Planning Permission and Building Regulations

Planning permission

Internal works to a dwelling do not constitute development, so planning permission is not normally required for secondary glazing — including in a conservation area, where the controls bite on external appearance. Listed buildings are a separate regime and are covered in our dedicated consent guide.

• Not development: no planning application in normal cases
• Conservation area controls target the exterior
• Listed buildings follow a separate route

Building regulations that do apply

Part L (conservation of fuel and power) sets the thermal expectation, which a Low-E specification meets comfortably. Part F (ventilation) requires background ventilation provision to be maintained — the reason we assess trickle vents at survey. Part K (protection from falling, collision and impact) requires safety glazing in critical locations, broadly below 800 mm from floor level and beside doors.

FENSA, competent person schemes and why they do not apply

Self-certification schemes cover replacement windows in the external envelope. Secondary glazing is an additional internal layer, not a replacement, so a scheme notification is not the applicable mechanism. What you should hold instead is a written specification recording glass type, cavity, frame and U-value — which is what an EPC assessor or a purchaser's surveyor will actually ask for.

Means of escape

Where a window is a designated escape route, the secondary unit must be openable from inside without a key or tool. We identify these at survey and specify accordingly; you should not have to raise it.