When it comes to sealing up a bathroom, choosing the right product makes all the difference. The best bathroom sealant won’t just stick for a few months: it will seal, bond, and stay mould-free for the long haul, without compromising on aesthetics. So, whether you’re a professional tradesperson or a savvy DIYer tackling shower trays, baths, toilets, or sinks, this post breaks down exactly what to look for – and which products are actually worth your cash.

What Makes The Best Bathroom Sealant?

Not all sealants are created equal. With so many options on the market, it’s become even more important to know exactly what to look for. The best bathroom sealant needs to do more than fill a gap – it needs to be able to withstand sustained daily use. To help you make the right choice, here are some key points to look out for:

Multi-Surface Adhesion

With modern formulas available, your chosen sealant should bond tightly to a vast range of materials, from tiles and acrylic to glass and metals. This is even more vital where two differing materials meet: the best sealant for a shower will adhere securely to both the wall material and the fixture material.

Superior Waterproofing

In a bathroom, constant exposure to moisture and humidity can cause serious issues, from water leaks behind fixtures to black mould growth and weakened bonds. A fully waterproof sealant is essential to form a resilient, watertight barrier that can withstand prolonged humid conditions without peeling or degrading.

Anti-Fungal And Anti-Mould Resistance

Bathroom environments provide ideal conditions for mould growth. In fact, a recent survey found that of those who reported household mould, 68.4% found it in the bathroom. So, to maintain hygiene and prevent unsightly patches, your sealant should have robust anti-fungal and anti-mould properties.

Flexibility

The difference between a good and a great sealant? The latter will handle regular movement and shifting between surfaces without cracking or peeling over time. In bathrooms, surfaces naturally expand and shift due to changes in temperature, humidity, and usage, meaning that if a sealant can’t handle movement, it won’t last, and neither will the job.

Easy Application

Professionals and DIYers alike need fast and reliable results. A quality sealant should help rather than hinder the process. The best sealant will feel smooth and controllable for clean and accurate lines. It should also skin quickly, hitting the right balance between workability and reduced smearing.

Aesthetic Finish

When the job’s sorted, the finish is what everyone sees, so the sealant needs to look as good as it performs. Opt for products that offer non-yellowing options to avoid drawing the eye to all the wrong places. The best bathroom sealants should also be available in a variety of colours to blend seamlessly with the overall bathroom aesthetics, from glossy white to a subtle clear look.

Polymer Sealants Vs Silicone

When it comes to the best bathroom sealant, two commonly used options are polymer and silicone, each having their own strengths. Understanding where and when to use them is the key to getting the best results for your specific project.

Polymer Sealants – Best For Long-Term Bonding And Sealing

Polymer sealants are quickly becoming the preferred option for trade professionals due to their high-performance adhesion, outstanding flexibility, and the ability to cure quickly, even in damp conditions. They’re formulated to form strong, watertight bonds between surfaces, and they actually maintain that bond for longer.

Whilst they might be slightly more expensive than standard silicones, they make up for it in terms of superior long-term adhesion and anti-mould protection. Additionally, they are ideal for finish-sensitive projects due to their versatile paintability.

Overall, polymer options are the best bathroom sealants for the actual job of sealing, especially where durability, adhesion, and water-resistance are critical.

The Place Of Silicone Sealants

That being said, silicone sealants still have their place. A staple in bathroom sealing for decades, they are easy to apply, widely available, and provide a sleek finish.

However, silicone can struggle to maintain adhesion over time, resulting in cracking and peeling. Low-quality silicones, in particular, are also more prone to mould growth and can discolour with age. Plus, if you’re working with natural stone or marble, cheaper acetoxy silicones risk corroding the surface.

Pro Move: The Best Of Both Worlds

If you want a long-lasting and reliable bathroom sealing solution with the crisp lines offered by silicone, the best strategy is to combine both types of sealants. Start by using a polymer sealant to form the core watertight bond between the surfaces and then apply a thin bead of high-grade silicone over the top for a professional-looking finish.

The Best Silicone Option: HB42 Ultimate Silicone

For a silicone product that stands out from the crowd, you can’t go wrong with Ultimate Silicone, which combines professional performance with user-friendly application. The high-gloss, ultra-white finish combined with its non-yellowing formula achieves those attractive, clean lines. Plus, as a non-acetoxy option, you can avoid the harsh and lingering vinegary smell found in lower-quality silicones. You also don’t have to worry about discolouration or damage to materials either: as a neutral-curing option, Ultimate Silicone works well on any surface.

Not to mention, the anti-mould and waterproof qualities of Ultimate Silicone also mean that you’ll be adding another layer of protection when used in combination with your sealant – making it the ultimate professional choice for finish work. See it in action with Roger from Skill Builder.

The 5 Best Bathroom Sealants That’ll Get The Job Done

With the what and why out of the way, it’s time for the star of the show. We’ve picked out five of the best bathroom sealants that tick the boxes for adhesion, flexibility, water-resistance, and finish. So, whatever you’re sealing, pay attention – these are well worth having in your toolkit.

1.      HB42 All-In-One Sealant & Adhesive

Your go-to polymer sealant when you need serious bonding strength, mould resistance, and versatility is the HB42 All-In-One Sealant & Adhesive. It meets the demands of the construction trade, performing reliably in both wet and dry conditions – even underwater. Plus, if you choose the eco-foil alternative, you can reduce waste by up to 95% (and get around 30% more product).

Why We Rate It:

• Bonds almost anything (including lead), in almost any condition
• Odourless and food-safe
• Low emissions with a GEV certification
• Anti-mould, completely paintable
• Available in 7 different colours to suit any bathroom finish
• A true one-tube solution trusted by the trade
• Flexible and skins in only 10 minutes
• Cures in 24 hours, so you can get back to using your bathroom ASAP

2.      Hemway Kitchen & Bathroom All-In-One Polymer Sealant & Adhesive

For a strong all-rounder combining polymer flexibility with acrylic paintability, Hemway’s Kitchen & Bathroom All-In-One Polymer Sealant & Adhesive is a solid choice for sealing and bonding in high-moisture environments. Great mould resistance and ease of application are star features.

Why We Rate It:

• Non-sagging, non-corrosive, and non-staining
• Solvent free, low VOCs, and low odour
• Mould and chemical resistant
• Easy application

3.      Unibond Seal & Bond Sealant Multi-Purpose Adhesive

A popular name in the DIY and trade world, UniBond’s Seal & Bond Multi-Purpose Adhesive offers strong flexibility and water resistance, perfect for both indoor and outdoor uses.

Why We Rate It:

• Fungicidal formulation for bathroom usage
• Adheres to most commonly used construction materials
• Paintable, waterproof, and flexible
• Reliable for general sealing tasks

4.      Geocel The Works Sealant and Adhesive

Geocel’s The Works has become a popular choice for both professionals and DIYers who need a single product that covers multiple applications – including bathrooms. Since it can be painted over with water-based paints, it’s especially handy for those visible areas.

Why We Rate It:

• Limited shrinking or staining during or after curing
• Can be applied directly to wet surfaces
• Flexible enough for joints that see movement
• Odourless and solvent-free

5.      Soudal Fix ALL Flexi

Soudal Fix ALL Flexi offers solid bonding and sealing across a range of applications, from damp interiors to demanding outdoor environments. It’s a dependable all-rounder, especially if you’ve got a few jobs that need seeing to.

Why We Rate It:

• Non-staining on sensitive surfaces
• Strong adhesion without the need for additional primer
• Highly flexible and virtually odourless
• Contains XS1 fungicide for added hygiene in sanitary areas

Final Thoughts

Whether you’re tackling a new installation or replacing old, mouldy lines around your bath or shower, the best bathroom sealant for the job will make all the difference. For the strongest and most reliable seal, modern polymer products (like our Ultimate Sealant & Adhesive) are the clear winners.

Since 2013, HB42 has been developing trade-focussed products that meet the highest professional standards, all whilst being safer for users and kinder to the environment. With a trading legacy spanning six generations, you can be sure that we know what we’re doing.

Ready to get cracking? Explore our comprehensive range of products online or find your local stockist.