Windows, doors and glazing
Should Crittall W20 frames, seen beside top-hung hoppers, be treated as a verdict on rust at the bottom rail?
No. Crittall W20 frames beside top-hung hoppers are not a verdict on rust at the bottom rail. W20 is a slim steel window section. Hoppers are the small lights hinged at the top. Seeing the suite and those hoppers describes the windows. Rust at the bottom rail, where water sits, can thin the steel out of sight of a glance. The survey has not measured section loss, has not opened a joint, and has not decided the frames must be replaced.
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?
These steel windows rely on a thin section, putty and paint. The bottom rail collects water, so rust can start there under the paint and swell the metal. A top-hung hopper is a different leaf and can look fair while the rail below is scabbed. The survey named the frames and the hoppers. It did not measure how much solid steel is left, and it did not take paint off to look.
Tell the solicitor the frames and hoppers were identified, and that rust at the bottom rail was not given a verdict. A metal-window specialist can report on section loss if you need that, including whether repair or replacement is realistic. The home survey has not chosen. The lender has no measurement of the steel. Do not scrap the hoppers or the frames because they were named together. Paint and rust stay untested beneath the surface.
What should you ask your surveyor?
- Did you identify W20 frames without measuring the bottom rail?
- Were the top-hung hoppers a separate leaf from that rail?
- Has rust at the bottom rail been left without a verdict?
What are the typical next steps?
- Do not treat the frames and hoppers as a rust verdict.
- Ask a metal-window specialist if section loss must be known.
- Tell the solicitor the steel thickness was not measured.
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 an opening hopper mean the bottom rail is sound?
No. The hopper is the small top-hung light. The bottom rail is the horizontal member that holds water. One can move freely while the other is rusting under the paint. The survey did not use the hopper as a test of the rail. Movement of the leaf is not a thickness check.
If the paint looks whole, is the steel intact?
Not on this visit. Whole paint can hide rust on a slim steel section, especially on the bottom rail. The survey did not remove paint and did not measure the metal. A fair coat on W20 frames is not a verdict. What is left of the section stays unknown.