Windows, doors and glazing
What is secondary glazing, and why is it not a replacement window?
Secondary glazing is an extra pane or panel on the room side of the existing window. The original frame is still the window in the wall. A home survey should say if that extra pane hid the outer frame. It does not turn secondary glazing into a competent-person certificate, and it does not mean the outer sash is sound.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
People fit secondary glazing to cut draughts and noise, often on a sash they are not allowed to, or do not want to, remove. The surveyor may not be able to see the outer putty or the bottom rail without opening the inner panel. If it was screwed shut, say so in your questions: the outer window may be NI in all but name.
Removing it later is joinery, not a building-regulations application by itself, but altering the outer window may be. Listed-building consent is a further question where it applies. The survey grants none of that. There is no national price for taking secondary glazing out. Ask the firm that made it, or a joiner who can see the fixings.
What should you ask your surveyor?
- Could you open the secondary panel and see the outer frame?
- Is the outer window timber, and was any of it soft?
- Did the secondary glazing itself trap condensation?
What are the typical next steps?
- Ask for the outer frames to be described separately from the inner panels.
- Do not assume the house has new double glazing because the glass looks doubled.
- If the house is listed, ask the solicitor before you specify removing either layer.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Does secondary glazing stop rain?
No. Rain is stopped by the outer window and its junction with the wall. The inner pane can hide the stain until it is severe.
Is it the same as a sealed double-glazed unit?
No. A sealed unit is one manufactured panel. Secondary glazing is a second window on the inside.