What the job involves
A misted window is a double-glazed unit whose perimeter seal has failed. Moist air has got into the gap between the two panes, and the drying agent in the spacer bar has become saturated. The result is the cloudy film, droplets or watermarks that you can't wipe off because they are between the sheets of glass, not on the surface.
In most cases the frame is fine and only the sealed glass unit needs replacing. A fitter measures the existing unit, orders a new one made to size, then removes the beads or gaskets that hold the glass, lifts out the old unit, sets the new one on packers and refits the beading or seals. The job is much smaller than replacing whole windows, and it is usually cheaper per opening. It also means the frames, handles, hinges and decoration stay as they are.
This guide covers the usual scope of one to three units. That might be a single patio door pane, a bedroom window and a bathroom window, or the same type of unit in several rooms.
One caution: companies that offer to clear the mist by drilling the glass and cleaning it out can improve the look, but the seal and insulating gas are still gone. Replacement is the proper fix if you want the window to perform as it should.
What affects the price
- Size of the unit. Larger panes use more glass and are heavier, so they cost more to make and need more people to handle safely. A big patio door or picture window costs noticeably more than a small side light.
- Number of units. Fitting several units in one visit spreads the travel and set-up time, so the cost per unit usually falls. Even so, a single unit still carries the cost of a visit and a made-to-measure order.
- Type of glass. Standard clear units are the cheapest. Obscure or patterned glass, laminated glass, toughened glass, tinted or solar-control glass and acoustic glass all add cost. Safety glass is required in some places, such as doors and low-level panes next to them, so check what your window needs.
- Specification of the new unit. Energy-efficient coatings, warm-edge spacers and gas filling are common now. A better specification costs a little more but is usually worth having, especially if you are replacing only a few units and want them to match the rest.
- Decorative features. Leaded lights, Georgian bars, astragal bars or bespoke shapes such as arches and circles take longer to make and need specialist fitting.
- Frame type and condition. Modern PVC-U frames are usually straightforward. Timber, aluminium and older frames can need more care, and rotten beads, tired gaskets or damaged rebates may need repair before new glass goes in.
- Access. Ground-floor windows are easy. Upper-floor windows, awkward stairwell windows or conservatories and roof glazing can mean ladders, extra labour, scaffolding or glass-lifting equipment.
- Location. Labour rates and travel time vary across the UK, and some areas have fewer specialist suppliers.
- Extras. Trickle vents, new seals, new handles, resealing, disposal of the old glass and making good all count towards the final figure, whether or not they are itemised.
The prices on this page show what other homeowners paid for similar jobs, which is a useful reference point when your own quote comes in.
Ways to keep the cost down
- Bundle the work. If several windows are misting or starting to fail, have them all done in one visit. Ask the fitter to look over the rest of the house while on site.
- Measure and check before calling. Note which units are misted, roughly how large they are, whether the glass is obscure or patterned, and which floor they are on. A fitter can quote more accurately from clear photos.
- Keep the spec sensible. Match what you have unless you want an upgrade. Paying for features you don't need, such as acoustic or tinted glass, adds cost for little benefit.
- Check for a guarantee. Some glazing, particularly newer installations, comes with a guarantee against seal failure. Look through your paperwork or ask the original installer before paying for a new unit.
- Get several quotes. Obtain at least three, from a local glazier and a window company, and compare like for like.
- Don't delay too long. Once a seal has failed the unit will not recover. Leaving it won't normally damage the frame, but if the cause is a cracked pane or a rotting frame, it can get worse.
- Be flexible on timing. Fitters may offer a better arrangement if you can take a slot that suits their schedule.
What should be included in a quote
A decent quote is written down and specific. Check that it covers:
- [ ] The number of units and their sizes, ideally with the location of each.
- [ ] The glass specification: clear, obscure, toughened or laminated, coating, gas fill and spacer type.
- [ ] Whether the new units match the existing ones, including any bars or leaded details.
- [ ] Supply and fitting of the units, with VAT shown if it applies.
- [ ] Replacement of beads, gaskets or seals where needed.
- [ ] Removal and disposal of the old glass.
- [ ] Access arrangements, including any ladders or scaffolding, and whether they are charged.
- [ ] Any repair to the frame, or a clear statement that none is included.
- [ ] The guarantee on the new units and on the workmanship, in writing.
- [ ] Lead time for manufacture, and the likely fitting date.
- [ ] Payment terms, including any deposit and when the balance is due.
- [ ] Whether the fitter will clean the glass and leave the area tidy.
Questions to ask a window fitter
- Is the frame in good enough condition to take a new unit, or will it need repair?
- Will you measure the units yourself, rather than relying on my measurements?
- Does the glass need to be toughened or laminated for safety reasons at this location?
- Can you match the existing glass, including the pattern, bars or colour?
- What spacer bar and gas fill will the new units have?
- What guarantee do you give, and who honours it if you stop trading?
- Will you tell me how long you have been trading and show me recent similar work?
- What happens if the unit arrives the wrong size?
- Are there any extras that could be added to the price after you start?
How long it takes and what to expect
The slowest part is manufacture. Units are made to measure, so expect a wait between the survey and the fitting. That is normal and should be explained up front. Rush orders are sometimes possible, but may cost more.
On the day, fitting one to three standard units is usually a matter of hours rather than days. Expect some noise, some dust around the frame and a fitter coming in and out of the room. Move furniture and curtains away from the window, and clear access to the outside if the work is done from there.
When the work is done, check that the new unit is clean, free of scratches, sits squarely and the window opens and closes as before. Check that the seals and beads are neat, and that there is no gap or draught around the glass. Keep the paperwork and guarantee somewhere safe. New units can sometimes show slight condensation on the outside surface in cold, damp weather. That is not a fault and is a sign the glass is insulating well.
Signs a quote is too cheap or too expensive
Too cheap
- No clear specification of the glass, so you can't tell what you are getting.
- No mention of a guarantee, or one that is vague and unwritten.
- A fitter who wants full payment in cash upfront before ordering.
- Pressure to decide on the spot, or a price that is only "good today".
- No itemisation for disposal, beads, seals or VAT, which suggests extras to come.
- A suggestion that drilling and cleaning will do the same job as replacement.
Too expensive
- A price far above other quotes for the same specification and no clear reason, such as difficult access or bespoke glass.
- Fitting costs that seem to be loaded on top of an already high glass price.
- Upgrades, such as acoustic or solar-control glass, included without you asking.
- Vague extras added late, such as "access charges" that were not mentioned at the survey.
- A quote for replacing the whole window when only the glass unit has failed and the frame is sound.
If a quote looks out of line either way, ask the fitter to explain it. A good tradesperson can tell you exactly what each part of the price covers.