Do You Need Planning Permission for Secondary Glazing?

The general rule

Planning control is principally concerned with external appearance and use. Secondary glazing changes neither. It is installed on the room side of an existing window, nothing is removed, nothing outside changes, and the whole installation can be unscrewed later. On an ordinary unlisted house outside a conservation area, no permission is required and no notification is needed.

Situation one: listed buildings

Listing protects the interior as well as the exterior, which is what catches people out. Works affecting the character of a listed building can require listed building consent, and internal glazing is within scope. In practice conservation officers regularly support secondary glazing because it is reversible and it protects historic windows, but the process still has to be followed. Speak to the conservation officer early and describe the fixing method and frame position.

• Listing covers interiors, not just elevations
• Consent may be required, so ask first
• Reversibility and minimal fixing are the key arguments
• Officers frequently recommend it as best practice

Situation two: conservation areas

Conservation area status controls external appearance, so internal secondary glazing is normally outside its scope even where an Article 4 direction restricts window replacement. Officers occasionally comment on how a frame reads from outside at ground floor level, which a slim section and a sympathetic colour resolves. A quick email to the planning department gives you something for the file.

Situation three: flats and leasehold property

Planning may not apply, but your lease almost certainly does. Many leases require landlord consent for alterations, and some define the window as part of the demised premises while others treat it as landlord retained. Because secondary glazing is internal and reversible it is usually straightforward to obtain consent, but it should be obtained in writing. Managing agents deal with this request routinely.

Situation four: rented property

Tenants need the landlord's permission for anything screwed to the fabric. Landlords are often receptive, because secondary glazing reduces condensation complaints and improves the energy rating, both of which are the landlord's problem. If permission is refused, a magnetic or film kit is the non permanent alternative.

Building regulations, briefly

Replacement windows are notifiable under building regulations. Secondary glazing generally is not, because the original window remains. Two requirements still deserve attention. First, escape windows: if a room relies on its window for means of escape, the secondary unit must be openable and usable in an emergency. Second, ventilation: do not remove or block existing background ventilation without providing an alternative.

What to do before you order

Check whether the building is listed on the national list, check the local authority map for conservation area boundaries and Article 4 directions, read your lease if you own a flat, and speak to the conservation officer if anything is ambiguous. Fifteen minutes at this stage prevents a problem you cannot easily undo. We survey with all of this in mind and will flag anything we notice.