Metal Window Restoration
Best Practice
Methods for Metal Window Restoration
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Trust specialists who’ve restored thousands of ferrous and non-ferrous metal casement windows. Our Metal Window Restoration services cover survey, repair, and conservation for heritage and commercial buildings—including recent projects at the Palace of Westminster, Kew Gardens, and leading department stores such as Liberty, John Lewis, and the Bakers Building. Where necessary, we manufacture like-for-like replacements, including non-ferrous components such as bronze stays and extruded copper lights, to preserve original character and performance.
Survey and Catalog
Prior to our work each window is visually and manually assessed, photographed and a report with location and designation details uploaded to a management software.
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Each frame is also catalogued, photographed and steel tagged by Arts Heritage and a continual itemised progress report updated for subcontractors and management team on site, enabling quick reporting and practical conservation. Our site team enter works data into tablets throughout the working day enabling real time co-ordination.
Removal
Casements are generally set into stone or timber rebates and fixed with steel or bronze screws into lead sleeves or directly into timber. Screws are often corroded; where we can withdraw the screw manually or using tapping and reverse-threading, those that cannot be used are either cut through the putty joint or drilled out. All retaining screws should be replaced with stainless steel to prevent future corrosion.
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Once fixings are cleared, the putty between surround and casement is carefully raked out by hand using hammer and chisel. Each frame is then released to the exterior and individually hoisted or carried to ground level.
Cleaning & Stabilisation
Each metal window is assessed before cleaning and after to mark damage and repair requirements. Where damaged elements do not require replacing a combination of methods can be used to consolidate the frames. Forging, welding, brazing etc)
In the image on the left the frames had been originally brazed and forged, where this had failed the elements were refinished and brazed once again in the traditional manner. Where elements had snapped or cracked, we employed modern welding techniques including electric welding and also bronze acetylene welding.
The surfaces were re finished using hand tools and light abrasives. Some parts were missing entirely. New components were manufactured to match and
incorporated. Some new windows needed to be
manufactured from scratch. To do this we disassembled the required window. Mapped the components and manufactured all the parts. The Windows were stamped internally with the new manufacture date visible only if removed.
Manufacture Replacement Parts
Where replication was required, we produced master copies to accommodate casting shrinkage. These masters are used to manufacture the full quantities in both ferrous and non-ferrous materials. We have our own foundry where we can cast in iron, bronze, silver and gold. In this example on the right each lever arm comprised three cast-iron components and four cast-brass components, with custom washers and pins made for final assembly. All components were produced using the original methods and traditional skills in our foundries and metalwork shops.
Repairs and Enabling Function
Once we have repaired or made the component parts the windows are assembled and tested for function.
Installation
Frames are bedded on new heritage putty in their original rebates. Even where the windows appear the same same size, they were often made by hand and therefore sizes varied significantly, so each frame is returned to its original opening.
Once positioned, and bedded on putty the frames are fixed stainless steel screws and a sealing putty applied an external bead to secure and weatherproof the joint. The surface was then lightly abraded by hand and finished with a brush-applied topcoat.
