Flagship guide · Method
The best way to clean windows
One method covers almost every domestic pane, inside and out: wet the glass thoroughly, work the soil loose, take the water off in overlapping squeegee strokes, and dry the edges with a clean cloth. Everything else in this guide is about doing those four steps in the right order, in the right conditions, and knowing when the job has stopped being a cleaning question and become an access question.
Before you start
- Walk the job: which panes open inwards, which are reachable from the ground, which are neither?
- Identify the glass: plain, self-cleaning coating, or film — filmed glass has its own rules.
- Plan quantities and time with the area & solution calculator and the time planner.
- For anything above hand reach, run the access decision sheet before fetching any equipment.
Inside windows
Inside faces collect film — cooking residue, candle soot, aerosols — rather than grit, so they need less water and more polish. Lay a towel on the sill, wet the glass lightly with your solution (a sprayer or a wrung applicator both work), agitate, then either squeegee downwards in short strokes or polish dry with a flat-weave cloth. The order of work in a room: top panes before bottom, glass before frames, and finish each pane before moving on so drips never dry where you have already been. Kärcher’s guidance describes the same wet-then-remove sequence for interior glass.[K]
Tilt-and-turn and pivot windows are the quiet win for upstairs rooms: many are designed so both faces clean from inside the room. Check the handle positions and the manual before assuming — and before anyone suggests leaning out. HSE’s window-cleaning guidance treats cleaning from inside as one of the first ways to avoid work at height altogether.[HSE]
Outside windows from the ground
Outside faces carry grit, so the wetting stage matters more: dry-wiping a gritty pane is how scratches happen. Wash generously first — a bucket, an applicator sleeve and enough solution to float the soil — then squeegee. For panes above comfortable hand reach, a telescopic pole moves the same method up the wall while your feet stay on the ground; the pole reach planner checks whether an entered pole actually reaches your geometry, and its stop conditions (electrical, thunder, wind, visibility, control) outrank any geometry. Pole work has its own hazard list even at ground level — hoses, slips, handling — set out in the HSE/FWC best-practice guide.[HSE/FWC]
The squeegee stroke, properly
- Start each stroke on wet glass, blade angled slightly towards the direction of travel.
- Overlap the previous stroke by a few centimetres so no wet band survives between passes.
- Wipe the blade with a damp cloth between strokes — a wet, dirty blade redeposits soil as a streak.
- Finish with the edges: a dry detailing cloth run around the perimeter picks up the water line.
Fan-style (snaking) strokes come with practice; parallel strokes with good overlap produce the same result a little more slowly and are the better habit while learning.
Streak control
Streaks have exactly four common causes, and each has a different fix:
| Symptom | Likely cause | Fix |
|---|---|---|
| Regular lines in the direction of the stroke | Nicked or rounded blade rubber | Rotate or replace the rubber |
| General haze that returns in sunlight | Too much detergent | Dose from the label, not by eye — see the solution guide |
| Drying spots on an otherwise clean pane | Hard tap water drying on the glass | Dry the pane before it air-dries, or use purified water |
| Smears at edges and corners | Damp or dirty finishing cloth | Swap to a dry, clean detailing cloth |
Direct summer sun makes every one of these worse by flash-drying the solution; work the shaded elevations first and come back. Overcast, mild and still is ideal window weather.[K]
Common failure modes
- Cleaning the shadow, not the soil. Half of “streaky glass” is a dirty other face. Check which side the marks are on before re-doing a clean pane.
- Skipping the first wash on outside glass. Grit plus pressure equals scratches — always float soil off before anything rubs.
- Wrong cloth discipline. One cloth for everything means silicone, polish or fabric softener ends up on the glass. Glass cloths live and wash separately.
- Detergent creep. “A bit more” each time until the water sheets sticky. Measured dosing exists for a reason.
- Improvised access. A chair, a windowsill, a lean — the failure mode that matters. If it needs height, it needs the high-windows decision process, not balance.
Quantities and time
For more than a couple of windows, planning beats guessing: the area & solution calculator turns pane sizes into glass area and label-based solution quantities, and the time planner turns area and your own measured pace into a defensible time estimate. Both are transparent arithmetic over your entered values, with the formula printed on the sheet.
Sources used on this sheet
- Kärcher UK — Cleaning windows: tips for a streak-free view · Publication date not stated · Accessed 2026-08-20
- Health and Safety Executive — Working at height whilst window cleaning · Publication date not stated · Accessed 2026-08-20
- Health and Safety Executive / Federation of Window Cleaners — Safety in window cleaning using water-fed pole systems · Best-practice guide, amended 2026-03-31 · Accessed 2026-08-20
Correction and version note: written for content contract 2026-08-20.2; sources accessed 2026-08-20. Corrections are recorded on the methodology sheet.