Sash windows in a conservation area
In a conservation area you can normally replace like for like without consent, unless an Article 4 direction has removed that right on your elevation. Where Article 4 applies, the front elevation usually has to be timber, in the original section, with the original opening pattern and glazing bar layout. Check the designation before you price anything.
Which applies to you
- Conservation area, no Article 4
Like-for-like replacement is normally permitted development on a house. Timber sash at 48 mm sightlines with 14 mm slim units is the safe specification and keeps the option open if the designation changes.
- Article 4 direction on the front elevation
Timber, matched section, matched glazing bars, and normally a planning application with a section drawing. Rear and side elevations are often unrestricted, so the house can be done in two specifications.
- A listed building
Listed building consent, always, even for like-for-like. Expect single glazing or slim units with putty-line detailing, and expect the conservation officer to want a 1:1 section.
- You want modern performance
Slim 14 mm units give Ug 1.4 in a traditional section. Acoustic laminate reaches 39 dB in a sash, which is lower than a casement because a sash seals with brushes rather than compression.
The figures behind it
- Sash sightline
- 48 mm
- Maximum sash
- 1400 x 2400 mm
- Slim unit
- 14 mm, Ug 1.4, fits a 24 mm rebate
- Best acoustic figure
- 39 dB with laminate
- Repaint interval
- About 8 years; cords about 30
