5 Golden Rules to Choose the Right Shower Door Seal | SIMBA

Most people spend hours choosing the perfect shower head or tap... but completely overlook one small but crucial detail: the shower door seal

According to the UK Bathroom Fitters Association, 90% of leaking shower enclosures are caused by issues with the bath trim seal.

Yes — we're talking about that almost invisible plastic strip running along the edge of your glass door.

What is that plastic at the bottom of your shower door, really?

We’re SIMBA, a manufacturer with over 20 years of experience in glass seal strips.

Trusted by 514+ global shower brands, we’ve analysed 1,387 real-world leaks and install issues, and boiled it down to 5 golden rules for choosing the right seal strip for bath.

Let’s clear up the confusion — and help you avoid common sealing mistakes!

1. Is the seal strip height at least ≥12.5mm?

 

Here’s the problem:

Some entry-level seal strips on the market measure just 9–10mm in height.

The result?

While this may reduce production costs, it often results in a weaker grip on the glass — especially over time.

We’ve seen cases where seals gradually slide down or lose adhesion after repeated door use.

That’s exactly why some suppliers claim their sealing strips fit “4–6mm glass”, but when you try to install them on 4mm glass, they just won’t stay on.

The height is simply too short to grip the glass securely.

No grip = No seal.

 

The SIMBA Standard:

All our bath sealing strip meet or exceed the 12.5mm grip height, designed to perfectly match international glass thickness standards (4/6/8/10mm).

They hold firm, stay put, and save you from constant replacements down the line.

Plus, every SIMBA glass seal strip is tested to withstand at least 50N of pull force — without slipping off ( Watch our lab-tested grip strength in action )

After grip height, visual clarity is the next key factor — especially if you want your shower enclosure to maintain a clean, modern appearance over time.

 

2. Is the material truly clear and colourless?

Ever noticed that some shower door seals look slightly blue, while others are crystal clear? 

Here’s why.

Most seals on the market are made of PVC — a durable and cost-effective material. But not all PVC is created equal.

Polyvinyl chloride (PVC) was one of the first plastics discovered, and is also one of the most extensively used. It is derived from salt (57%) and oil or gas (43%). It is the world's third-most widely produced synthetic plastic polymer, after polyethylene and polypropylene.

 

Low-grade PVC comes with problems:

• Turns yellow over time from heat and shower products
• Has a bluish haze or foggy look
• Often smells unpleasant

 

High-quality PVC (like SIMBA’s):

• Made from premium, eco-friendly grade PVC ( SIMBA has been verified by SVHC)
• No blue tint, no yellowing, and zero odour
• Up to 90% light transmittance — it blends seamlessly with your glass

 

UV ageing test results:

 

3. Cross-sectional thickness and grip — do the seals actually fit tight?

Many shower door seals on the market don’t wrap tightly enough around the glass. That leads to yellowing, mould growth, and early wear.

Take a look at the comparison below:

🔹 Left: SIMBA’s shower screen seal
🔹 Right: A common alternative on other brand

Sure, the right-hand one may hit the 12.5mm height requirement…

But the cross-sectional thickness and grip fit are nowhere near SIMBA standards. The thickness of the sealing strip must be greater than 1mm.

 

And here's another example we found on YouTube — the pivot shower door bottom seal barely hugs the glass.

That means it’ll slip, sag, or peel off sooner than you expect.

See the difference on our YouTube channel

 

Poor grip = frequent replacements.

We’ve seen this story too many times:

A seal that should last 5–6 years only lasts 7–8 months because of poor fit and weak hold.

And by the time it breaks, the 6-month supplier warranty is just out — forcing you to buy again.

That’s why choosing the right grip size from the beginning makes all the difference.

A well-fitted seal doesn’t just stay in place — it saves time, reduces maintenance, and protects your bathroom investment.

 

4. Is the Soft-to-Hard Fin Connection Strong Enough?

Here’s a critical detail many users overlook:

The junction where the flexible sealing fin joins the rigid U-channel can be a structural weak point — especially in high-use environments like family bathrooms.

Let’s break it down visually:

• The red area represents the soft fin

• The blue area is the rigid U-channel

• The yellow section is the bonding interface

At SIMBA, we’ve engineered this connection with a wider bonding area, reinforcing the soft-to-hard interface for long-term durability.

This structural upgrade helps prevent common issues like fin detachment or leaks, giving your shower a better seal for longer.

 

 

Compared to some seals on the market that use minimal bonding at this junction, our design significantly improves strength and longevity — especially under repeated daily use.

 

Why does this matter?

Most common bath gaskets rely on a narrow glue line or a tiny bonding strip to hold the soft fin in place.

Over time, that connection wears down — causing the fin to split, crack, or detach altogether.

Our upgraded design reinforces this joint, so it doesn’t fail under pressure.

Imagine a family of 5 opening and closing the shower door several times daily.

Without a strong fin-to-frame bond, the strip won’t last even a year.

With SIMBA’s wide-area bonding, you get years of durability — no cracks, no splits.

SIMBA seals are built to take the wear and tear — even in high-traffic bathrooms.

 

5. Does It Fit Curved Glass Doors?

Curved shower screens are one of the most common bathroom designs in the UK. But here's the problem — many people don’t realise how important the curve radius is when choosing a curved shower seal.

 

Understanding the Curvature of Curved Shower Seals The curve of a shower seal is defined by its radius. A quick rule of thumb: Smaller radius = tighter curve Larger radius = flatter curve Think of it like drawing an arc with a compass. An 800mm radius creates a tight curve that hugs the screen perfectly. A 1000mm or 1300mm radius is much flatter — and often just doesn’t fit.

 

 

Why the Radius Matters

A typical 900×900mm curved shower enclosure in the UK needs a seal with a radius around 800mm. If the seal has a larger radius (like 1300mm), it won’t bend enough — which means it springs back, cracks, or even falls off when you open and close the door.

 

What Radius Do Most Suppliers Offer?

We’ve tested it ourselves: most curved seals on the market are made with a 1300mm radius. That’s too flat for most curved screens — and many customers have noticed.

One Trustpilot user wrote:

"I soaked the seal in warm water for 10 minutes, but it still wouldn't bend to fit my curved shower screen. It just cracked. Total waste of money."

SIMBA’s Solution

At SIMBA, we use advanced flexible materials and precision molds to create seals that can curve down to a true 800mm radius — no cracking, no springing back.

As one customer, Emma, shared:

“Since switching to SIMBA’s curved seals, I no longer worry about leaks or spring-back. Installation was smooth, and the quality is truly reliable.”

 

 

Brand Certification & After-Sales Service

Shower door seals are products that often require DIY installation.

But since not everyone is an expert, having timely support is crucial.

Quick responses and easy-to-find contact details are key factors when choosing the right seal.

A high-quality seal isn’t just about looking good — it’s about lasting performance:

 

Third-Party Authoritative Certifications:

• ISO 9001 (Quality Management System)— internationally recognised certificate proving our products meet high quality standards
  View SIMBA‘s Certificate

• ISO 14001 (Environmental Management System) — certified commitment to environmentally friendly production
  View SIMBA‘s Certificate

• SVHC Non-Toxic Certification (EU REACH Environmental Standard) — guarantees materials are free from harmful chemicals and safe for you and the environment
  View SIMBA‘s Certificate

We also follow a strict quality testing process — see our reports here

 

After-Sales Guarantee:

• 90-minute fast response time, WhatsApp direct contact with our manufacturing technicians

• Send a video of the issue → replacement parts shipped within 48 hours

• Email support: info@showerdoorseal.uk

Choosing SIMBA for your shower door seals means turning “small transparent problems” into “clear big advantages.”

 

Quality Comparison

Criteria	✅ Quality Performance (SIMBA)	⚠️ Common Issues with Low-Quality Products
Height	≥12.5mm for a firm grip and stable installation	Too short, only 9-10mm, prone to loosening and falling
Transparency	Nearly glass-clear, no blue or yellow tint, visually seamless	Blueish, yellowing, hardening, affects appearance
Installation	Comes with direction arrows, diagrams, and installation videos	No installation guidance, easy to install incorrectly
Curvature Fit	Supports small radius curves down to 800mm, perfect for curved glass	Radius about 1300mm, cannot bend properly, prone to rebound and cracking
Certifications & After-sales	Certified ISO 9001, ISO 14001, SVHC; fast response and technical support	No certifications, no after-sales service

 

 

Frequently Asked Questions (FAQ)

 

Q1: My glass door is 10mm thick. Which seal strip model should I use?
A: We recommend choosing a model with a gripping width ≥12.5mm, specifically designed for 10mm glass. Send us a photo, and we’ll help you pick the right one.

 

Q2: How often do I need to replace the seal strip?
A: SIMBA seal strips typically last 3-5 years, depending on usage frequency and cleaning methods.

 

Q3: Are these suitable for curved doors or magnetic doors?
A: Yes. SIMBA offers various special models including curved and magnetic seal strips, all customizable.

 

 

Conclusion

Whether you’re replacing a single strip or managing a bulk project, SIMBA is here to help.

Not sure about the gap size or glass thickness? Send us a photo — our experts will recommend the best fit.

Need custom or curved seal strips? We’ve got solutions ready for you.

Want to ensure compliance and durability? Our seals are fully certified and tested.

Reach out today — and let’s make sure your next shower seal is the last one you’ll need for years.