Category: News

If a door contains glass, or sits right beside glass, the glass almost certainly has to be safety glazing. In England, Approved Document K says glass in a door leaf, glass within 300mm of a door edge up to 1500mm from the floor, and low-level glass within 800mm of the floor must either break safely, be robust, or be protected. Toughened glass is the most common way to meet that rule. Scotland has its own handbook, with very similar wording.

This guide explains the rules in plain terms. It covers where the requirement applies, which marks and standards to look for, how toughened glass differs from laminated glass, and what changes for commercial doors and housing association buildings. It also covers what to do if your existing door glass does not comply.

The short answer: where toughened glass is needed

Building regulations talk about “critical locations”. These are the places where people are most likely to collide with glass, fall against it or push through it. According to Approved Document K for England, the typical critical locations are:

• Any glazing within a door leaf, whatever its size.
• Glazing in a side panel or window within 300mm of the edge of a door, where it is also within 1500mm of the floor.
• Glazing in walls and partitions that sits wholly or partly within 800mm of the floor.

In practice, this means a glazed front door, a patio door, a back door with a vision panel and a side light next to an entrance door will nearly always need safety glazing. The same goes for the low panes in a conservatory door set.

Note the wording “wholly or partly”. A pane that starts at 700mm and rises to 2000mm still counts, because part of it falls inside the 800mm zone.

A quick check you can do yourself

Stand at the door and look at each pane of glass. Ask three questions:

1. Is the glass part of the door itself?
2. Is the glass beside the door, with any part of it within 300mm of the door edge and below 1500mm from the floor?
3. Does any part of the glass sit below 800mm from the floor?

A “yes” to any of them means the glass is in a critical location. Then look for the permanent mark in the corner of the glass (more on that below). If you cannot find one, do not assume the glass is compliant.

What “safety glazing” actually has to do

The requirement is called K4 in England. It does not name toughened glass as the only answer. Instead, Approved Document K sets out three routes for glazing in critical locations:

• Break safely. If the glass breaks, it does so in a way that is unlikely to cause serious cuts. The document refers to BS EN 12600 Class 3 or BS 6206 Class C.
• Be robust. The glass is thick or strong enough to resist impact. Small panes are one example.
• Be permanently protected. A guard or barrier stops people from striking the glass.

For most homes and shops, the first route is the practical one. You fit glass that has been tested and marked to the right class, and the question is settled.

Why toughened glass fits the brief

Toughened glass is heat-treated during manufacture. As one UK glass supplier explains, it is up to five times stronger than regular glass, and if it does shatter it breaks into small pieces that cause less serious injuries than the large shards of ordinary glass. We cover the benefits in more detail in our guide to toughened glass benefits for UK properties, and our explainer on what toughened safety glass is is a good starting point if the term is new to you.

One practical point matters here. Toughened glass cannot be cut or drilled after treatment. It is made to size first, then toughened. That means the replacement unit must be measured accurately before it is ordered, and any holes for handles or letterboxes must be specified in advance.

Spotting compliant glass: marks and standards

Safety glass should carry a permanent mark, usually etched in one corner. It typically shows the manufacturer or supplier, the standard (BS EN 12150 for thermally toughened glass, or BS EN 14449 for laminated) and the impact class, such as 1C1 or 2C2 under BS EN 12600.

BS EN 12600 is the impact test most often referred to for glass in doors. It grades glass by how it behaves when struck by a heavy impactor, and the class tells you the height from which it survived or broke safely.

If you are reading an old specification, you may see BS 6206. It was the earlier standard, and Approved Document K still recognises Class C under it.

Two things to bear in mind:

• A mark in a corner of one pane does not prove every pane in the door is safety glass. In a double glazed unit, both panes in a critical location should be safety glazing. Check both sheets.
• Some older doors were fitted before the rules were tightened, or with ordinary glass that was never replaced. The glass may look sound and still not meet today’s standard.

England and Scotland: two rulebooks, one common idea

Building regulations are devolved. England follows the Approved Documents. Scotland uses the Building Standards Technical Handbook. Wales and Northern Ireland have their own versions, so check the local authority if you are outside England and Scotland.

England

Approved Document K covers the rule described above. Whether a particular job needs building control sign-off depends on the work. Replacing glass in an existing door with like-for-like safety glass is a different job from fitting a brand-new glazed opening. If you are unsure, ask your local building control team before work starts.

Scotland

The Scottish handbook, section 4.8, says glazing in a door leaf, or within 300mm of a door leaf and within 1.5m of floor level, should be safety glazing. The same section covers glazing wholly or partly within 800mm of floor level: it should resist impact, break safely or be protected by guarding.

There is one Scotland-specific detail worth noting. An unframed glazed door operating on a pivot must have any exposed vertical edge highlighted so that it contrasts visually with its surroundings. This matters for frameless glass doors in shops and offices.

For more on the Scottish position, see our guide to window safety regulations in Scotland.

Toughened glass or laminated glass?

The question “what is the difference between toughened glass and security glass?” comes up often, because the two do different jobs.

• Toughened glass is heat-treated. It is strong and, when it breaks, it crumbles into small granular pieces. That is why it is called a safety glass.
• Laminated glass has a plastic interlayer between two sheets. When it breaks, the pieces stay stuck to the interlayer, so the pane tends to hold together.

As a UK glazing professional notes, building regulations focus on whether glazing in critical locations will not break or will break safely, and both toughened and laminated glass can meet that safety requirement.

So the regulation does not force you to choose toughened over laminated. The choice comes down to what else you want the door to do.

The last row has a practical consequence. A West Sussex County Council construction guide explains that laminated glass is preferred for high-security uses and for reglazing where rebate depths allow, and that it can be cut to size locally, unlike toughened glass.

Security is a separate question

Safety and security are not the same thing. Safety glazing protects people from injury. Security glazing resists attack. Scottish guidance in section 4.13 of the handbook recommends preventing access to door locks from outside by breaking adjacent glazing, using laminated or similarly robust glass.

If a pane sits within arm’s reach of your lock, laminated glass is worth considering. Our guides on laminated glass for doors, why use laminated glass and P1A laminated glass for door security go into the detail. If you are comparing the full range, our types of safety glass guide sets them side by side.

Commercial doors and shopfronts

Business premises have a few extra points to cover on top of the critical-location rule.

Manifestation

Approved Document K requires transparent glazing in non-domestic buildings to incorporate features that make it apparent. This is known as manifestation. It usually means bands, logos or frosted patterns at eye level. The requirement does not apply to dwellings.

Many shops meet this with decals or etched graphics. If you apply them yourself, the way they are fitted matters, and a guide on getting window stickers to stick shows the installer checks that keep graphics in place on glass.

Door widths

Glass is only part of the picture. Approved Document M, Volume 2 sets the minimum effective clear width for entrance doors in new non-domestic buildings at 1000mm, and internal doors typically need at least 800mm. This is a common question alongside glass, but it applies to the door opening, not to the glazing. When you swap glass only, the door and frame stay the same, so the opening width does not change.

This is one reason why glass-only work is useful for premises that are already in use. You can bring door glazing up to standard without altering the structure.

Fire doors

If a glazed door is also a fire door, extra rules apply. Fire-rated glass is a different product from ordinary toughened glass, and the glazing, the beading and the frame work as a system. Replacing the glass with the wrong type can undo the door’s fire rating.

For residential buildings, the Fire Safety (England) Regulations 2022 require responsible persons in buildings above 11 metres with two or more sets of domestic premises to check communal fire doors at least every 3 months. They must also use best endeavours to check flat entrance fire doors at least every 12 months. The government fact sheet on regulation 10 adds that information about fire doors must be given to residents of multi-occupied residential buildings with common parts.

If a check finds damaged or cracked glazing in a fire door, do not simply swap in toughened glass. Get the door assessed first.

Our perspective

Most of the glass problems we are called to are not dramatic. A homeowner has a misted unit in a back door, or a tenant reports a cracked panel in a communal entrance. The question then is what the replacement glass has to be.

Our experience is that the critical-location rule catches people out more than any other. A pane looks like part of an ordinary window, but it sits low, or close to the door edge, and it was never safety glass. When we replace glass only, we start by checking exactly where the pane sits and what the marks on the old unit say.

We also think safety and security should be discussed together. If the pane has to be safety glazing anyway, it costs nothing to ask whether it is next to a lock and whether laminated glass would suit it better. That is a decision for you, and we would rather explain the options than push one.

Because we replace only the glass and leave the frame in place, the job is usually quicker and less disruptive than replacing the whole door. That matters when a door is a business entrance or a communal route.

What to do if your door glass may not comply

Not every older door needs urgent action, but a cracked, misted or unmarked pane in a critical location is worth dealing with. Follow these steps.

1. Identify the critical panes. Use the 300mm, 800mm and 1500mm checks above.
2. Look for the etched mark. Check each pane in a double glazed unit, not just one.
3. Note the damage. Cracks, misting between panes, and failed seals each need a different fix.
4. Check the frame. Glass-only work depends on a sound frame and sufficient rebate depth, especially if you want laminated glass.
5. Ask for the standard in writing. A competent installer will tell you which class of glass is going in and where the mark will be.
6. Keep the paperwork. For rented property, social housing and commercial premises, records of what was fitted help during inspections.

Our page on double glazed door repairs covers door glass, and if a pane has already broken, see broken window repairs. For conservatory doors and low-level roof-line glazing, there is a dedicated conservatory window repair service.

Housing associations and property managers

If you manage a block or a portfolio, door glass can turn into a compliance list. A reliable approach is to survey the glazed doors and side panels, record which carry the safety mark, and flag fire doors for separate assessment. Our inspection service and full replacements are set up for this kind of work, and our commercial window repair page covers business premises.

Getting compliant door glass from Cloudy2Clear Windows

We have been installing, replacing and repairing double glazed windows for homes and businesses since 2005. We replace only the glass, not the frame, which keeps disruption low, and our work comes with a 25-year guarantee. You can see what is involved on our double glazing replacement page, or get in touch through our main site. Our lines are staffed Monday to Friday, 8:30am to 6:30pm.

If you also want better insulation or less noise from a door unit, ask about insulating glass and soundproofing glass at the same visit.

Frequently asked questions

Does every glazed door need toughened glass?

Glass in a door leaf is a critical location, so it needs safety glazing. Toughened glass is the usual choice, although laminated glass can also meet the rule. The glass must carry a recognised mark to show it has been tested.

Can I use laminated glass instead of toughened glass in a door?

Yes, provided it is marked to the right impact class. Laminated glass holds together when broken, which makes it a good option near locks. Check that the frame has enough rebate depth to take it.

Do the rules differ in Scotland?

The principle is the same, but Scotland follows the Building Standards Technical Handbook rather than Approved Document K. Section 4.8 sets the door leaf, 300mm and 800mm tests, and it adds a rule for exposed edges of unframed pivot doors.

How do I tell if my door glass is safety glass?

Look for a permanent etched mark in a corner of each pane, showing the standard and class. If you cannot find one, or the unit is old, ask a glazier to inspect it. Do not rely on thickness or appearance alone.

Does replacing only the glass in a door need the frame changed?

Not usually. Glass-only replacement works when the frame is sound and the rebate is deep enough for the new unit. A survey will confirm this before any glass is ordered.

Sources

• Approved Document K: Protection from falling, collision and impact
• Scottish Building Standards Technical Handbook 2020, 4.8 Danger from accidents
• Scottish Building Standards Technical Handbook 2020, 4.13 Security
• Approved Document M, Volume 2, with 2024 amendments
• The Fire Safety (England) Regulations 2022, regulation 10
• Fire doors (regulation 10) fact sheet, GOV.UK
• When do I need safety glass in doors and windows, and what type
• Property Services Construction Guide: glazing, West Sussex County Council
• When do you need toughened glass?

If you let a home in the UK, you are almost always the one responsible for repairing its windows and glazing. In England and Scotland the law treats windows as part of the structure and exterior of the property, so a misted unit, a cracked pane or a failed lock is normally your job to put right, whatever the tenancy agreement says. This guide covers where that duty comes from, how Scotland differs and what counts as urgent.

The short answer: windows belong to the landlord’s repair duty

GOV.UK states that landlords are always responsible for repairs to the structure and exterior of a rented property. Windows, frames, sills and the glass in them sit within that. Shelter England lists windows among the repairs landlords must carry out, and says this applies even when the tenancy agreement is silent on the subject.

In practice, that covers cracked or smashed glass, failed sealed units, rotten or warped frames, broken handles, hinges and locks, and gaps around frames that let in wind and rain.

A tenant cannot be made to fix any of this. GOV.UK is clear that tenants cannot be forced to do repairs that are their landlord’s responsibility.

What the law says in England

Three pieces of legislation shape your duties in England. Torbay Council summarises them as section 11 of the Landlord and Tenant Act 1985, the Homes (Fitness for Human Habitation) Act 2018 and the Housing Act 2004, which introduced the Housing Health and Safety Rating System (HHSRS).

Fitness for human habitation

The GOV.UK guide to the Homes (Fitness for Human Habitation) Act 2018 says landlords must make sure a rented home is fit to live in at the start of the tenancy and throughout it. A court looks at matters such as disrepair, instability, serious damp, and inadequate natural light and ventilation. Every one of those can be caused or worsened by faulty windows.

Under the HHSRS, councils can inspect for hazards and take enforcement action where serious ones exist.

What a good standard looks like

Local authorities spell out what they expect. Manchester City Council says landlords should keep external doors and windows solid, in good repair, suitably draught-proofed and fitted with suitable locks. The same page says that where timber frames are so rotten that repair is unreasonable, they should be replaced.

What the law says in Scotland

Scotland has its own regime, and it is worth knowing if you let property there or manage a mixed portfolio. The Repairing Standard guidance, which applies from 1 March 2024, says the structure and exterior of a privately rented house must be in a reasonable state of repair and proper working order. The test takes into account the age, character, prospective life and locality of the building.

The Scottish Government’s tenancy notes go further on windows. They say the landlord’s structural repair duty includes outside doors, windowsills, window catches, sash cords and window frames. The same page says the property must be wind and watertight and fit to live in, and gives an example of non-compliance: gaps between window or door frames and walls that let wind or rain enter.

Two further points matter. The landlord must meet the standard before and throughout the tenancy, and repair defects within a reasonable time after being told. And using a letting agent does not move the duty: mygov.scot confirms that you stay responsible, and that a tenant can take you to a housing tribunal if the property fails.

If you own property in Scotland, our guide to window safety regulations in Scotland covers the wider rules, and our best window types for Scotland article helps if a repair turns into an upgrade conversation.

England and Scotland compared

Do windows have to open in a rented property?

This is a common question, and there is no tidy single rule to quote. The better way to think about it is through the duties above. A home must have adequate natural light and ventilation to be fit for human habitation, as the GOV.UK landlord guide sets out. A window that has been painted shut, has a seized hinge or has a broken handle may stop a room being ventilated properly, and in a bedroom it may also matter for escape in a fire.

Treat every habitable room as needing at least one window that opens, closes and locks properly. If you are unsure about a particular room, ask your local council or a fire risk assessor before you seal or change anything.

How quickly must you act?

Neither England’s private rented rules nor Scotland’s Repairing Standard set one fixed number of days for glazing. The standard is a reasonable time, and what is reasonable depends on the risk.

• Security risk: After a break-in or attempted break-in, Manchester City Council says the landlord should arrange at least a temporary repair straightaway. Boarding or a temporary pane restores security while a proper unit is made.
• Weather getting in: A cracked pane can quickly lead to damp, which becomes a habitability issue.
• Misted units and stiff handles: These are less urgent, but they should not be left.

GOV.UK advises tenants to contact their landlord straight away when something needs repair. A landlord who answers promptly and records what was done is in a far stronger position than one who lets the report sit.

Housing associations and social landlords in England

The timetable is tighter for social housing. From 27 October 2025, Awaab’s Law applies to England’s social rented sector. Social landlords must investigate potential emergency hazards and complete necessary safety work within 24 hours. The guidance gives broken external windows that present a home security risk as an example of an emergency hazard.

For a housing association, that makes glazing a same-day triage matter. Our article on housing association window repairs started in 24 hours shows how that works.

Scotland’s Right to Repair

In Scotland, the statutory Right to Repair scheme applies to Scottish secure and short Scottish secure tenants, not generally to private residential tenants. Qualifying repairs include external windows, doors or locks that are not secure, and the landlord must give the applicable maximum completion time.

Who pays when a window is damaged?

The starting point is simple: the repair duty sits with you, but responsibility for the cost can move when a tenant causes the damage. GOV.UK says tenants are responsible for paying for damage they cause, including damage caused by family and friends.

A fair approach looks like this:

1. Ordinary wear and failure: Misted units, rotten frames and worn locks are yours to deal with.
2. Damage by a tenant or visitor: The tenant is responsible for the cost, but arrange the repair promptly so the home stays secure.
3. Damage by a third party, such as a break-in: The repair is still urgent, and any insurance claim depends on your policy.

Document each window with dated photographs at the start of every tenancy, so disputes about who caused a crack can be settled.

Tenants also have a part to play in everyday care. Reporting faults early, keeping vents clear and looking after the property all help, and a regular routine such as keeping a rental home clean makes it easier to notice a seal failing, a cracked pane or a sticking catch before it becomes a bigger job.

If you do not act, tenants in England can contact the local council’s environmental health department, and in Scotland they can apply to the First-tier Tribunal. Keep a clear reporting route and a written trail of what was reported and when.

Our perspective: repair the glass, not the whole window

We have been repairing and replacing double glazing across the private and commercial sectors since 2005, and one pattern shows up again and again with rental properties. A landlord is told a window has failed, and the assumption is that the whole window must go. Very often it does not.

If the frame is sound and only the sealed unit has failed, the glass can be replaced on its own. That means less disruption for the tenant, a quicker turnaround, and a lower bill than a full window replacement. It is also the route to take when a frame is perfectly good and you simply want to bring a unit up to a better standard, with energy efficient or soundproofing glass in place of a tired older unit.

We would give landlords three pieces of advice:

• Inspect before a problem is reported. Our guide to identifying window issues in your property shows what to look for.
• Treat locks as part of the glazing. See our steps to repair window locks and our overview of security features in windows.
• Know when a frame is beyond saving. Where timber has rotted badly, glass-only work will not solve it, and we will say so.

Our 25-year guarantee and nationwide coverage mean you can fix a property once.

Commercial and housing association properties

Commercial premises have different duties, and housing associations carry the extra obligations described earlier. A periodic inspection of all glazing, a written record and repairs ordered by risk work better than reacting to every report. We offer an inspection service and full replacements, plus commercial window repair.

A practical checklist for landlords

Use this before each new tenancy and at every routine inspection.

1. Check that every window closes fully, with no gaps for wind or rain.
2. Look for fogging between the panes, which signals a failed seal.
3. Test every lock, handle and hinge.
4. Check that windows in habitable rooms open.
5. Photograph each window and date the record.

Getting glazing repairs done

If you need help with the glass, Cloudy2Clear Windows can repair or replace failed units without replacing the frame, and can also deal with double glazed door repairs, broken window repairs and locks, handles and hinges. Our office hours are Monday to Friday, 8:30am to 6:30pm. Contact us through our site to arrange a visit, or see our double glazing replacement page for how a unit swap works.

Frequently asked questions

Is a landlord responsible for broken windows?

Yes, in almost every case. Windows form part of the structure and exterior, and GOV.UK says landlords are always responsible for repairs to those. The exception is damage a tenant or their visitors cause, where the tenant may have to pay for the repair.

How fast must I repair a broken window?

The private rented rules ask for a reasonable time rather than a set number of days, and a security or weather risk makes the job urgent. For social landlords in England, Awaab’s Law sets 24 hours for emergency hazards, which can include a broken external window that creates a security risk. In every case, a temporary repair straight away is better than waiting for a perfect fix.

Do the rules differ in Scotland?

Yes. Scotland uses the Repairing Standard, which names window frames, sills, catches and sash cords. Tenants there can apply to the First-tier Tribunal, while in England they go to the local council.

Sources

• Private renting: Repairs, GOV.UK
• Landlord responsibilities for repairs, Shelter England
• Housing repair obligations, Torbay Council
• Guide for landlords: Homes (Fitness for Human Habitation) Act 2018, GOV.UK
• Doors and windows, Manchester City Council
• Repairing Standard statutory guidance, Scottish Government
• Repairs and maintenance obligations, Scottish Government
• Repairs and maintenance as a private landlord, mygov.scot
• Awaab’s Law: guidance for social landlords, GOV.UK
• Right to Repair, Scottish Government

Fitting a new window pane usually takes a few hours at most. The wait before that is often longer. A single-glazed pane can be cut and fitted in under an hour, while a double glazed unit is normally made to your measurements first, so the whole job runs over two visits spread across days. This guide explains both parts of the timeline, what can stretch it, and how to keep your home safe while you wait.

The short answer: two timelines, not one

When people ask how long a pane takes, they usually mean one of two things. Either they want to know how long the fitter will be in the house, or they want to know how long until the window is fixed. Those are very different numbers.

The figures are guides, not promises. Glass type, size, access and the frame all change them, and we explain each of those below.

Why double glazed units are not fitted the same day

A double glazed unit is two panes of glass separated by a spacer bar and sealed around the edge, with the gap between them filled with air or gas. It is built to fit one particular opening. A few millimetres out and it will not sit properly in the frame.

That is why a glazier cannot normally pull a replacement off the van. The unit has to be measured on site, ordered, manufactured and then brought back for fitting. Some work is quicker if the glass you need is a common size and specification, but you should not expect a same-day swap for a misted or failed unit unless the glazier has told you so.

Single-glazed panes are different. The glass is cut from a sheet, so it can often be measured and fitted in a single visit.

What happens on the day of the fit

Once the new glass arrives, the fitting visit is straightforward. For a typical uPVC window, the steps run like this:

1. Protect the area. Dust sheets go down and furniture near the window is moved back.
2. Remove the glazing beads. These are the thin strips that hold the glass in the frame. They are eased out carefully so they can be refitted.
3. Record the packers. Small plastic packers sit beneath the glass and help support its weight. Their positions are noted so they can be reproduced.
4. Lift out the old unit. A failed or broken pane is taken out and the glazing rebate, the channel the glass sits in, is cleaned.
5. Fit the new glass. The new unit is set on its packers and centred in the opening.
6. Refit the beads and check. Beads are clipped back, then the window is opened, closed and locked to make sure everything works.

This is the same sequence described in a trade guide to replacing a sealed unit in a uPVC window. The packing step matters more than it looks. On an opening window the packers carry the weight of the glass and keep the sash square, which is what lets it close and lock properly afterwards.

For most homes, one or two windows is a morning’s work. A whole house of failed units, or a large conservatory roof, takes longer simply because there is more glass to handle.

What can make the job take longer

Most delays come from the glass, not the fitting. These are the usual causes.

Safety glass has to be made to size

Glass in doors, in panels beside and above doors, and in low windows must be safety glass. Building guidance says safety glass is required in doors, glazing alongside and above doors, and glazing below 800 mm.

Toughened glass cannot be cut once it has been treated. It is cut to its final size and then heat-treated, so the same guidance allows about one week for manufacture and delivery. That is a council construction guide from 2004, so treat it as a sensible allowance for the process rather than a current quote. Laminated glass can be cut locally and supplied from stock, which is why it can sometimes be quicker.

If your broken pane is in a door or a low window, expect the glass to be the slowest part of the job. Our guide to what toughened safety glass is explains where it is required and why.

Special glass specifications

Standard clear double glazing is the quickest to organise. Glass with extra features usually takes longer to specify, check and make:

• Soundproofing or acoustic glass
• Energy-efficient glass with special coatings
• Obscure or patterned glass that has to match the rest of the house
• Laminated security glass for doors
• Leaded or decorative units in older properties

If you want an upgrade at the same time as the repair, it is worth saying so at the first visit. The glazier can then order the right unit once rather than twice.

Access and the state of the frame

A window on the ground floor with clear access is the easy case. Upstairs windows, bay windows, tall stairwell glazing and conservatory roofs need more time, more people or extra equipment. Commercial buildings add their own limits, such as working around opening hours or needing safe access to the outside of the glass.

The frame matters too. If beads are brittle, seals are perished or the frame has warped, the glazier may need to fix those before new glass can go in. That is one reason a proper look at the window beats a quote over the phone.

Odd sizes and unusual windows

Velux roof windows, caravan windows and old timber frames often use glass sizes and thicknesses that are not standard. Measuring is more careful, and manufacture may take longer. The result is worth the wait, because glass that fits well lasts longer and seals better.

Weather and access to your home

Fitting in heavy rain is difficult, especially when the frame is open and the bead channel is exposed. Bad weather can shift a booking. So can a tenant or occupier who is not available on the day, which matters for housing associations and landlords arranging several properties.

Replacing a single pane yourself

Single glazing is the one case where a DIY repair is realistic. A Guardian DIY guide to replacing a single-glazed pane lists about 45 minutes for the job. It is an older article, and it assumes you are confident cutting out old putty, handling glass and measuring accurately.

Sealed double glazed units are a different matter. They are heavier, unforgiving of poor measuring and easy to damage at the edges, and a badly packed unit can leave a sash that will not close properly. If your glass is double glazed, or the pane is in a door or at a height, a professional fit is the safer route. It also keeps the work properly guaranteed.

If your window has failed because the seal has gone, the glass itself is often fine and the frame is sound. In that case, replacing only the unit is quicker and less disruptive than replacing the whole window. Our article on why unit replacement beats full window replacement goes through when that applies.

Keeping your home safe while you wait

Because of the lead time for made-to-measure glass, a cracked or smashed pane can sit in your window for days. How you handle that gap matters.

• Do not pull out broken glass yourself. The Glass and Glazing Federation’s glass breakage guidance says broken glass can be razor sharp and advises people not to remove it from the framing themselves wherever possible.
• If you must handle it, the same guidance says to wear cut-proof gloves and safety glasses, and to protect other people where glass could fall, for example from high-level or sloping glazing.
• Keep children and pets out of the room until the glass has been made safe.
• Ask the glazier about temporary protection. Boarding or securing the opening keeps weather and intruders out while the new glass is made.

For a step-by-step approach, read our guide on how to remove broken glass safely. If the broken window is a business shopfront, our advice on the first hour after smashed shopfront glass helps you secure the premises and plan a quick reopening.

How we approach it at Cloudy2Clear Windows

We have installed, replaced and repaired double glazed windows for homes and businesses since 2005. Here is how we see the question of time.

The quickest way to get a window working again is usually to replace only the glass. If the frame is sound, there is no reason to remove it, make good the plaster and decorating around it, and wait for an entire new window to be made. Replacing the glass alone means a smaller job, less mess and a shorter wait. That is the principle our business is built on.

We also tell customers plainly that the made-to-measure stage is the part we cannot hurry. A unit that is rushed or measured badly causes more delay than it saves. So we would rather spend time at the survey, check the frame, note the glass type and confirm the specification before we order. When that is done properly, the fitting visit is short and the window works as it should.

Our glass replacements are backed by a 25-year guarantee, and we offer energy-efficient and soundproofing glass where you want an upgrade at the same time.

Getting your window fixed sooner

You cannot change how long a sealed unit takes to manufacture, but you can avoid adding days around it. These steps help:

1. Report the problem early. Misted units rarely fix themselves, and a cracked pane can fail further.
2. Take clear photos. Show the whole window and the damage, plus any labels or markings on the spacer bar if you can see them.
3. Note the location. Tell the glazier if the pane is in a door, low down, upstairs or in a conservatory, since that affects the glass type and access.
4. Decide on upgrades at the start. Soundproofing, energy-saving or security glass is far easier to order the first time.
5. Check access. Clear the area around the window and confirm who will be home for each visit.
6. List every window with a problem. Fitting several units in the same visit saves repeat call-outs.

If you manage a commercial building or a housing association stock, the same principles apply on a larger scale. Grouping windows by type and location keeps the programme efficient, and our commercial window repair team can plan around the way your building is used.

Book a glass replacement with Cloudy2Clear Windows

If you have a misted, cracked or broken pane, our double glazing replacement service replaces the glass without the cost and disruption of a new frame. For smashed glass, see our broken window repairs. Our phone lines are open Monday to Friday, 8:30am to 6:30pm, and we cover homes and businesses across England and Scotland. Send us a photo and a few details, and we will tell you what the job involves and how long it is likely to take.

Frequently asked questions

Can a window pane be replaced in one day?

A single-glazed pane often can, because the glass is cut to size and fitted in one visit. A double glazed unit normally cannot, because it is made to measure and has to be manufactured first. The fitting itself is usually the short part of the job.

How long does it take to fit a double glazed unit once it arrives?

Fitting is typically a matter of hours per window. The glazier removes the beads, lifts out the old unit, cleans the channel, sets the new glass on its packers, refits the beads and checks that the window opens and locks. Larger, heavier or harder-to-reach windows take longer.

Why does safety glass take longer?

Toughened glass must be cut to its final size before it is heat-treated, so it cannot be trimmed afterwards. That means it is made to order, and one council guide allows about a week for manufacture and delivery. Door glass and low windows usually need safety glass.

Is it safe to leave a cracked pane while waiting for new glass?

It is safer to keep the pane in place than to remove it yourself, unless it is loose or falling. Keep people away from it and ask your glazier about temporary boarding. If glass is hanging or at risk of falling, call a glazier straight away rather than handling it.

Do I need to replace the whole window if only the glass has failed?

Usually not. If the frame, hinges and seals are in good condition, the glass unit can be replaced on its own. A glazier should check the frame at the survey to confirm it is sound.

Sources

• Property Services Construction Guide: Glazing, West Sussex County Council
• Replace a single-glazed window pane, The Guardian
• Glass Breakage guidance, Glass and Glazing Federation
• How to replace a sealed unit in a uPVC double glazed window

Patio door draughts usually come from one of four places: worn seals, a door that has dropped out of alignment, a failed sealed glass unit, or gaps around the frame. Most can be found with a simple walk-round and a few minutes of checking. This guide shows you how to find the source, what you can safely fix yourself, and when a professional repair will do more good than another roll of adhesive strip.

Why patio doors let the cold in

A patio door has a long perimeter, a lot of glass and a locking mechanism that must pull the door tight against its seals every time you close it. If any one of those wears, you feel it.

The Energy Saving Trust explains that draught proofing stops unwanted cold air entering your home by sealing gaps around doors, windows and floors, which reduces heat loss and makes rooms more comfortable. Patio doors are often the biggest single opening on the back of a house, so they are a sensible place to start.

The usual culprits are:

• Compressed or perished seals. Rubber gaskets flatten and crack with age and sun exposure.
• Misalignment. Hinges or rollers wear and the door leaf drops or twists.
• Worn locking points. The keeps no longer pull the door tight.
• Gaps at the threshold. Debris, damaged tracks or a missing bottom seal let air under the door.
• Failed glass units. Misting between the panes suggests the seal has gone, and the glass loses insulating performance.

Find the draught before you fix it

Guessing wastes money and can leave a door that no longer closes. Spend ten minutes on diagnosis first.

1. Pick a cold, breezy day. The difference between inside and outside temperature makes leaks easier to feel.
2. Use the back of your hand. Move slowly around the edges, the lock side and the bottom.
3. Do the paper test. Close a strip of paper in the door at several points. If it slides out without resistance, the seal is not making contact there.
4. Look at the wear marks. Check whether the seals are flattened, split or missing in places, and whether the keeps on the frame show uneven scuffing.
5. Check the glass. Condensation or a cloudy film trapped between the panes points to a failed unit rather than a seal problem.

Check alignment first

Many homeowners reach for new weather strip when the real problem is mechanical. Frames can settle over time, especially in older properties, and the door leaf shifts so that locks and seals no longer make full contact. Checking alignment before assuming a seal needs replacing is often more effective, since extra stripping can interfere with smooth operation.

Signs that your door has dropped or shifted:

• The door rubs on the frame or the threshold.
• The handle is stiff to lift or the lock is hard to turn.
• You can see an uneven gap around the door.
• The door only feels secure if you lean on it while locking.

On hinged uPVC patio and French doors, hinge adjustment is often possible with an Allen key, and our guide to stopping uPVC door draughts covers seals and trickle vents in more detail. Sliding doors usually have adjustable rollers at the bottom of the leaf. If adjustment does not cure the problem, worn hinges, rollers or locking mechanisms are the likely reason, and these can be replaced without replacing the door. Our locks, handles and hinges repairs cover exactly this kind of wear.

Seals: what to look for and what to replace

If alignment is sound, the seals are next. Seals fall into a few broad types, and the right one depends on your door.

The Energy Saving Trust notes that if you have modern windows and doors with seals on the openings, they may already be draught proofed enough. So check whether your seals have simply worn out before adding anything on top.

Replacing a gasket in a modern door

Many uPVC and aluminium doors use a push-in gasket that can be pulled out and replaced. Profiles vary, so take a short length of the old seal with you when buying a replacement. Do not stretch the gasket as you fit it, because it will shrink back and open a gap at the corners.

Adding adhesive strip to older doors

On older timber doors, self-adhesive compression strip is a common fix. The Energy Saving Trust says the job needs careful measurement so the door can still close properly. If you have to force the handle up, the strip is too thick.

A note on period homes

If your property is listed or in a conservation area, think carefully before changing the doors. Local authority guidance, such as Bath and North East Somerset Council’s retrofit guidance, favours repairing original features and using discreet brush or compression seals. St Albans council guidance likewise says careful repair should be considered before replacement, especially where historic detail is involved.

Sliding patio doors: tracks, brushes and rollers

The leaf sits in a track, and draughts often come through the meeting stile, where the two leaves overlap, or along the track itself.

• Clean the track. Grit and dust stop the door seating properly and wear the rollers. A vacuum and a small brush do the job.
• Inspect the pile brushes. These small brush strips seal the sliding gap. When they flatten or fall out, the door loses its seal.
• Check the rollers. Worn rollers let the leaf sag, which opens a gap at the top corner of the meeting stile.

If you have had building or decorating work done recently, dust and plaster can clog tracks and brushes. Proper window cleaning after construction lets you see the real condition of the glass and frame before you decide what needs repair.

When the glass is the problem

Sometimes the cold you feel is not an air leak at all. A glass unit whose seal has failed no longer insulates properly. You will usually see misting or condensation between the panes that cannot be wiped away. The door may feel cold to the touch near the glass and radiate chill into the room even when no air is moving.

In these cases, adding strips to the frame will not help. The fix is to replace the glass unit, not the whole door. Where the frame is sound, a glass-only replacement keeps the door you have, fits new sealed units to the existing frame, and avoids the disruption of removing the whole door set.

This also has a regulatory advantage. Building Control guidance from Hampshire says that replacing only the glass unit of a patio door does not require Building Regulations approval, whereas replacing the whole door or frame must comply with Part L. That means using an installer registered with a competent person scheme such as FENSA or CERTASS, or applying to Building Control. Always check the rules for your own property with your local authority, as requirements can differ.

We offer double glazed door repairs that include glass replacement for patio and French doors, and our guide to French door glass replacement explains why keeping the frame can make sense.

Keep your trickle vents open

Stopping draughts is not the same as sealing a home airtight. The Energy Saving Trust is clear that draught proofing is aimed at uncontrolled air leaks, and that homes need background ventilation, such as trickle vents and wall vents, to keep air quality healthy and prevent damp.

• Never block or seal trickle vents on the door or frame, even if you feel a slight breeze through them.
• If your home is already fairly well sealed, speak to a professional before adding more draught proofing.
• If you see heavy condensation on the inside of the glass or walls, it may be an indoor moisture problem and not a failed door seal.

Our view: repair the part that has failed

Our view at Cloudy2Clear Windows.

Since 2005 we have been installing, replacing and repairing double glazed windows and doors for homes and businesses. In that time, the pattern we see most often is a door that is perfectly serviceable but has one failed part: a tired seal, a worn hinge, a sagging roller, or a misted glass unit. We think replacing the whole door is usually the wrong first step.

If the frame is sound, replacing just the glass or the failed component restores comfort with less disruption, less waste and a shorter wait. It is also in line with council guidance that repair is often the more sustainable option where an existing door is structurally sound. We offer a 25-year guarantee.

Not every draught needs us. A worn compression strip or a dirty track is something a careful homeowner can sort out in an afternoon. We can help where the draught has more than one cause, or where the glass, hinges and locking points all show wear together.

Upgrading the glass while you are at it

Once your door is sealed and aligned, upgrading the glass can improve comfort further. We can fit soundproofing glass units and insulated glass in your existing frames. The Energy Saving Trust’s page on energy efficient windows and doors gives a range of options from simple upgrades to full replacement, so you can see where glass upgrades fit.

Need a hand with your patio door?

If you have run through the checks and the draught remains, or you can see misting in the glass, we can help. Cloudy2Clear Windows repairs and replaces the glass in patio doors across the UK, keeping your existing frame wherever it is sound. See our double glazed door repairs page or visit our home page to get in touch. Our phone lines are open Monday to Friday, 8:30am to 6:30pm.

Our guide on what causes a window draught has more detail.

Frequently asked questions

How do I draught proof a uPVC patio door?

Start by checking the rubber gaskets for splits or flattening, and replace any that have worn. Then check the hinge or roller alignment. Keep trickle vents open.

What can I put on my patio doors to stop draughts?

Brush strips suit sliding doors and bottom gaps, while compression strips suit hinged doors with consistent gaps. Gaskets are best for modern uPVC and aluminium frames.

My patio door is misaligned. How can I fix it?

Hinged doors can often be adjusted at the hinges with an Allen key, and sliding doors usually have adjustment screws on the rollers. If the door still drops, rubs or will not lock firmly, worn hinges, rollers or locking points probably need replacing.

Do I need Building Regulations approval to replace the glass in a patio door?

According to Hampshire’s Building Control Partnership, replacing only the glass unit does not need approval, but replacing the whole door or frame does. Check with your local authority for your own property.

Sources

• Draught proofing, Energy Saving Trust
• Five things to prepare your home for winter, Energy Saving Trust
• Energy efficient windows and doors, Energy Saving Trust
• Replacement windows and doors, Building Control Partnership
• Energy efficiency retrofitting SPD, Bath and North East Somerset Council
• Repair or replacement of doors and windows, St Albans council

If your VELUX roof window has misted glass, a cracked pane or a draughty, noisy feel, you can often upgrade the sealed glass unit without replacing the whole window. That means a shorter visit, less disruption and no change to your roof opening. This guide explains when a glass-only upgrade is the right call, what to check before you book, and when a full window replacement is the better route.

What a VELUX glass upgrade actually involves

A roof window is made of a frame, a sash that opens, and a sealed double glazed unit set into the sash. The glass upgrade swaps that sealed unit for a new one, ideally with better insulation or sound performance, while the frame, flashing and roof covering stay where they are.

The sealed unit is two or more panes held apart by a spacer bar, with a gas or air gap between them. When the seal breaks, moist air gets in and you see condensation or a milky haze between the panes. The unit has failed and needs replacing.

Common reasons people upgrade the glass:

• Misting or fogging between the panes, which means the seal has failed.
• Cracked or chipped glass from hail, a falling branch or a knock during loft work.
• Cold spots and draughts from an older, lower-performing unit.
• Noise from rain, traffic or aircraft, which is far more noticeable through a sloping roof window.

If you are not sure whether your problem is the glass or something else, our guide on how to know if your Velux window needs replacing walks through the signs.

Glass only or the whole window?

This is the question most readers have, and the honest answer is that it depends on the age and condition of the window as a whole.

VELUX says a roof window typically lasts 20 to 30 years, after which seals often fail, leading to leaks, constant condensation and reduced energy efficiency. The same page lists persistent draughts, discoloured or broken glass and moisture around the frame as signs it is time to act.

The pattern is simple. If the frame, hinges and flashing are in good order, new glass gives you most of the benefit with the least upheaval. If the frame itself is failing, new glass in a failing frame is a short-term fix, and we will tell you so.

Check the details before you order anything

VELUX has changed its product dimensions and mounting systems over the decades, so assuming a standard size is how people end up with a unit that does not fit.

1. Find the data plate. VELUX describes it as a label with the exact product information, and its guidance on finding the data plate explains where it sits on different products. On many windows it is behind the ventilation flap.
2. Note the production code. The code tells you the size and the era of manufacture.
3. Check the age. Windows made before 2001 often have a thinner sealed unit than later ones. Some modern units need an adaptor or conversion arrangement to fit an older sash, which is one reason a survey beats guesswork.
4. Look at the condition of the sash and seals. Perished rubber seals or damaged flashing should be fixed during the same visit.

You can see how we approach these jobs on our VELUX window repair page.

Choosing the right glass specification

Upgrading is the moment to choose better glass, rather than simply copying what failed. These are the choices that matter.

Insulation and low-emissivity coatings

A low-emissivity coating reflects heat back into the room in winter and helps limit solar heat gain in summer. Combined with a sealed gap filled with a low-conductivity gas, it can transform a cold loft room. Our guide to window U-values explains the rating in plain English: the lower the figure, the less heat escapes.

Warm edge spacers

The spacer bar around the edge of the unit matters more than most people expect. The Rooflight Association’s specification guide for glass rooflights recommends warm edge spacers because they reduce thermal bridging compared with traditional aluminium spacers, a common cause of condensation at the very edge of the pane. Ask any installer, including us, what spacer is in the quoted unit.

Laminated and acoustic glass

Laminated glass has a plastic interlayer bonded between glass layers. It holds together if broken, which is a safety benefit overhead, and it dampens sound. VELUX notes that triple-layer glazing can reduce external noise for homes near busy roads or flight paths while also improving thermal insulation. If noise is your main problem, read about our soundproofing and noise reduction glass.

Insulated glass in general

Our insulated glass service covers sealed units built for energy efficiency.

Building Regulations: what to know in England

Replacing glass is not always treated the same as replacing a whole window, so check before work starts. In England, Building Regulations require replacement windows, including roof windows, to meet set thermal performance standards. For existing dwellings, a replacement roof window typically needs a maximum U-value of 1.4 W/m²K. You can show compliance by using an installer registered with a Competent Person Scheme such as FENSA or CERTASS, or by submitting a Building Notice to your local authority building control.

The Rooflight Association’s quick guide to the approved document notes that roof window limiting U-values depend on the circumstances of the installation, so the figure above is a starting point, not a universal answer. Your installer or building control team should confirm which one applies to your project.

Two further points:

• Scotland, Wales and Northern Ireland have their own building standards. The England figures above should not be assumed to apply there. If you are in Scotland, ask your installer or local authority which standard applies.
• Commercial and housing association premises often face stricter fire safety and escape route requirements. The same Hampshire guidance reminds owners that using a registered competent person or a professional glazing service helps ensure the Building Regulations certificate and other paperwork is filed correctly, avoiding legal or insurance problems later. See also our Building Regulations guide for windows.

Our view: why we replace the glass, not the frame

At Cloudy2Clear Windows we have repaired and replaced double glazing for homes and businesses since 2005, and one lesson has held every year: most people call us about a symptom, not a full-window problem. A misted pane or a cracked unit is a glass problem, and treating it as one means a shorter visit, less mess and a smaller job on your roof.

We replace only the glass, not the frame, which keeps disruption down and gets you back to a clear, efficient window faster. But we are straight with customers about the limits. If the frame is rotten or the window leaks around the edges, we say so, because glass in a failing frame will not give you a result you will be happy with in five years.

We also encourage people to treat a glass repair as a chance to improve. You are already having the unit replaced, so the better specification, whether that is improved insulation, acoustic laminated glass or warm edge spacers, is a small step from there. Our glass comes with a 25-year guarantee.

Planning the work around the rest of your roof

A glass upgrade is a good moment to look at the roof around the window. Flashing, tiles and sealant near the window affect whether new glass stays dry and efficient. If your roof is ageing generally, this overview of roof upgrade ideas for homeowners is a helpful way of thinking about which improvements are worth doing first. It focuses on Florida shingle roofs, so the materials differ from most UK roofs, but the idea of ranking repairs by payoff applies anywhere.

VELUX states that replacing a whole roof window can often be done in as little as four hours from inside the room, with no structural changes. A glass-only visit is typically less involved, and we confirm timing once we have seen your window.

Before the visit:

1. Clear the area under the window and protect furniture and flooring.
2. Make sure we can reach the window safely from inside.
3. Have the data plate photo or production code ready.
4. Tell us about any leaks, stains or draughts you have noticed.

Homes, landlords and commercial buildings

Our customers include homeowners, small businesses and housing associations, and the same principles apply to each, with a few extra considerations.

• Homeowners: focus on comfort, noise and condensation. Choose a specification for the room’s use, such as a bedroom that needs quiet or a loft office that overheats.
• Landlords and housing associations: keep records. Record the window’s code, the specification fitted and any certificate issued, so later inspections are simple. Our inspection and full replacement service is built for this kind of portfolio work.
• Businesses: roof windows over offices, stairwells and shared spaces can have safety and escape implications. Our commercial window repair team can advise. Our article on window safety for businesses includes a compliance checklist.

Book a VELUX glass upgrade with Cloudy2Clear Windows

We replace failed, misted and cracked glass units in VELUX and other roof windows, along with conservatory, commercial, door and caravan glass, and we cover the UK through local branches. Our lines are open Monday to Friday, 8:30am to 6:30pm. Start with our VELUX window repair service, or browse all our services to see what else we can do on the same visit.

Frequently asked questions

Can you replace just the glass in a VELUX window?

Yes, in most cases where the frame and sash are sound. The sealed unit is swapped for a new one that matches your window’s production code, and the frame stays in place. If the frame is damaged, a full replacement may be the better option.

How long does a VELUX roof window last?

VELUX gives a typical lifespan of 20 to 30 years. After that, seals often fail, which leads to leaks, condensation and poorer energy efficiency. Well-maintained windows can do better, while neglected ones may need attention sooner.

Is it better to replace the whole window or just the glass?

If the frame is in good order, glass alone usually gives you the improvement you want with less disruption. If the window is near the end of its life, or you want a larger glazed area or electric operation, a full replacement can offer better long-term value. We will give you an honest view once we have inspected it.

Do I need Building Regulations approval for new roof window glass?

In England, replacement windows including roof windows must meet thermal standards, and compliance is shown through a competent person scheme installer or a Building Notice. Rules differ in Scotland, Wales and Northern Ireland, so ask your installer which applies to your property.

Sources

• VELUX: things to consider when replacing roof windows
• VELUX: Replacement Supply & Fit service
• Building Control Partnership Hampshire: replacement windows and doors
• Rooflight Association: glass rooflights specification guide
• Rooflight Association: approved document quick guide