Mirror Guide · 2025

Read time: ~6 minutes · Updated: 23 Sep 2025

Choosing the right mirror thickness is important for durability, look, and safety.
Whether it’s for your bathroom, wall décor, or gym installation, picking between 4 mm, 6 mm or 8 mm can make a difference.
This mirror thickness guide helps you understand what each thickness offers — and which one suits your project best.

Mirror types & applications

Mirrors come in various thicknesses, each suited for different uses: bathroom vanity mirrors, wall-decor pieces, or large gym wall installations. The thickness you choose affects weight, durability, edge finish, safety, and cost.

4 mm mirrors

• Lightweight and easy to install for small or decorative mirrors.
• Less expensive, suitable where mirror edges are supported by frames.
• More likely to flex or chip if exposed edges are unprotected.
• Best used in bathroom cabinets, small decorative wall mirrors, or vanity surrounds.

6 mm mirrors

• The standard domestic mirror thickness for many wall-mount settings.
• Better rigidity; balanced weight vs cost.
• Exposed edges may still need polished finish for safety.
• Great for bathroom vanities, full bathroom walls, dressing rooms, hallway mirrors.

8 mm mirrors

• Premium thickness often used in gym walls or large commercial installations.
• Sturdy enough for large panels with minimal framework.
• Requires stronger fixings, heavier backing, and more careful handling.
• Best for mirror walls, large panels in gyms, or spaces where the mirror is a feature element.

Which thickness for which setting

• Small bathroom mirrors with frames → 4 mm is usually sufficient.
• Wall-mounted mirrors in living areas or bathrooms → 6 mm balances durability and cost.
• Gym walls or large feature mirrors → 8 mm delivers premium strength and minimal flex.
• Always specify polished or smooth edges if edges will be exposed.
• If in doubt, talk to your supplier about custom cut options and safety ratings.

For high quality cut-to-size mirror panels, check out Custom Mirrors or Tempered Glass if you want safety-certified options.

Sources & further reading:
GGF Glass Specification for Vertical Mirror Installations,
Trada Architectural Mirrors Design Guide

Frequently asked questions

Is 4-mm mirror strong enough for a large wall?
Probably not—it will flex and may develop warping. Choose 6-mm or 8-mm for large spans.

Does thickness affect mirror clarity?
Not directly—clarity more depends on glass quality and backing. But thicker mirrors can seem more stable and less prone to distortion.

Are polished edges necessary?
Yes for exposed edges—polished or bevelled edges reduce risk of cuts and improve appearance.

Does tempered mirror make a difference?
Tempered mirrors add safety—when broken, tempered glass crumbles into small granular pieces rather than large shards. If safety is a concern (e.g. gym setting), look for tempered or safety-graded mirrors.

How much more expensive is 8-mm vs 6-mm?
Expect higher cost due to thicker material, heavier shipping, more precise cutting, and possibly upgraded mounting hardware. But cost difference is often justified for premium look and durability.

Step-by-Step Guide · 2025

Read time: ~7 mins · Updated: 21 Sep 2025

Ordering the wrong size replacement window glass can cost time, money, and stress.
With just a tape measure and careful checks, you can measure correctly the first time and make sure your glass fits perfectly.
This UK homeowner’s guide will take you step-by-step through measuring width, height, and squareness for new glass panes.

Tools you need

• Steel tape measure (avoid cloth or flexible tapes)
• Notepad & pen (record each measurement)
• Helper (optional but useful for large windows)

Step 1: Measure the width

Measure the opening’s internal width at the top, middle, and bottom. Write down all three measurements and use the smallest as your final width.
This ensures the new glass won’t be too wide for tighter sections of the frame.

Step 2: Measure the height

Measure the internal height on the left, centre, and right. Again, take the smallest measurement as your final height.
Frames often aren’t perfectly square—this method ensures a safe fit.

Step 3: Check squareness

Measure diagonally from top left to bottom right, and top right to bottom left.
If the difference between the diagonals is more than 5 mm, your frame is out of square.
This is important to tell your supplier so they can help you adjust or recommend the best fitting method.

Step 4: Finalise your order

• Deduct a small fitting tolerance (usually 2-3 mm) from both width and height.
• Specify the type of glass: toughened, laminated, patterned, or double-glazed unit depending on your needs.
• Request polished edges for safety if edges will be exposed.
• Confirm compliance with UK safety standards (BS EN 12150 / BS EN 14449).

Frequently asked questions

Do I measure the old glass or the frame?
Always measure the frame opening, not the broken glass. Glass can shrink or chip, so relying on it risks ordering the wrong size.

Should I deduct size myself?
Yes, usually deduct 2-3 mm from both width and height to allow fitting tolerance. If unsure, confirm with your supplier.

What if my frame is not square?
Note down the diagonal difference and inform your supplier. In some cases, a slightly smaller pane or special fitting is advised.

Is toughened glass required?
Yes, if the glazing is within 800 mm of the floor or in a door/side panel. For guidance, see FENSA.

Can I install it myself?
Small single panes can be DIY, but for large or double-glazed units, professional fitting is recommended for safety and compliance.

UK homeowner’s guide. This walkthrough shows you how to fit a frameless glass shower door cleanly and safely — from measuring and drilling tiles to aligning hinges, sweeps and seals for a leak-free finish. If you’re comparing glass strength types, read our short primer on tempered glass first.

Overview

A frameless door relies on precise measuring, correct hinge placement and the right seals. Most domestic doors are 8–10 mm toughened glass with two hinges, a bottom sweep, and optional magnetic or edge seals. Plan slowly, work methodically, and use neutral-cure silicone around wet joints.

Safety & Prep

• Weight: A 900×2000×10 mm panel can weigh ~45–50 kg. Always lift with two people and suction cups.
• PPE: Gloves, eye protection, long sleeves; protect edges and corners at all times.
• Electrics: If drilling near cables/sockets, isolate power and scan the area.
• Glass facts: Toughened glass cannot be cut or drilled after manufacture — sizes and cut-outs must be final. Learn more about tempered glass.

Tools & Materials

• Two suction cups, soft pads, 1–2 mm plastic packers
• Spirit level, square, masking tape, pencil
• Drill/driver, low-speed setting; diamond or carbide tile bits
• Wall plugs/fixings for your substrate (tile over board/brick/stone)
• Neutral-cure sanitary silicone (clear) & sealant gun
• Hinges + gaskets, handle, bottom sweep & side seals (as supplied)
• Isopropyl alcohol (IPA) and lint-free cloths

Measure & Order

1. Opening survey: Measure width at top/middle/bottom; height left/centre/right. Note the smallest numbers and any out-of-square.
2. Hinge side: Decide left or right swing; check obstacles (vanity, towel rail, WC).
3. Threshold: Check the tray/floor is level. A slight inward fall towards the shower is good; outward fall needs correcting.
4. Deduct tolerances: For wall channels, the manufacturer specifies deduction. For wall-to-hinge glass (no channel), confirm hinge set-outs and seal allowances with the supplier.
5. Order spec: Thickness (8–10 mm), hinge cut-outs (or channel), handle holes, clear polish edges, and safety stamp.

Installation Steps

Tip: Mask reference lines so you can mark accurately on finished tile. Work slowly; accuracy beats speed.

1. Mark hinge positions: Offer the hinge side/channel to the wall; use a level to mark the vertical line. Mark fixing holes through the hinge plate or channel.
2. Drill the tiles: Use a sharp diamond/tile bit on low speed. Start at a shallow angle to score the glaze, then go square. Do not hammer drill through the tile. Swap to masonry bit only after clearing the tile if the substrate requires it.
3. Fix wall hardware: Insert appropriate plugs. For channels: run a thin bead of silicone behind the channel (moisture barrier), then screw off plumb. For surface-hinges: fit the back plates level, using the supplied gaskets.
4. Dry-fit the door: With two people and suction cups, lift the glass onto packers. Engage hinges loosely. Check gaps to the wall, tray and head; adjust as needed. This is where you perfect alignment.
5. Tighten hinges correctly: Fit all gaskets; never allow metal to touch glass. Tighten evenly to the manufacturer’s torque guidance — firm, not brutal.
6. Fit handle & sweep: Install the handle with its gaskets. Cut the bottom sweep to length and push it on; the fin should just kiss the threshold for smooth closing without scraping.
7. Edge/magnetic seals: If supplied, push-fit along the latch side or fixed panel. Ensure the magnets meet with a gentle draw, not a slam.
8. Final alignment: Close the door and check: even gaps, consistent sweep contact, smooth swing without self-opening. Use hinge adjustments to correct drift (out-of-level causes creep).
9. Seal as needed: Silicone the outside perimeter where glass meets wall channel and where the channel meets tile. Do not trap water by sealing both inside and outside; follow the hinge/channel instructions.
10. Cure time: Leave silicone to cure fully (often 24 hours) before heavy showering or cleaning.

Clearances & Tolerances (Quick Reference)

Common Mistakes (and Fixes)

• Over-tightening hinges: Can bruise glass or warp alignment. Loosen, re-seat gaskets, re-tighten evenly.
• Wrong silicone: Acetoxy (vinegar smell) near back-paint/metal can cause issues — use neutral-cure.
• Sealing inside and outside: Traps water; only seal as the hardware instructions specify.
• Ignoring fall of the floor: If water runs outward, adjust sweep angle or correct the threshold before sealing.
• No dry-fit: Always test with packers and tape before final tightening.

Aftercare & Maintenance

• Daily: Quick squeegee after showers to prevent mineral lines.
• Weekly: pH-neutral cleaner + microfibre on glass and hardware; never abrasive pads.
• Quarterly: Check hinge screws and seals; replace yellowed sweeps. Consider a protective coating to slow limescale.

FAQs

8 mm or 10 mm?
Both are common. 10 mm feels more premium/heavy; 8 mm is lighter and easier to hang. Either way, use properly rated hinges and fixings.

What causes drips at the hinge side?
Usually a missing or incorrect seal, or the door not sitting plumb. Re-seat gaskets, add the correct seal and re-align.

My door drifts open/closed by itself — why?
The opening or hinge line is slightly out of level. Use hinge adjustment (if available) or re-shim the plate.

Is laminated glass better than toughened?
Laminated adds a bonded interlayer that holds fragments; toughened breaks into small cubes. For most shower doors, toughened is standard — learn the basics on tempered glass.

Not sure about hinges or seals? Ask Glass Helper for quick advice or professional installation.

Back-painted glass splashbacks look sleek, wipe clean in seconds, and protect the wall from heat and splashes. Here’s a clear, UK-friendly guide to fitting one safely and neatly.

Before You Start (Important)

• Use toughened (tempered) glass only near hobs. Learn more about tempered glass. Toughened glass cannot be cut or drilled after manufacture.
• Check cut-outs (sockets, switches) were made at the factory and edges are polished.
• Compatibility: Use a neutral-cure silicone or approved high-tack adhesive suitable for back-painted glass. Avoid solvent-based adhesives that can attack paint.
• Heat clearance: Follow your hob manufacturer’s guidance. Keep required distance or fit a heat shield if specified.

Tools & Materials

• Suction cups (2x) & 1–2mm plastic packers
• Spirit level & masking tape
• Neutral-cure sanitary silicone / approved panel adhesive
• Degreaser (isopropyl alcohol), lint-free cloths
• Sealant gun & profiling tool

1) Prep the Wall

Remove dust and grease; fill high/low spots. The surface must be flat, dry and sound (painted plaster, primed plasterboard, or existing tiles are fine if solid). Degrease the wall and the back of the glass (avoid the painted face).

2) Mark Your Level Line

Offer the panel up with suction cups. Check level and gaps to worktops, cabinets and sockets. Lightly mark a level reference line with masking tape.

3) Dry Fit with Packers

Place 1–2mm packers on the worktop or upstand where the panel will sit. This gives a neat shadow line and room for sealant.

4) Apply Adhesive

Run vertical beads or golf-ball-sized blobs at 100–150mm centres across the back (unpainted edges). Keep 20mm in from the perimeter so adhesive doesn’t squeeze out. Do not smear the whole back; leave air paths so curing can occur.

5) Set the Panel

1. Lift with suction cups; angle the bottom edge onto the packers.
2. Rotate gently back to the wall, aligning to your tape line.
3. Press evenly across the surface — don’t hammer or lever against corners.

6) Check Level & Hold

Confirm level. If needed, use low-tack tape across the face to hold while adhesive grabs.

7) Seal the Perimeter

Mask both edges, then run a continuous neutral-cure silicone bead around the perimeter (worktop joint and verticals). Tool once, then remove tape immediately for a crisp edge.

8) Curing Time

Follow adhesive instructions. Typical: 24–48 hours before heavy cleaning or heat exposure.

Pro Tips

• If installing behind a gas hob, confirm minimum distance or use a heat-rated backer as per manufacturer guidance.
• For long runs, consider expansion gaps at ends (2–3mm) — hide with silicone.
• Colour matching: request a sample or RAL reference before ordering the final panel.

Common Mistakes to Avoid

• Using acetoxy silicone (vinegar smell) which can damage paint or metal — choose neutral-cure.
• Skipping packers (panel can bind on worktop and crack during settlement).
• Forcing a panel over out-of-square walls instead of correcting the substrate.

FAQs

Can I stick onto tiles? Yes, if tiles are solid and degreased. Rough up glossy tiles lightly for better grab.

What thickness is best? 6mm is a common, premium choice for kitchens; 4mm can work on smaller panels. Read more about tempered glass.

How do I remove one later? Carefully cut the silicone edge, then use a wire/cheese-cut to separate adhesive pads. Wear eye protection and gloves.

Not sure about clearances or adhesives? Ask Glass Helper for a quick recommendation.