Suffering from blown windows in your home? Getting them repaired can be a lot more straightforward than you might think. Here, we’ll explore how much blown window repair typically costs.

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If you've spotted that familiar milky haze between your window panes, you're probably dealing with a blown window.

It's one of the most common double glazing problems in UK homes - and the good news is that in most cases you won't need to replace the whole window, just the glass unit inside it.

This guide covers everything you need to know: what blown windows actually are, how much repairs cost, what affects the price, and how to find a vetted window repair specialist near you.

How much does blown window repair cost in 2026?

Blown window repair cost typically ranges from £55 for a single pane up to £600 for a large whole-window replacement.

The exact price depends on whether you need a single pane replaced or the entire glazed unit, plus the size and type of window involved.

Single pane blown window repair cost

If only one pane of glass is affected, you may be able to replace just that pane rather than the whole unit. This is the most cost-effective option when the damage is limited.

To summarise what you can expect to pay per pane:

• A 200mm x 400mm pane costs around £55

• A 500mm x 700mm pane costs around £74

• An 800mm x 1,000mm pane costs around £117

• A 900mm x 1,200mm pane costs around £145

Whole blown window repair cost

If the entire glazed unit has failed, you'll need a full unit replacement.

The frame can usually stay - it's just the glass unit that's swapped out, which keeps costs significantly lower than a full window replacement.

n.b. Based on Checkatrade data. Costs are estimates - get a local tradesperson to quote for your specific job.

• A small blown window replacement costs around £100 to £200

• A standard window costs around £200 to £325

• A large blown window can cost £350 to £850

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Additional costs for blown window repair

There are a few extra costs worth factoring in when budgeting for blown window repair. Some of these may be included in your quote - always ask upfront.

Your window repair may uncover other work that needs doing. At Checkatrade, you can find checked and reviewed window fitters, builders, plasterers, carpenters, and more - all in one place, all committed to quality and a job done right.

What is a blown window?

A blown window happens when the airtight seal around your double (or triple) glazed unit fails.

Once that seal goes, the insulating gas - usually Argon - escapes, and moist air gets in between the panes. That's what causes the milky, foggy, or misty appearance you can't wipe away.

It's important to understand that once a unit is blown, the moisture inside cannot be cleared. The glass unit needs to be replaced - but in the vast majority of cases, you can keep your existing window frame, which keeps the cost well below a full window replacement.

Signs your window is blown

• Misting, fogging, or water droplets between the panes that can't be wiped from either side

• A cloudy or milky appearance even after cleaning

• Visible water pooling at the bottom of the spacer bar inside the glass

• Draughts around the window frame

• Windows that are stiff or difficult to open

• Higher-than-usual energy bills

• Increased noise from outside

What causes blown windows?

Blown windows are usually caused by a gradual breakdown of the perimeter seal around the glazed unit. Common causes include:

• Poor installation - if the window wasn't fitted correctly, gaps can form that put pressure on the seal over time

• General wear and tear - seals naturally degrade over years of use, particularly on older windows

• Accidental damage - impact or stress on the glass can weaken the seal

• Harsh cleaning chemicals - certain products can erode the rubber seal around the unit

• Extreme temperature changes - repeated expansion and contraction of the frame can stress the seal over time

A blown window can also be a sign that the glass itself has weakened, which may be a security concern worth raising with your tradesperson.

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Factors affecting blown window repair costs

Several things will influence the final price you pay for blown window repair:

• Size and style of window - larger windows and those with more panes, such as bay windows, cost more to repair. Specialist window types like sash, tilt-and-turn, and casement windows may also be more complex to work on

• Extent of the damage - a single affected pane will cost less than multiple panes or a fully failed unit

• Type of glazing - toughened, frosted, self-cleaning, or decorative glass costs more than standard clear glass. Triple glazing costs more than double glazing

• Additional prep work - if the frame is damaged or structural repairs are needed, costs will rise

• Accessibility - difficult-to-reach windows on upper floors or in awkward positions add to labour time and cost

• Where you live - labour rates vary across the UK, with higher rates in London and the South East

Blown window repair vs full window replacement

In most cases, you won't need to replace the whole window - just the glazed unit inside it. This can save up to 70% compared to full window replacement.

That said, a full replacement may make more sense if:

• The window frame is structurally damaged, warped, or soft

• Your windows are over 15 years old and showing multiple signs of deterioration

• The windows are difficult to open or close properly

• You want to upgrade the style or energy efficiency rating

• Repairs would only provide a short-term fix given the overall condition

If you're on the fence, a vetted glazier can inspect your windows and give you an honest assessment of whether repair or replacement is the better long-term investment.

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Can you fix a blown window yourself?

Replacing a double glazed unit requires specialist tools, precise measurements, and technical knowledge of how sealed units are manufactured and fitted.

It's not a job that lends itself to DIY - an incorrectly fitted unit will fail quickly and could create further problems with damp or draughts.

It's also worth noting that any work affecting your home's glazing should comply with building regulations. Hiring a FENSA-registered professional ensures the work is certified and compliant - which matters when it comes to selling your home.

How to prevent blown windows

You can't prevent a window seal from failing forever, but these steps will help extend its life:

• Check the sealant and caulking around your windows regularly for cracks or gaps

• Fill any small gaps with silicone sealant - or have a professional do it

• Clean your windows at least every six months to prevent debris build-up around the seal

• Avoid harsh cleaning chemicals, particularly solvent-based products

• Make sure windows are properly ventilated to reduce the condensation that stresses seals over time

• If you're having new windows fitted, use a FENSA-registered installer to ensure the job is done correctly from the start

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How to find a blown window repair specialist

Finding the right tradesperson matters. Blown window repair requires specific glazing knowledge - not just general building skills.

At Checkatrade, every window repair specialist on our platform has been through up to 12 checks before they can list with us - including ID verification, insurance checks, and qualification checks.

You can also read genuine reviews from real customers before making your decision.

When you contact a tradesperson, it's worth asking:

• Are you FENSA-registered?

• Will you inspect the windows before quoting?

• Does your quote include removal and disposal of the old unit?

• What guarantee do you offer on the work?

• Is VAT included in the price?

Book your repair sooner rather than later. A blown window won't fix itself - and the longer it's left, the greater the risk of damp, mould, and heat loss building up around the affected frame.

Every Checkatrade job is backed by our £1,000 guarantee

Up to £1000. Eligibility criteria and T&C’s apply.

Blown window repair cost: checklist

Blown window repair checklist

• Check all windows for condensation or misting between the panes

• Note the size and number of affected windows before getting quotes

• Check whether your home insurance policy covers blown double glazing

• Get at least three quotes from vetted window repair specialists

• Ask whether you need a single pane replacement or a full unit replacement

• Confirm your tradesperson is FENSA-registered

• Ask for a written quote that itemises labour and materials separately

• Book sooner rather than later to avoid damp, heat loss, and higher energy bills

Blown window repair cost FAQs

What are the signs of a blown window?

The main sign is condensation or misting between the panes that can't be wiped away from either side. Other signs include a cloudy or milky appearance, visible water pooling inside the unit, draughts around the frame, windows that are stiff to open, and unexpectedly higher energy bills.

How do I know if my double glazing is blown?

If the condensation is trapped between the two panes of glass - not on the room-facing surface and not on the outside - the sealed unit has failed. You can test this by trying to wipe the glass on both sides. If the mist remains, the unit is blown.

Can you repair a blown window, or does it need replacing?

The glass unit itself cannot be repaired once blown - the moisture inside is permanent. However, in most cases only the glazed unit needs replacing, not the whole window. Your existing frame can usually be kept, which significantly reduces the cost.

How long does it take to repair a blown window?

Replacing a single blown double glazed unit typically takes between one and three hours. If you have multiple windows to repair, your tradesperson may spread the work across more than one visit.

Is blown double glazing covered by home insurance?

This depends on your specific policy. Most standard home insurance policies won't cover blown windows if the cause is general wear and tear or seal failure, unless you have specific accidental damage cover. It's worth checking your policy documents or calling your insurer before arranging repairs.

Will a blown window affect my energy bills?

Yes. Once a glazed unit is blown, it loses its insulating properties - the Argon gas between the panes that prevents heat transfer has escaped. This means your home loses heat more quickly, your heating system works harder, and your energy bills rise. Repairing blown windows as soon as possible is one of the most straightforward ways to improve your home's energy efficiency.

Can blown windows cause damp?

Yes, indirectly. A blown window often allows draughts in around the frame, which can cause moisture to build up on surrounding surfaces - particularly on window sills, walls, and plasterwork nearby. If you've noticed damp patches near your windows, a blown unit may be a contributing factor.

Should I repair or replace misted double glazing?

Some companies advertise a "mist removal" service, but this is generally not a long-term fix - it doesn't restore the insulating properties of the unit. The most effective solution is to replace the glazed unit entirely. Remember, in most cases the frame stays in place, so it's far cheaper than replacing the whole window.

How much does blown window repair cost in the UK?

On average, repairing a blown window costs between Single pane blown window repair costs: B3 for a single small pane and Whole blown window repair costs: D5 for a whole large window replacement. The exact cost will depend on the window size, glazing type, number of panes affected, and your location.

Can I fix a blown window myself?

It's not recommended. Replacing a double glazed unit correctly requires specialist tools and precise measurements, and the work needs to meet building regulations. Incorrectly fitted units will fail quickly and could introduce new damp and draught problems. Always use a FENSA-registered professional.

Should you repair or replace windows?

Our experts know everything there is to know about whether you need to replace or restore your windows, signs to looks out for, and costs associated with each option.

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Related guides

If you need other window or glazing work carried out, these guides may help:

• Double glazing cost guide

• Window glass replacement cost

• Window fitting cost

• Window frame repair cost

• Window seal replacement cost

• Cost of replacing misted double glazing units

• Triple glazing cost

• New windows cost guide

• Window hinge repair cost

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