Original glass can often be an important part of the character of a traditional sash window. Whether it can be retained depends on its condition, the proposed repair and any glazing upgrade. Record significant panes before work starts and make the treatment of existing glass explicit in the quotation.
Why might old glass be worth retaining?
Historic panes can have subtle variations in surface and reflection that contribute to the appearance of an older building. Retaining serviceable glass also avoids replacing material unnecessarily. On listed buildings and sensitive traditional properties, the significance of existing glazing should be considered alongside the timber joinery.
Can putty be repaired without replacing the glass?
Sometimes. Failed or missing putty does not automatically mean that a sound pane needs replacement. The condition of the glass, rebate and surrounding timber should be assessed together. Where glazing work is required, ask how existing panes will be protected and whether removal is actually necessary.
What if a pane is cracked?
A damaged pane may need replacement for safety or weather-tightness. Ask the contractor to identify which pane is affected and what replacement glass is proposed. For a traditional elevation, appearance, thickness, safety requirements and any planning constraints may all be relevant to the specification.
What happens if you want better thermal performance?
Do not assume that existing glass must automatically be discarded. Draught proofing and secondary glazing can improve comfort while leaving the original panes in place. Where slimline double glazing is proposed within existing or new sashes, the dimensions, condition, glazing bars, weight and balance of the window need to be considered. Compare the options before deciding which historic material would be altered.
What should the quotation say?
Ask for existing glass to be identified by window reference and for the quotation to state whether it will be retained, temporarily removed, reset or replaced. If particular panes are important to you, photograph them beforehand. The specification should also describe putty work, timber repairs and final decoration so responsibility at the glazing edges is clear.
Related advice and services
- Sash window glass and putty repairs
- Can existing sash windows be double glazed?
- Draught proofing, secondary glazing or double glazing?
- Listed building and conservation guidance
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Discuss your glazing
For a property in Stirling or Central Scotland, contact The Sash and Case Window Company with photographs of the windows and any glass you particularly want to retain. A survey can establish suitable repair and glazing options.