Hong Kong flats are notorious for their small sizes and weird designs - window sills as big as a bed; balconies too narrow to be used; bathrooms barely big enough for a sink. The latest oddity that has come to public attention is removable "fixed windows" - an increasingly common feature used by property developers to get around environmental and planning rules. Most buyers are not even aware of it until the flat is handed over.

Tight building rules and limited living space mean residential projects are often approved with noise-mitigation requirements. This has prompted developers to turn normal windows into ones that do not open. They are supposed to be opened for maintenance purposes only. Some come with removable handles, which enables them to function like normal windows if needed. To the government, they are closed windows and therefore fulfil noise-control rules. But to residents, they can be opened, but doing so may expose them to noise that exceeds environmental standards. At least four housing projects put on sale over the past year observe the environmental rule by using such windows.

Some buyers probably do not mind the inconvenience caused as long as they have been alerted in advance. Unfortunately, some only find out after they get the flat, as the current rules only oblige developers to display fixed windows in show flats but not in illustrations. The information is often not clearly marked in the floor plan, or is buried in the fine print of sales brochures that can run to hundreds of pages. Such sales tactics go against the spirit of the new law mandating developers to provide clear and accurate details to buyers.