Low risk
The glass looked clean while wet, then dried covered in streaks, smears or cloudy patches.
Chalky white rings, spots or a milky haze that stay on the glass however hard you scrub.
Caution
Black speckling in the rubber gasket, along the sealant line or in the corners of the frame.
White uPVC that has gone yellow, grey or chalky, and will not come back with ordinary cleaner.
High risk
The conservatory roof panels have gone green, the glazing bars are streaked, and the room is noticeably darker.
The bedroom and landing windows have not been cleaned in years because there is no safe way to get at them.
Baked-on bird mess, sticky sap or honeydew that smears into a film instead of wiping off.
New or renovated windows covered in plaster dust, paint spots, silicone smears and cement splashes.
Loft and bathroom roof windows have gone grey and green outside, and the room has lost its daylight.
Water pooling in the bottom of the frame, a sliding door that grinds, and vents choked with dust.
Describe the job and get a fixed price from a local window cleaner.
