Glass gets dirty from what is in the air around it. A house on a quiet residential street and a shop unit on a main road accumulate soil at completely different rates, so any fixed answer to how often is wrong for one of them.
There is also a maintenance argument. Grit left on glass and in frame channels is abrasive, and blocked drainage holes let water sit against seals, which shortens the life of the unit.
The short version
- Every four to eight weeks suits most homes
- Coastal, roadside and rural locations soil far faster
- Commercial frontages usually need fortnightly or monthly attention
- Frames, sills and drainage channels matter as much as the glass
- Cleaning in direct sun is the most common cause of streaks
A sensible starting point for homes
For an average home away from a main road, cleaning the outside every four to eight weeks keeps glass looking right without becoming a chore. Interiors need far less, typically two to four times a year, unless there is cooking or wood burning nearby.
The test is simple: if you can see the state of the glass from inside on a bright day, it is overdue. Once soil has been on glass for months it bonds and takes considerably more work to remove.
What makes glass dirty faster
Location dominates. Salt-laden air on the coast, traffic film on a main road, and agricultural dust in rural areas will all shorten the interval significantly.
Building specifics matter too: north-facing elevations stay damp and grow more algae, overhanging trees drop sap and bird soiling, and any nearby construction produces dust that sticks to glass in a way ordinary dirt does not.
- Coastal locations: salt film builds within weeks
- Main roads: traffic film is greasy and needs detergent, not water alone
- Trees overhead: sap and bird soiling, both acidic
- Nearby building work: fine dust bonds quickly to glass
- North-facing walls: algae and green film in damp months
Commercial premises are different
For any customer-facing business, window glass is part of the shopfront. Fingerprints on entrance doors accumulate within a day, and a smeared frontage undermines everything else you spend money on presenting well.
Most retail and hospitality frontages suit fortnightly external cleaning, with entrance door glass wiped daily as part of the internal routine. Offices with less passing footfall commonly work on a monthly or six-weekly cycle.
Frames, sills and drainage
Cleaning glass and ignoring the frame is a false economy. Grit sitting in the channel gets dragged across the seal every time the window opens, and the drainage holes at the bottom of the frame block with debris.
When those holes block, water pools inside the frame instead of draining out. Over time that causes staining, encourages mould on the internal reveal, and puts constant moisture against the seals of the sealed unit.
- Clear the small drainage slots at the bottom of the outer frame
- Vacuum grit from the channel before wiping
- Wipe seals with a damp cloth only, no solvents
- Check for misting between panes, which means a failed unit
Getting a streak-free finish
Streaks are usually caused by cleaning in direct sunlight, using too much detergent, or using a cloth that has been washed with fabric conditioner. All three leave a film.
A small amount of detergent in water, a squeegee drawn in overlapping passes, and a dry microfibre for the edges will beat any spray-and-wipe method. Wipe the squeegee blade between passes.
Working safely and knowing the limit
Ground-floor windows are straightforward. Anything above that changes the risk profile entirely, and ladder falls at home are common enough that it is worth thinking about seriously.
Modern pole-fed systems reach upper floors from the ground, which is both safer and faster. Where access is genuinely difficult, or where the glass is above a conservatory or a sloped roof, it is a job for someone equipped for it.