You’ve just picked up the keys. The carpets are fresh, the paintwork is spotless, and everything smells like a show home. The last thing on your mind is booking a window cleaner. The place is brand new — how dirty can the windows actually be?
Quite dirty, as it turns out. And the type of dirt left behind on new build windows isn’t the kind you can sort out with a cloth and a spray bottle on a Saturday morning. It’s construction contamination. It behaves differently, it damages glass differently, and if it’s left too long, it stops being a cleaning problem and starts being a glazing problem.
What’s Actually on Your Windows
Newly built windows look clean from a distance. Up close, and in the right light, it’s a different story.
During construction, your windows were present for all of it, the plastering, the rendering, the painting, the cement work, the drilling, the sanding. Every trade that came through the property left something behind. Most of it settled on the glass.
Here’s what’s typically found on new build windows after construction:
- Cement and mortar splatter – small spots and runs that dry hard onto the glass and frames
- Silicone smears – from sealant work around frames, which smear badly if touched before curing and leave a greasy residue
- Paint spots – overspray or splatter from internal and external decoration
- Plaster dust – ultra-fine particles that settle across every surface, including glass, and form a film when they get wet
- Self-adhesive label residue – most new windows are fitted with protective film or stickers that leave a sticky residue when removed
- Render and masonry dust – from external brickwork and render, which becomes alkaline when wet and can etch glass over time
- Sawdust and wood particles – from first-fix and second-fix carpentry work throughout the property
None of this is the developer’s fault. It’s simply the reality of having windows installed early in the build process and then exposed to months of construction activity. By the time you move in, the glass has been through a lot.
Why This Contamination Is Different
Regular household dirt, dust, rain, fingerprints, sits on top of glass. It’s surface contamination. Clean it properly and it comes away.
Construction contamination is different. Some of it bonds chemically with the glass surface. Some of it hardens into deposits that require careful mechanical removal. Treat it like ordinary dirt and you risk spreading it further, scratching the glass, or making it harder to remove.
Cement and mortar are a particular concern. Both are alkaline. Glass, at a microscopic level, is vulnerable to alkaline substances, particularly when they’re left in contact with the surface for extended periods. This process, known as alkaline etching, can leave permanent marks on the glass that no amount of cleaning will fix. The glass itself has been altered.
How long does it take for this to become a problem? It depends on the product and the conditions, but many glazing specialists suggest that cement and mortar splatter left on glass for more than a few weeks in damp conditions can begin to cause surface damage. That’s not a long window and most new build owners aren’t thinking about their windows in the first weeks after moving in.
The Protective Film Problem
Most new windows are delivered and fitted with a protective film on the glass, a thin plastic or adhesive layer designed to protect the glass during transit and installation. In theory, this film is removed before or shortly after the build is complete. In practice, it isn’t always done thoroughly, and remnants are commonly left behind.
Here’s where it becomes a problem. Adhesive protective film that is left on glass and exposed to heat, particularly summer sun, bonds more aggressively to the surface over time. What should peel away cleanly becomes increasingly difficult to remove. Left long enough, it can leave a permanent adhesive residue that distorts the glass visually.
If you move into your new build and notice patches of haze or slight distortion on the glass, particularly around the edges, this is likely film residue. Don’t try to scrape it off yourself. A professional cleaner with the right tools and products can remove it safely. Attempting it with a blade or abrasive cloth risks scratching the glass and creating a much more expensive problem.
What Developers Are and Aren’t Responsible For
Most new build developers carry out a basic clean of the property before handover. This typically covers internal surfaces, floors, kitchen units, bathroom fittings, and general dust removal. Window cleaning, particularly external, is often done to a minimal standard if it’s done at all.
It’s worth checking your handover documentation carefully. Some developers include a professional window clean as part of their snagging process. Many don’t. And even when they do, it may have been completed weeks before your move-in date, leaving time for dust and debris from final trades to settle back on the glass.
Ask your developer or site manager directly: when were the windows last cleaned, and what did that clean include? Were the frames cleaned as well as the glass? Were the external windows included? You may find the answer is less thorough than you assumed.
The Snagging Window
If you’re within the first two years of owning a new build, you’re likely still within your developer’s snagging warranty period. This is important, because it affects how you approach any damage you discover.
If construction contamination has already etched or damaged your glass, you may have a snagging claim, but only if the damage is identified and reported within the warranty period. Glass that has been visibly etched or scratched during construction is a defect. It should have been addressed before handover.
Document everything. If you notice haze, etching, scratches, or residue on your windows that you can’t explain, photograph it clearly and report it to your developer in writing before attempting any cleaning yourself. Once you’ve cleaned the windows, even professionally, it can be harder to argue that the damage was pre-existing.
This is another reason to get a professional eye on your windows early. A good window cleaner will identify damage that isn’t cleanable and advise you to raise it as a snagging issue rather than attempting to clean through it.
New Frames Need Attention Too
It’s not just the glass. New PVCu window frames, the white or cream frames fitted in the majority of new builds, arrive from the factory clean and bright. They don’t stay that way through months of construction.
Cement, render, and paint spots affect frames just as much as glass. So does silicone sealant smear, which is particularly common around the joints where frames meet the surrounding brickwork. Left on white PVCu, these marks become harder to remove over time as the frame weathers and the contaminants set.
Plaster dust is another issue. It settles into the gaskets, seals, and drainage channels of window frames, the small recessed areas that most people never clean. These channels are designed to drain water away from the frame. When they’re blocked with construction debris, water can back up inside the frame, potentially causing issues with seals and the longevity of the unit.
A professional clean that includes the frames, seals, and drainage channels isn’t just about appearance. It’s basic maintenance that protects the lifespan of the windows themselves.
How Soon Is Soon Enough?
There’s no fixed rule, but most window cleaning professionals who work with new build properties suggest booking a clean within the first four to six weeks of moving in. This is early enough to remove construction contamination before it has time to cause surface damage, but late enough that the final trades have finished and won’t be adding more debris to freshly cleaned glass.
If you’ve already been in your new build for several months and haven’t had the windows professionally cleaned, book one as soon as possibl, particularly if:
- You’ve noticed haze or residue on the glass that doesn’t wipe away
- Your frames have visible spots or smears from construction
- You’re approaching the end of your snagging warranty period
- The property went through summer without the windows being cleaned
What a Professional Clean Involves
A professional window clean on a new build is more involved than a standard domestic clean. It should include:
- Safe removal of cement and mortar splatter using appropriate tools and chemicals that won’t scratch the glass
- Adhesive residue removal from protective film and stickers
- Silicone smear treatment using specialist products
- Frame, seal, and drainage channel cleaning to remove construction dust and debris
- Final glass clean using purified water for a streak-free finish
Make sure you discuss the new build context when you book. Not every window cleaner carries the specialist products needed for construction contamination. A cleaner who turns up expecting a standard domestic job may not have what’s needed to deal with cement splatter or adhesive residue safely.
The Cost of Waiting
A professional new build window clean typically costs between £80 and £200 depending on property size and the level of contamination. That’s a straightforward, one-off cost.
Etched glass panels on a new build can cost anywhere from £150 to £500 or more per unit to replace and that’s assuming the damage is caught within the snagging period. Outside of warranty, the cost falls entirely on you.
The maths are simple. The risk of waiting isn’t.
Your new home deserves to be seen clearly, through clean, undamaged glass that lets in every bit of light the property has to offer. Don’t wait until the damage is done to start thinking about it.
