TLDR

To reseal a bath, remove the old sealant, clean and dry the area, then apply a new flexible, mould-resistant sealant in a smooth line using masking tape for clean edges. Use a ‘pull’ technique, let it cure fully, and reseal every 2–5 years or whenever you see cracks, mould or peeling.

Sealing your bath might not be the flashiest of bathroom projects, but get it wrong and you’ll know about it fast. Leaks, mould, and unsightly cracking are just a few of the problems that can creep in when the seal isn’t watertight, which is why learning how to seal a bath properly is one of the most valuable DIY skills a homeowner can pick up. And the good news is that with the right tools and a bit of patience, it’s a job you can absolutely do yourself. Enter this guide from the team at HB42.

Stick with us – here’s what’s coming up:

• Why A Proper Job Is Worth It
• Signs To Reseal A Bath
• Equipment List
• How To Seal A Bath In 6 Steps
• Bonus Tips
• FAQs
• Conclusion

Why It’s Worth Doing Properly

Sealing the tub does a lot of heavy lifting behind the scenes. A proper seal keeps water exactly where it should be, and keeps it out where it shouldn’t, protecting your walls, floors, and other structures from moisture damage and mould, which has been shown to affect approximately 41% of bathrooms in the UK.

Beyond the functionality of it, though, a neat line of sealant gives your bathroom a polished and professional finish. Done right, it will blend seamlessly into the space. Done badly, it can undermine the look of even the smartest bathroom. So, ultimately, taking the time to do the job properly (and with high-quality products) means better waterproofing, better hygiene, and less maintenance down the line. It’s one of the simplest ways to protect your home.

Signs It’s Time To Reseal A Bath

We’ve covered why you should seal your bath, but when should you do so? Here are a few common signs that it’s time to get out your sealant gun:

• Cracks or gaps in the sealant – Even small splits can let water in and lead to bigger problems down the line.
• Discolouration or yellowing – Over time, sealant can become stained, especially in areas exposed to moisture, sunlight, or cleaning products.
• Peeling or lifting – If the sealant has come away from the surface or looks loose, it’s no longer forming a proper watertight seal.
• Mould or mildew buildup – Black spots or a musty smell around the bath edge usually means the old sealant has lost any anti-fungal properties.
• Visible movement – If your bath moves slightly away from the wall, the sealant is likely to have pulled away or weakened.

If you spot one or more of the above, resealing sooner rather than later can prevent further damage, and leave your bathroom looking much cleaner and fresher too.

Equipment List

Before you start sealing, make sure you’ve got everything to hand. Here’s what you’re likely to need:

• Sealant remover
• Surface cleaner, like the HB42 Solvent Cleaner
• Flexible, high-grip sealant, preferably polymer-based like the HB42 Sealant & Adhesive
• Silicone of choice (such as HB42’s silicone) for finishing
• Caulking/sealant gun
• Masking tape
• Smoothing tool (or your finger)
• Clean cloths
• Gloves
• Utility knife

Picking The Right Sealant Product

When learning how to seal a bath, choosing the right products is just as important as mastering the technique. We’ve covered this in more detail in our post dedicated to the best bathroom sealants, but here’s a quick rundown of what you should keep in mind when making your choice:

(Spoiler alert: you can find all of these features and plenty more in our HB42 Ultimate Sealant & Adhesive range)

Use A Flexible Sealant

Baths and other bathroom structures expand and contract with temperature changes and everyday use. A polymer-based sealant accounts for this, providing excellent flexibility and strong adhesion.

Look For Mould-Resistant Properties

Since bathrooms are humid environments, selecting a product with built-in anti-fungal qualities is key to keeping your seal clean, fresh, and preventing future mould growth.

Choose Sealants Suitable For Damp Surfaces

Sometimes, if time is of the essence, you’ll need to seal a bath when the area is still slightly damp. In these cases, sealants that are specially formulated to bond effectively even on wet surfaces will make your job easier and reduce waiting times.

Consider Eco-Friendly And Low-VOC Options

For health-conscious or environmentally aware DIYers, look for sealants that are low in volatile organic compounds (VOCs), are solvent-free, and produce minimal waste. These options reduce odours and fumes during application, making the process much safer and more pleasant. Additionally, products like our Eco-Foil version of the Ultimate Sealant & Adhesive offer the same high-quality product without the plastic waste.

How To Seal (And Reseal) A Bath Step-By-Step

1.      Remove Old Sealant (If Applicable)

If you’re sealing or resealing a bath, the first (and perhaps most crucial) step is to remove any old sealant. Use a sharp utility knife or a sealant remover tool to carefully cut along the edges of the existing sealant line. Take your time to avoid scratching or causing any damage to the bath surface or adjacent tiles.

Once the bulk of the old sealant has been removed, apply a solvent-based remover designed to soften any stubborn residue. This will help to scrape away the remaining sealant bits and ensure a clean, smooth surface for the new sealant to bond to. Skipping this step or leaving old sealant behind will come back to bite you in the form of poor adhesion and water leaks later on: don’t say we didn’t warn you!

2.      Clean And Dry The Area

After removing the old sealant, it’s essential to prepare the surface thoroughly. Use warm soapy water or a suitable cleaning product to remove soap scum, oils, dirt, and mildew from the bath edges and tiles. Pay particular attention to corners and tight joints where grime tends to build up before rinsing the area well with clean water.

Then, dry the area using a clean, lint-free cloth or paper towels before letting it air dry fully. If your chosen sealant is usable in damp or wet conditions, this step will become substantially faster.

3.      Apply Masking Tape

To achieve a neat, professional-looking seal, it can help to apply masking tape along both sides of the joint where you plan to apply the sealant. This will create crisp, straight edges and prevents excess sealant or silicone bleeding onto the bath surface or tiles.

If applying tape, make sure it is pressed down firmly and of a high enough quality to avoid any product seeping underneath, whilst still being fairly easy to remove.

4.      Load Your Sealant

Prepare your sealant tube by cutting the nozzle tip at a 45-degree angle – the size of the opening will control how much sealant comes out, so cut conservatively to start and adjust as needed.

Place the tube in a sealant gun for better control during application. Hold the gun steady at one consistent angle and apply even pressure to the trigger as you run the dispensed product (known as the bead) along the joint. Aim for a continuous, smooth line without gaps or air bubbles to ensure a watertight seal.

5.      Smooth And Finish

Immediately after applying the sealant bead, smooth it out using a dedicated tool or your wet finger. This process shapes the product into a neat, even line, pressing the sealant firmly into the joint to improve adhesion alongside appearance.

Be sure to wipe away any excess sealant promptly with a damp cloth or paper towel before it starts to set. Finally, remove any masking tape carefully whilst the sealant is still wet. Allow the sealant to cure fully according to the manufacturer’s instructions (usually around 24 hours) before using the bath or exposing the seal to water.

6.      Add A Finishing Bead With Silicone

Once your polymer sealant has cured sufficiently, adding a finishing line of silicone can enhance both the appearance and protection of your bath seal. This step is particularly helpful if you’re looking to achieve that bright, glossy-white finish.

After allowing sufficient time for the first layer to cure fully, use the same careful technique as above and smooth the silicone bead carefully to avoid any lumps or uneven areas.

Extra Tips For A Professional Finish

Mind The Bath’s Expansion And Contraction

Acrylic baths expand slightly when hot water fills them, contracting as they cool. Over time, these micro-movements can crack rigid sealant. To avoid this, ensure that you use a flexible sealant and, if possible, apply it with the bath filled with water to simulate real use.

Practise First

If you’re new to sealing, it can help to take the time to practise beforehand. Grab a scrap tile or even a piece of cardboard to get a feel for pressure and speed. A quick trial run can make the real application much cleaner and more confident.

Try Colour Matching

Most people default to white sealant, but if your bath or tile edges are stone, grey, or even black, a bright white line might stand out awkwardly, especially as the sealant ages. Choose a sealant that closely matches the colour of your tub for a seamless look that enhances the overall finish rather than distracting from it.

This should be fairly straightforward to find since most quality brands will offer different colourways. Our Sealant & Adhesive product, for example, is available in white, grey, anthracite, clear, black, invisible, and brown.

Use A ‘Pull’ Technique, Not Push

When applying the bead, be sure to pull the gun towards you rather than pushing it ahead. The pulling technique gives better visibility and allows you to control flow and pressure much more accurately, especially around corners or bends.

Save And Reuse Your Sealant

If you’re tired of dried-up nozzles or fiddling with caps and nails to reseal your product, there’s something else you can try. After your final application, simply squeeze out a small bit of sealant at the nozzle tip and leave the tube to hang upside down until you need it again. As it dries, that little bead seals the nozzle naturally. When you’re ready to use the sealant again, simply pull off the dried plug, and you’ll find fresh, ready-to-use product underneath.

FAQs

How Often Should I Reseal A Bath?

In general, you should look to reseal your bath every 2 to 5 years, depending on use, ventilation, and the quality of your sealant product. If you notice peeling, mould, or gaps, it’s always better to reseal sooner rather than later so as to avoid any expensive water damage.

Can I Seal A Bath If It’s Slightly Damp?

Yes – but only if you’re using a sealant rated for damp or wet conditions. That said, for the best results and maximum longevity, it’s still recommended to dry the area fully if possible.

What’s The Difference Between Polymer And Silicone Sealants?

Silicone is flexible and easy to apply but can be prone to mould and may not bond well to some surfaces. Polymer-based sealants, on the other hand, offer stronger adhesion, better flexibility, and greater resistance to moisture and movement.

Will This Method Work For Showers And Sinks Too?

Absolutely. The same step-by-step method can generally be used for showers and sinks, or anywhere else you need a waterproof seal. Just be sure to adjust your tools and working angles to suit the shape and size of the space.

Can I Paint Over HB42 Sealants?

Yes! One of the advantages of HB42 polymer-based sealants is that they are completely paintable once cured, making them perfect for finishing touches where the seal needs to blend with painted surfaces. Just take care to ensure that the sealant product has fully dried before applying any paint.

Final Thoughts

And there you have it – how to (re)seal a bath. It might seem like a small job, but when done properly, it makes a big difference to both your bathroom aesthetics and functionality.

With a steady hand, a free afternoon, and the right bathroom sealant product in your corner, you can achieve a clean, watertight finish that lasts for years. Follow the steps, take your time with the details, and don’t cut corners: your bathroom (and future self) will thank you.

Ready to get started? Grab your gear, clear the edge, and lay down that perfect bead.