Glazing Advice Centre: how-to guides, rules and quick answers from London glaziers
Straight answers from glaziers who fix windows and doors across London every day. Find your problem in the table, follow the guide, and if it turns out to be a job for us, send a photo on WhatsApp or call 07915 903485. Every guide says plainly what you can do yourself and when to stop.
What's wrong with my window or door?
Start here. Find the symptom, see the likely cause, and open the guide that fixes it.
| What you notice (tap for the guide) | Likely cause, and can you fix it yourself? |
|---|---|
| Mist or droplets between the panes | Failed sealed unit. DIY: no, new unit |
| Water on the room side of the glass | Room humidity. DIY: yes |
| Door only locks if you lift the handle hard | Door has dropped on its hinges. DIY: yes, usually |
| Window scrapes the frame or won't lock | Worn hinges or cams out of line. DIY: often |
| Handle floppy or spins | Failed gearbox. DIY: no |
| Draught or whistle with the window shut | Worn gasket or poor compression. DIY: often |
| Rattling sash windows | Worn beads and brush pile. DIY: sometimes |
| Traffic noise keeps you awake | Gaps and standard glass. DIY: partly |
| Mould on window reveals in winter | Vents closed, poor ventilation. DIY: yes |
| Scratch across the glass | Surface damage. DIY: light scuffs only |
| Glass broken right now | Impact, break-in or storm. DIY: make safe only |
Glass types at a glance
The cheat sheet we use when customers ask "what glass should go here?"
| Glass | What it does, and where it goes | Safety glass? |
|---|---|---|
| Float | Ordinary clear glass. Upper panes, small windows away from doors. | No |
| Toughened | Several times stronger, breaks into small blunt pieces. Doors, low panes, showers, splashbacks. | Yes |
| Laminated | Cracks but holds together on a plastic layer. Shopfronts, rooflights, security glazing. | Yes |
| Acoustic laminated | Laminated with a sound-damping layer. Bedrooms on busy roads. | Yes |
| Low-e | Thin coating that reflects heat back into the room. Inner pane of modern double glazing. | No, unless also toughened or laminated |
| Obscure | Patterned for privacy. Bathrooms, front door panels. | Only if toughened or laminated |
| Georgian wired | Wire mesh inside, for fire resistance. Older doors and fire screens. | No |
More detail: toughened vs laminated glass, double vs triple glazing and secondary vs double glazing.
The rules in 60 seconds
- Replacing a whole window or external door? It must meet the Building Regulations, shown by a FENSA or CERTASS certificate, or by building control. See FENSA certificate explained.
- Replacing just the glass? That is a repair: no certificate needed.
- Glass in doors, beside doors or low down? It must be safety glass. See where safety glass is required.
- New windows? They should not reduce the room's ventilation, which usually means trickle vents. See trickle vents.
- Upstairs bedroom window? It may be a fire escape: restrictors must release without a key. See window restrictors.
- Listed building or conservation area? Planning rules apply too. See conservation area glazing.
Twice-a-year window and door checklist
Ten minutes in spring and autumn keeps windows and doors working for years. Screenshot it, print it or share it with your landlord.
- Clear the drainage slots along the bottom of every window and door frame.
- Wash frames and gaskets with warm soapy water, never solvents.
- Put a drop of light oil on hinges, locking cams and the door lock along the edge.
- Close each window on a strip of paper: if it slides out, adjust or re-seal.
- Lift each door handle: if it needs force, adjust the hinges now, before the lock breaks.
- Check every pane for mist between the glass.
- Open every trickle vent and vacuum out the dust.
- Test each window restrictor and its release.
- Look at the frame corners for cracks, gaps or soft timber.
Want to know how long it will all last? Read how long double glazing lasts.
Broken glass right now?
Make the area safe, keep people and pets away, photograph the damage for your insurer and call us. We run emergency glazing 24/7 across Central and North London. Read what to do after a break-in and the broken window insurance claim guide while you wait.
Getting a job done
- Measure for replacement glass, so a quote is right first time.
- How to choose a glazier in London and what a glazier costs.
- Book a free survey and quote for new windows and doors.
Every how-to guide
FENSA Certificate Explained: Do You Need One?
What a FENSA certificate is, when replacement windows and doors need one, what it does not cover, and how to get a copy of a lost certificate when you sell.
How Long Does Double Glazing Last? Repair or Replace
How long double glazing lasts, part by part: sealed units, frames, hinges and gaskets, the signs each is failing, and how to choose repair or replacement.
How to Adjust a uPVC Door That Has Dropped
uPVC door catching, hard to lock or letting in draughts? How to adjust the hinges and keeps step by step, which hinge type you have, and when to stop and call.
uPVC Window Won't Close or Lock? How to Fix It
A uPVC window that sticks, drags or will not lock is usually hinges, keeps or a tired gasket. Step-by-step checks, what to adjust and when to call a glazier.
How to Measure for Replacement Glass (Step by Step)
How to measure a window for replacement glass or a sealed unit: rebate sizes, deductions, unit thickness and the photos a glazier needs. Free WhatsApp check.
How to Remove Scratches From Glass (What Works)
How to remove scratches from window and door glass: the fingernail test, polishing light scuffs, why WD-40 only hides them, and when to replace the pane.
How to Replace Window Seals on uPVC Windows
Can you replace window seals yourself? How to identify the gasket, remove the old seal and fit a new one on uPVC windows, and when it is the glass instead.
How to Soundproof Windows in a London Home
How to soundproof windows against traffic and street noise: quick fixes, acoustic laminated glass, secondary glazing and what works on a busy London road.
Blown Double Glazing? 5 Tests to Tell If It Has Failed
Five quick tests to tell if a double glazed unit has failed: mist between panes, the lighter test, cold spots, rainbow film and draughts. What each one means.
Trickle Vents: Do You Need Them on New Windows?
What trickle vents do, when replacement windows need them, whether you can close or cover them, and how they cut condensation and mould in London homes.
Where Is Safety Glass Required? UK Rules Explained
The UK critical locations for safety glass in plain English: doors, panels beside doors and low glazing, with heights, a room-by-room checklist and what to fit.
Window Restrictors: Child Safety Guide and How to Fit
Window restrictors explained: which type suits uPVC, sash and aluminium windows, how to fit one, how to release it in a fire, and what landlords should check.
About the Advice Centre
Can I fix my own windows and doors?
Many small jobs, yes: adjusting a dropped uPVC door, tightening hinges, fitting a new handle or replacing a gasket. Our how-to guides show each one step by step and say clearly when to stop. Anything involving broken glass, height, a failed lock gearbox or a window stuck open is safer left to a glazier.
Is your advice free?
Yes. Every guide in the Advice Centre is free to read, and you can send a photo of your window or door on WhatsApp for a free opinion on what is wrong and whether it is a DIY job.
How do I know if I need a repair or new windows?
Look at the frame. A sound frame with misted glass, draughts or a stiff handle needs a repair: new units, gaskets or hardware. A cracked, warped or rotten frame needs replacing. Our guide to how long double glazing lasts has a full repair-or-replace checklist.
Do you only give advice for North London?
The guides apply to homes anywhere in England, though the examples come from the London homes we work in every day. Our repairs and installations cover Central and North London, and emergency glazing runs 24/7.