Ruthin has a good deal of housing stock that predates uPVC by a century or two, and it behaves differently. Timber sashes swell, drop and stick. The glass is often original, thin, and in places has that gentle waviness that catches the light. It is worth cleaning carefully because it cannot be replaced with anything that looks the same.
The first rule with old sashes is water discipline. Timber frames that have been painted a dozen times have gaps under the paint, and flooding the frame pushes water into the joinery where it sits and rots. Less flow, more control, and dry the sill rather than leaving standing water on it.
Leaded lights need a light hand
Leaded lights need even more care. The came is soft, the cement between glass and lead is often perished, and pressing on a panel with a squeegee will move it. Work the small quarries individually with a light hand, and if a panel is already bowed, photograph it and mention it before you touch it. That conversation is much easier before than after.
Secondary glazing is common in the older properties and is nearly always dirtier on the inside face than anything on the outside. It is an internal job, it needs the units unclipping, and it should be priced as its own visit rather than absorbed into a round.
These houses are also where the best work is. Owners of old buildings tend to understand that things take time, and once you are trusted on a listed frontage you tend to stay on it. ▪