- 8 September 2026|
- News|
- Daniel Anderson
If you own a period property with steel windows, you will know they can be one of the most distinctive features of a building’s history. Slim glazing bars, small panes and finely detailed steel frames can contribute significantly to the character of an older property. When those windows begin sticking, rusting or letting in draughts, it can be tempting to assume that replacement is the only option.
At Metwin, we specialise in the restoration, repair and replacement of steel windows, including Crittall Standard Metal Windows. Our approach is to assess the condition of the existing windows first and determine whether restoration can preserve the original frames while improving their performance and service life. Our restoration service is particularly suited to projects where retaining the character of a historic building is important.
In this guide, we explain our Crittall window restoration process step by step, from the initial assessment through to repair, finishing, reglazing and reinstallation.
Why restoration can be the best way forward
Steel windows are built differently from timber or uPVC windows, and the way they deteriorate is different too. Corrosion affecting the fabric of the window does not necessarily mean that the entire frame needs to be replaced.
Older windows can accumulate layers of old paint, surface corrosion and dirt over many years. Once these are removed, it is possible to assess the actual condition of the steel and identify whether individual sections require remedial work.
For properties where the original windows contribute to the architectural character of the building, restoration can also have an important conservation benefit. Keeping the original frames means retaining their proportions, glazing bar arrangement and overall appearance rather than replacing them with a modern interpretation.
That can be particularly important for historic buildings, listed properties and buildings in conservation areas, where retaining original features may form part of the project requirements.
There are circumstances where replacement will be the more appropriate option. Severely distorted frames, extensive corrosion or windows that have deteriorated beyond practical repair may need to be replaced. A detailed assessment is the best way to establish which approach is appropriate.
What are the signs that steel windows need restoration?
There are several signs that your windows may need attention, including:
- Difficulty opening and closing casements or a need to force them shut
- Rust appearing through the paintwork
- Flaking paint and deteriorating protective coatings
- Corrosion around glazing bars, joints or lower sections of the frame
- Draughts around opening casements
- Hardware, stays or hinges becoming difficult to operate
These problems do not automatically mean the window needs to be replaced. In many cases, they indicate that proper maintenance or repair is overdue.
A survey allows us to establish the extent of the problem before deciding whether repairs, refurbishment or complete restoration is the most suitable approach.
The Metwin Crittall window restoration process
Our restoration work is carried out through a detailed step-by-step process designed to give existing steelwork the best opportunity for a new lease of life.
Initial assessment and careful removal
The process begins with an assessment of the existing windows. We consider the condition of the steel, glazing, opening casements and associated components before deciding what work is required.
For off-site restoration, the windows are carefully removed and transported to our factory. Removing the units allows us to examine areas that may be difficult to access while they are installed and gives us the opportunity to carry out the restoration in a controlled environment.
Preparation and shot-blasting
Once the windows arrive at our works, the glazing rebates are cleaned and the ironmongery is removed. The frames are then prepared for in-house shot-blasting.
Shot-blasting removes old paint, surface corrosion and existing coatings, exposing the underlying steel. This is an important part of the process because it allows us to properly assess the condition of the original fabrication and identify areas that require repair.
Repair and restoration
Where corrosion or damage has affected the steel, individual sections can be repaired or replaced where appropriate. Frames can also be straightened, strengthened and fettled to restore their condition.
We pay close attention to the individual components of the window, including casements and joints, so that the restored sections work correctly with the original frame.
The aim is not simply to make the window look better. We want the restored work to integrate with the original steelwork while retaining the proportions, glazing bar arrangement and character of the existing window.
Hot-dip galvanising
Following repair, the frames are sent for galvanising. Hot-dip galvanising provides a protective zinc coating to the steel, helping to improve its resistance to corrosion.
This can be particularly valuable when restoring older steel windows, as some historic steel frames may not have originally benefited from galvanised protection.
The process is carried out as part of our wider restoration approach to improve the durability of the existing steelwork while retaining the appearance and character of the original windows.
Finishing
Once the frames return from galvanising, they are reassembled and prepared for their final finish.
We use polyester powder coating in the required RAL colour to provide a durable protective finish. The choice of colour can be considered as part of the wider project, whether the aim is to replicate an existing appearance or introduce a different finish that is appropriate for the property.
Reglazing and reinstallation
The final stage involves reglazing and preparing the restored windows for installation.
Original ironmongery can be retained, refurbished and refitted where suitable, or replacement components can be provided where required. We can also discuss energy-efficient glazing solutions where improving thermal performance is part of the project.
The restored windows are then returned to site and carefully reinstated. They are mastic glazed and the casements and associated hardware are checked to ensure everything is operating as it should.
How long does Crittall window restoration take?
Every restoration project is different, so there is no single timescale that applies to every property.
The overall duration depends on factors such as the number of windows involved, their condition and the extent of repair required. More complex restoration projects can naturally require more work than windows that need relatively straightforward refurbishment.
Because our restoration process takes place off-site, much of the detailed work can be completed at our factory rather than inside the property. The openings can be temporarily protected while the windows are being restored before the finished units are returned for reinstallation.
We discuss the expected timescale during the assessment and quotation process so that you have a clearer understanding of what your individual project will involve.
Preserving character while improving performance
One of the main benefits of restoring original steel windows is the opportunity to retain features that contribute to the character of a property.
Original glazing bar patterns, slim steel profiles and opening casements can all form an important part of a historic building’s appearance. Replacing these features with a completely different window design can change the proportions and character of the property.
At Metwin, we look at the existing windows and the requirements of the building before recommending the most suitable approach. Where appropriate, restoration and glazing upgrades can provide a way of addressing issues such as corrosion, draughts and thermal performance while retaining as much of the original character as possible.
For listed buildings and properties in conservation areas, the relevant requirements should also be considered as part of the project. The approach will depend on the individual building and its significance, so professional assessment and appropriate permissions should be considered where required.
When is replacement more appropriate?
Restoration is not always the right solution.
Severe corrosion, significant distortion or extensive damage can sometimes make restoration impractical. In these situations, replacement may provide a more suitable long-term solution.
At Metwin, we can manufacture bespoke steel window solutions and replacement windows designed around the requirements of the project. Our manufacturing service combines traditional design considerations with modern production techniques, with a range of profiles and finishes available.
This is why we believe an assessment is so important. An older steel window should not automatically be considered beyond repair, but equally, restoration should not be recommended where replacement is the more appropriate option.
Looking after your restored steel windows
Restoration is an important step, but ongoing maintenance will also help protect the investment.
We recommend keeping an eye on your restored windows and dealing with small issues before they develop into larger problems. This can include:
- Inspecting the finish regularly for chips, damage or signs of corrosion
- Keeping drainage channels and weep holes clear
- Checking that casements continue to open and close smoothly
- Lubricating appropriate hinges, stays and locking mechanisms
- Addressing small areas of damaged coating as soon as they are noticed
- Keeping the lower sections of the frames clear of moisture and debris
Older windows may also have historic paint coatings that contain lead. Where this may be a concern, appropriate professional precautions should be taken when carrying out maintenance or repair work.
Regular maintenance can help protective coatings continue to do their job and can make it easier to identify potential problems at an early stage.
Why choose Metwin for Crittall window restoration?
Restoring steel windows requires an understanding of both the material and the building in which they are installed.
At Metwin, we combine our experience in steel window restoration with our wider expertise in manufacturing, installation and maintenance. We work on residential and commercial projects and can provide solutions ranging from individual repairs through to complete off-site restoration.
We also offer Crittall parts and service and maintenance, alongside our restoration, installation and manufacturing services.
Our approach is straightforward: assess the existing window first, understand what it needs and then determine whether repair, restoration or replacement is the most appropriate solution.
Get in touch with Metwin
If your Crittall or original steel windows are showing signs of corrosion, sticking, deteriorating paintwork or draughts, restoration could be worth considering before replacement.
At Metwin, we can assess your existing windows and discuss the most suitable approach, whether that involves minor repairs, complete off-site restoration, glazing upgrades or replacement.
To discuss your project with our team, contact Metwin or find out more about our Crittall window restoration service.
You can also call us on 020 8523 2081 or email enquiries@metwin.co.uk.
