the specifics, let’s understand the importance of sealing a bath. Bath sealant not only refreshes the appearance of your bathroom but also serves as a crucial barrier against leaks. The accumulation of water beneath the tub can lead to mold growth, potential health risks, and costly repairs. Additionally, a well-sealed bath enhances the overall aesthetic of your bathroom, providing a clean and polished look.

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How to Seal a Bath Properly

What You’ll Need:

  • Safety gloves
  • Safety glasses
  • Masking tape
  • Safety knife
  • Caulking gun
  • Silicone sealant
  • A silicone applicator or a round-headed tool

Step-by-Step Guide:

Tape the Edges

Begin by using masking tape to mark the area where you’ll apply the sealant. This ensures a neat finish and prevents sealant from spreading onto tiles.

Fill the Bath

Fill the bath with water before applying the sealant. This replicates the weight it will bear during use, preventing cracks in the sealant once the bath is in use.

Prepare the Sealant

Cut the tip of the silicone sealant tube at a 45-degree angle for easy application. Load the sealant into the caulking gun.

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Apply the Sealant

Starting from the furthest corner, apply the sealant in a smooth, continuous motion along the edge of the bath. Consider applying sealant to both the base and the wall if possible.

Smooth the Sealant

Use a sealant applicator, a wet round-ended tool, or your fingertip dipped in soapy water to smooth and shape the sealant edge at an angle. This promotes water shedding back into the bath.

Remove the Tape

Carefully remove the masking tape immediately after smoothing the sealant, leaving a clean edge.

Allow the Sealant to Set

Let the sealant dry for at least 24 hours before using the bath.

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How to Seal a Bath with a Large Gap

If you’re facing a significant gap between your bath and the wall, follow these additional steps:

How to Seal a Bath with a Large Gap

Remove Existing Sealant

If there’s old sealant in the gap, carefully remove it using a utility knife and a flathead screwdriver. Ensure the surface is clean and dry.

Reseat the Bath

Attempt to reposition the bath as close to the wall as possible. This may involve adjusting its position to minimize the gap.

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Apply Two Beads of Sealant

If reseating isn’t possible, apply two separate beads of sealant next to each other—one along the bath’s edge and the other on the wall. Use a wet finger to join the two beads smoothly.

Backer Rod for Larger Gaps

For very large gaps, consider fitting a backer rod into the space before applying sealant on top. This provides additional support and ensures a more effective seal.

Other Sealing Methods

Using Foam

Finely porous foam is a progressive option for sealing large gaps. Ensure the foam is moisture-resistant, and apply it by filling the gap, smoothing, and then cutting and masking.

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Curb Tape

Curb tape, a white polyethylene tape, can be used as an additional decorative coating after filling the gap with foam or cement-sand mortar. It’s easy to use but may have a shorter lifespan.

Cement Mortar

Applying a cement-sand mortar is an economical method, suitable for smaller gaps. Use special supports for larger gaps and follow proper preparation and application steps.

Silicone Sealant

Silicone sealants are ideal for smaller gaps (up to 5 mm). Use sanitary sealants with antibacterial and antifungal additives. Follow precise steps for application and drying.

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How Long Do You Leave Water in Bath After Sealing

After successfully sealing your bath, it’s crucial to exercise patience and allow the sealant to set properly before putting your newly sealed bathtub back into action. Ideally, you should refrain from using the bath for at least 24 hours after the sealing process.

This waiting period is essential to ensure that the sealant has adequate time to dry and adhere effectively. Leaving water in the bath during this curing period is a recommended step. Filling the bath with water adds weight and helps prevent the sealant from cracking when the bath is eventually used.

This step provides a more accurate representation of the sealant’s performance under real-life conditions, especially if the bath is prone to slight movements or settling.

So, while the temptation to enjoy your freshly sealed bath might be strong, exercising patience and allowing the sealant to be fully set will ensure a longer-lasting and more effective seal for your bathtub.

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How to Seal a Bath With a Large Gap

Sealing a bath with a large gap requires a strategic and meticulous approach to ensure a durable and aesthetically pleasing result. If you find yourself confronted with a substantial gap between your bathtub and the wall, as described in the user’s initial query, there are practical steps to address this issue effectively. The first and foremost consideration is the removal of any existing sealant, allowing for a clean slate.

If repositioning the bath to minimize the gap isn’t feasible, a two-bead sealing method can be employed. Apply one bead along the edge of the bath and another on the wall, then skillfully merge the two beads using a wet finger for a seamless finish.

In instances of an exceptionally wide gap, the incorporation of a backer rod before applying the sealant on top can provide additional support and a more comprehensive seal. It’s imperative to use high-quality, mold-resistant sanitary silicone and a reliable mastic gun for this task.

The process involves carefully filling the gap with silicone, smoothing it, and allowing it to dry before applying a second bead for a refined finish. Additionally, considerations like the potential sinking of the bath on wooden floors are addressed by filling the bath with water to counterbalance any weight-induced movements.

The waiting period of at least 24 hours before using the bath ensures the sealant’s optimal curing and guarantees a resilient and effective seal for your bathtub, even in the face of challenging gaps.

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How to Fill the Large Gap Between Bath and Wall

Filling a large gap between a bath and a wall demands a strategic and comprehensive approach to achieve both structural support and an aesthetically pleasing result. When confronted with a substantial gap, particularly when the bath isn’t perfectly aligned with the wall, several effective techniques can be employed.

One approach is to use a backer rod, which acts as a supportive filler before applying sealant. This rod helps bridge the gap, providing a foundation for the sealant to adhere to, ensuring a more durable and secure seal.

Additionally, opting for a high-quality, mold-resistant silicone sealant is crucial for long-term effectiveness. Using a reliable mastic gun, carefully fill the gap with silicone, ensuring thorough coverage.

For an even more refined finish, consider using masking tape to create precise lines and prevent excess sealant from spreading onto adjacent surfaces. Smoothing the sealant with a specialized applicator or a wet finger, especially in a C-motion, helps achieve a polished look while promoting water runoff.

Waiting for the recommended curing time, typically at least 24 hours, is essential before utilizing the bath to allow the sealant to set completely. This meticulous process not only addresses the cosmetic aspect of the gap but also ensures structural integrity, preventing issues such as water seepage and mold growth, thus prolonging the life of the seal.

Filling Large Gaps With Silicone Sealant

Filling large gaps with silicone sealant is a meticulous process that requires attention to detail and the use of quality materials. When dealing with substantial gaps, such as those between a bath and a wall, the first step involves thoroughly cleaning and preparing the surfaces.

It’s crucial to choose a high-quality, mold-resistant sanitary silicone suitable for wet environments. Equipped with a reliable mastic gun, carefully apply the silicone into the gap, ensuring it reaches the depth needed for effective sealing. Utilizing a finger dipped in warm, soapy water facilitates a smoother application and prevents the silicone from sticking.

In cases of uneven gaps, where the width varies along the length, a multi-step approach can be beneficial. After the initial application and drying for a couple of days, create a second smooth bead of silicone using masking tape to establish neat lines. This not only enhances the visual appeal but also contributes to the sealant’s effectiveness.

The use of masking tape during the application process helps maintain precision and prevents excess silicone from spreading onto adjacent surfaces. The final step involves carefully removing the masking tape immediately after smoothing the silicone and allowing it to set overnight.

This patient and methodical approach to filling large gaps with silicone sealant ensures a resilient and aesthetically pleasing seal that addresses both structural and visual aspects, contributing to the longevity and effectiveness of the sealing process.


Sealing a bath with a large gap might seem daunting, but with the right tools and techniques, it becomes a manageable DIY task. Remember to choose the appropriate method based on the size of the gap, bath form, and wall material. Whether you opt for silicone sealant, foam, or cement mortar, the key is meticulous preparation and careful application. Now you can enjoy a beautifully sealed bath, free from leaks and mold, and bask in the satisfaction of a successful DIY project.

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