Quick answer: New-build glass carries abrasive brick and plaster dust, mortar splash, paint specks and sticker adhesive — so the cardinal rule is soak first, never dry-wipe, and be very careful with blades. Flood the glass, let plaster and mortar soften, wash with plenty of water, and lift paint specks with a plastic scraper or solvent rather than steel. Modern coated glass scratches more easily than old float glass, and developers' warranties routinely exclude scratched glass — which is why "the builders' clean did it" arguments end badly. Deep-clean once, properly; then maintenance is easy.
Congratulations on the new house. Now look at the windows in low sun: that film you assumed was normal dust is a cocktail of plaster, cement, brick dust and decorator's overspray — some of it gently bonded to the glass, all of it abrasive. New-build glass needs one careful restoration clean, and it needs it done right, because the mistakes are permanent.
Why new-build glass is a scratch trap
Construction dust is not house dust: brick, plaster and cement particles are hard and angular, and any dry wipe drags them across the pane like fine sandpaper. Worse, snagging inspections find scratched glass constantly, and the usual cause is exactly this — someone (builder or owner) wiping dusty glass with a dry cloth. First rule of the whole job: water first, always, everywhere.
Step 1: flood and soak
Hose the glass generously, or sponge-flood it indoors. Let it sit wet for several minutes: plaster and mortar splash are lime-based and soften with water. Re-wet as needed. Most of the "stubborn" material on new glass gives up to patience here — resist the urge to pick at anything dry.
Step 2: wash heavy, rinse heavier
Warm water with a squirt of washing-up liquid, a soft non-scratch sponge and light pressure. You're floating dust off, not scrubbing it off. Rinse until the run-off is clean — then a final pass with vinegar solution or purified water strips the soap film so you don't spend your first year fighting mystery streaks.
Step 3: the specks (paint, mortar, stickers)
- Paint specks: soften water-based paint with a wet cloth held on the spot; lift with a plastic scraper at a shallow angle. Solvent (white spirit on a cloth) for gloss overspray — spot-test frame gaskets first.
- Mortar dots: keep soaking; they release whole. Never chisel.
- Sticker adhesive: peel labels wet; residue lifts with a little cooking oil or citrus remover, then re-wash the area.
- Blades: professionals use them, on bare wet glass, at 30 degrees, new blade every window — and even they scratch coated glass sometimes. If your glass has any surface coating (many modern energy-efficient units do), a blade can leave permanent hairline arcs. If in doubt, soak longer instead.
Step 4: check before you sign anything
Do this clean (or a professional builders' clean) before your snagging window closes — scratched or etched panes, failed seals and debris inside the glazing unit only become visible on clean glass, and they're the developer's problem only while snagging is open. Photograph anything you find, against low-angle light.
After the reset: keep it boring
Once the construction load is off, new-build windows are the easiest glass you'll ever maintain — big modern panes, good coatings, fresh seals. That's robot territory: a CleanBot R1 keeps every pane, including the upstairs ones you'd otherwise ladder, at show-home standard from here on. Just never send any robot (or cloth) across gritty glass — that pre-rinse rule is permanent.
FAQ
The site offers a "sparkle clean" — is my job done?
Sparkle cleans are fast and cosmetic; check the glass in low sun anyway, especially corners and outside faces. Assume nothing until you've seen it clean and dry.
There's dust between the panes — can I clean it?
No — that's inside the sealed unit, which means the unit failed or was assembled dirty. Snag it; the unit gets replaced. (Same story as misting between panes.)
How soon can I clean after handover?
Immediately for glass. Give painted frames and sealants a few weeks to cure before anything stronger than water goes near them.
One careful weekend now, and your new-build's glass starts its life actually new — then let the robot keep it that way.