Windows, doors and glazing
A Crittall window is rusting at the cill and the opening light still shuts. What metal is failing, and what of the frame still closes?
The metal failing is the Crittall steel at the cill, where it is rusting, and the opening light still closes. Rust at the cill is corrosion of that steel, which is what the survey has recorded. The light still shutting means this note has not said the casement is jammed or that the whole frame has seized. The survey saw rust at the cill and a light that still shuts. It has not treated the steel, and it has not dismissed the rust as decoration.
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?
Crittall frames are steel, and they rust where water lingers. The cill is where water lingers. Rust can lift the putty and swell the section well before the opening light stops closing, so a casement that still shuts is not a clearance of the cill. The survey did not cut the rust back to sound metal, and it has not measured how deep the corrosion goes. This note is rust in the cill, with the light still operating.
Ask a metal-window specialist to look at the rust at the cill and to say whether that section can be repaired. Tell the solicitor the Crittall is rusting at the cill and the opening light still shuts. Do not replace the whole window on this note alone, and do not ignore the cill because the light closes. The survey has not specified the repair and it has not cleared the rest of the frame.
What should you ask your surveyor?
- Is the rust at the Crittall cill the metal that is failing?
- Does the opening light still shut?
- Has the survey left the depth of that rust unmeasured?
What are the typical next steps?
- Treat the cill rust as the failed metal, not a seized light.
- Ask a metal-window specialist to inspect the cill section.
- Do not replace the whole window on this note alone.
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
If condensation sits on the glass, is that the same as cill rust?
No. Condensation is moisture from room air on a cold surface. Rust at the cill is corrosion of the steel itself. The opening light still shuts, which is about the casement, not about the rust. The survey has not folded the two into one defect. Deal with the corroded cill as metal, not as mist on the pane.
Does a light that shuts mean the frame needs no work?
No. Shutting shows the opening part still closes. It does not restore steel that is rusting at the cill. The survey has not cleared the frame, and it has not said the whole window must be scrapped. The metal that is failing is the cill. A specialist should say what that section needs.