A shower door seal (or shower screen seal) is a strip of flexible material—usually silicone, PVC or similar polymer— affixed to the edge of a glass shower panel or door to prevent water from leaking out. Without proper sealing, your bathroom floor can end up wet, SIMBA shower door seal slippery, and subject to water damage, mold growth, and more.
But not all seals are created equal. Depending on where they sit (bottom, side) and how they function (magnetic or plain contact), seals perform different roles and have different design constraints. This article breaks down the differences between bottom seals, side (vertical) seals, and magnetic seals, and helps you pick the right type for your shower setup.
Bottom Seal
Definition & Purpose
A bottom seal sits along the lower edge (threshold) of a shower door or screen. Its main job is to intercept water that might run down the glass and prevent it from spilling outside the enclosure.
Typical Features
Usually a strip or fin-like lip that presses against the shower base or threshold (floor or tray)
May have a “drip rail” design: a wavy or angled profile so water drips back inside rather than flowing out
Often made slightly flexible so it can adapt to small irregularities in the surface
May be replaceable (snap-on, press-fit) or adhesive-backed
Where It’s Used
Sliding shower doors (inner bottom edge)
Pivoting or hinged doors (bottom of the moving door)
Fixed panels to help protect the joint between glass and the base
Advantages & Limitations
Advantage: It handles gravity-driven leaks — even if side seals are perfect, water still travels downward, so bottom seals are crucial.
Limitation: It can wear out faster (abrade against base), accumulate soap scum, or suffer damage if the base is uneven.
Side (Vertical) Seal
Definition & Purpose
A side seal (also called a vertical or lateral seal) is installed along the vertical edges of shower doors or panels—typically where two doors meet (in bi-fold or sliding systems), or where the door meets a fixed panel or frame. Its job is to block water splashing sideways out of the enclosure.
Typical Features
A vertical strip profile, often H-shaped, L-shaped, or U-shaped
May clamp over the glass edge or insert into a channel
Some side seals include fins or lips that press against adjacent glass or frame
Flexible to accommodate small movements or misalignments
Where It’s Used
Between two sliding doors (the meeting edge)
Between a hinged door and a fixed panel
On the side edges of sliding panels
Advantages & Limitations
Advantage: Prevents water from escaping laterally (critical in corner or alcove installations).
Limitation: If not perfectly aligned, gaps may form. Also, side seals alone can’t handle water that travels down — unless the bottom edge is also sealed, leakage may occur.
Magnetic Seal
Definition & Purpose
A magnetic seal is a special type of seal that incorporates magnets—generally embedded in two mating edges of a door or panel—to ensure a tight, self-closing and self-sealing interface. It’s often used in frameless glass showers so that two doors (or a door and fixed panel) latch together securely.
Typical Features
Magnet strips are embedded within clear or translucent plastic/silicone extrusion
As the two edges approach, magnets attract to “snap” together
Creates a tight seal that resists water leakage along that joint
Helps “pull” the door edges to close flush
Where It’s Used
Frameless shower door systems where two doors meet
Pivoting/hinged doors where you want confident sealing without reliance on perfect alignment
Doors that open/close repeatedly and need consistent sealing performance
Advantages & Limitations
Advantage: Self-aligning and self-closing effect; tight seal reduces leakage along the edge.
Limitation: Costlier than plain seals; magnet strength must be balanced (too weak = loose seal, too strong = difficulty closing). Also, over time, magnet or seal integrity could degrade, especially with scale buildup.
Comparative Table
Feature Bottom Seal Side (Vertical) Seal Magnetic Seal
Position Lower edge / threshold Vertical edges Where two door edges meet Primary job Stop downward leaks Block lateral / splashing leaks Ensure tight mate and seal along door junction Extra function May include drip profile May include fins/lips Magnet “snap” + seal
Common materials Silicone, PVC, flexible plastics Similar to bottom seals Plastic/silicone with embedded magnet strip Strengths Handles gravity drip Handles side leakage Self-closing alignment, tight contact Weaknesses Wear from contact, uneven base Gaps if misaligned Higher cost, magnet aging, scale interference
How to Choose the Right Seal (or Combination)
In real-world shower installations, you almost always need a combination of seal types. Below are tips to guide your selection:
1. Know your door configuration
Frameless dual doors? You’ll likely want magnetic seals on the meeting edges + bottom seals on each door.
Sliding doors? Bottom seals plus side vertical seals where doors overlap.
Hinged door plus fixed panel? Vertical seals between glass and panel, bottom seal to prevent leak under door.
2. Match glass thickness: & gap tolerances
Seals are designed for particular glass thicknesses (e.g. 4 mm, 6 mm, 8 mm). Using mismatch can cause poor fit. (As seen on Simba, they categorize by thickness.)
Also measure the gap you want to seal (e.g. 3–18 mm, 11 mm, etc.). Simba shows “gap” ranges in their product listings.
3. Material & flexibility
Softer seals conform better, but may wear faster. Stiffer ones last longer but may have leakage if surfaces aren’t perfectly smooth.
4. Ease of replacement
It’s smart to choose seals that can be removed/changed without replacing the entire door.
5. Maintainability
Magnets can attract mineral buildup; bottom seals near the tray may get scum – ease of cleaning matters.
6. Edge priority
Always ensure side seals are aligned before installing bottom seals, since if side leakage overwhelms, bottom seals will struggle to compensate.
Installation & Maintenance Tips
Ensure smooth mating surfaces — clean and dry surfaces before attaching seals.
Cut precisely — avoid gaps at corners.
Use correct orientation — some seals have a preferred “facing” side.
Check alignment under different positions — ensure seals don’t twist or lift when the door opens.
Clean regularly — soap scum or scale buildup will degrade the seal’s effectiveness (especially magnetic surfaces).
Replace when worn — even high-quality seals eventually degrade or lose their tightness.
Summary
A bottom seal blocks water traveling downward and is installed at the lower edge of a shower enclosure.
A side (vertical) seal is placed on the lateral edges to prevent water splashing out sideways.
A magnetic seal adds magnetic attraction to provide a self-sealing effect between two meeting edges, usually in frameless designs.
Each has its role, and often you’ll need more than one in a shower design. Choosing the right combination—matched to your door type, gap, glass thickness, and maintenance habits—ensures a leak-free, long-lasting, and user-friendly enclosure.
