Frameless Door: Bottom or Vertical Shower Seals Which First?

Last updated: 2025-11-14

Expert Verified by Laura Liu: 7 Years of Seal Technology Expertise

Confused about which seal to fit first?

This is the #1 reason why shower door corners leak. Get the order wrong, and you'll always have drips!

The Expert Answer is Simple: Always fit the vertical seals first.

Here’s why, and the easy steps to get a perfectly dry corner:

The Golden Rule: Vertical First

The right way: The vertical seal strip needs to overlap and protect the horizontal (bottom) seal.

1. Why Vertical Before Horizontal?

The Principle: We need to completely seal the corner and guide water back inside.

The Problem: If you fit the bottom seal first, the vertical strip creates a gap where they meet.

The Solution: The vertical (side) seal's protruding end must cover and protect the bottom seal's tip. This creates an overlapping, drip-proof barrier.

2. The 4-Step Leak-Proof Plan

Follow this exact order for watertight corners:

Step 1: Install Vertical Seals (Sides)

1. Clean: Glass must be totally clean and dry.

2. Fit: Slot your new vertical seal (Bulb or H-Shape) onto the glass edge.

3. The Overlap Rule (Crucial!): Don't align the vertical seal with the glass bottom. Let it protrude down by 1-3mm into the gap.

💡 Expert Tip: This protrusion is not fixed! It must be just enough to make contact with the T-Shape seal (installed later) and allow the door to close normally, with no visible gaps.

Step 2: Precise Cutting of the Bottom Seal (Horizontal)

• Measure: Mark the length of your bottom seal (with the drip rail) along the door.

• The Key Cut: The bottom seal must be cut short so it can slide into the channel created by the vertical seal's protrusion.

• Note: Only trim the hard PVC part, do not cut the soft fin! (See image for reference).

Step 3: Secondary Defence with a Threshold Seal (MUST READ)

Even a perfect seal can drip under water pressure. The threshold is your last defence.

• Clean & Stick: Clean the floor/tray thoroughly. Apply the self-adhesive T-Shape Seal to create a low-profile dam.

Step 4: Final Check

Close the door. Ensure the vertical seal, horizontal seal, and the T-Shape threshold all make a tight, firm contact. Done!

FAQ

Should horizontal shower seals be fitted before vertical ones?

Definitely not. Always fit the side seal first, trim the bottom seal to fit the overlap, and finish with a T-Shape threshold seal for guaranteed dryness.

3. SIMBA Advantage: Our Solution

When you choose SIMBA, you get:

• Durable Materials: Our seals are independently tested for 30,000 open-close cycles for lasting flexibility (certified for the UK market).

• Pro Guidance: Professional cutting guides are included to ensure your Step 2 cut is perfect.

• Free Expert Help: Contact Laura Liu or our support team anytime for free fitting advice—we guarantee the right fit.

🛒 Stop the Leaks Now! [Shop Our Bottom & T-Shape Threshold Seal Sets]

This article was edited by Laura.