If you live in a Victorian, Georgian or Edwardian home in London, your sash windows are part of the character of your property, but they can also be one of the main sources of cold, noise and ongoing maintenance.
One of the most common questions we’re asked is:
“Should we repair our sash windows, or is it time to replace them?”
This guide walks you through the pros and cons of each, typical costs, common mistakes, and how to know what’s right for your home.
No right or wrong answer applies to every window. The best choice depends on:
The goal of this guide is simple:
Help you make an informed decision without any sales pressure.
Repairs are appropriate when:
Many homeowners start with the assumption that repairing must be cheaper.
But this isn’t always the case.
If a sash window is very rotten, the total cost can include:
It is common for repair quotes in these situations to reach £1,200–£2000+.
That is not far off and sometimes more than the cost of a brand-new custom-made double-glazed sash window.
For homeowners wanting long-term warmth, quiet rooms, low maintenance and reliable operation, replacement often gives better value.
Replacement makes sense when:
A simple decision framework:
You don’t need to guess.
A quick assessment from an experienced sash window specialist can tell you instantly which option makes the most sense, repair or replace, and why.
At Novells Sash Windows, we’ve been helping homeowners across London make the right choice for over 20 years.
Sometimes repair is right.
Sometimes replacement is right.
Our job is simply to give you the truth.
If rot is surface level and localised, repairs can work well.
If rot is deep, structural, or spreading into the box frame or sill, repair costs rise quickly and often approach (or exceed) the cost of a full replacement. A professional assessment is usually needed because rot in old frames is often hidden beneath paint.
Sometimes, but not always.
Small repairs (£300–£700) are cheaper.
But when a window needs:
…it’s common for repair quotes to reach £1,200–£2,000+, which is not far off the cost of a brand new double glazed sash window (£2,650 + VAT).
Repairs may reduce minor problems but won’t significantly improve heat retention.
If warmth is a priority, new double-glazed sash windows will make a noticeable difference.
Repairs offer minimal noise improvement.
Replacement with sealed double glazing offers significant noise reduction — especially on busy London roads like Wandsworth Bridge Road, Upper Richmond Road, or Garratt Lane.
In most homes not in a conservation area, no.
In conservation areas, the requirement varies. Often you can replace your windows like-for-like without full planning permission, but rules differ by council.
Most original Victorian and Edwardian sashes don’t have the depth to take double glazing.
You can draught-proof them, but true energy performance improvements come with replacement double-glazed sashes or complete new box frames.
Modern Accoya, hardwood or engineered Redwood sash windows can last 50+ years with minimal maintenance.
Old pine windows often reach their limit after 100+ years, especially where water has penetrated the joints.
No, modern custom made wooden sash windows are built to match the original profiles.
The glazing bars, profiles, horns and proportions are made like-for-like, but with modern performance.
Remember: repairs often require a painter afterwards, whereas new windows arrive fully painted.
Not usually.
Condensation is caused by warm indoor air hitting cold glass.
Single-glazed originals stay cold, so condensation returns.
Replacement with quality double glazing is the only reliable long-term solution.
As Co-founder of Novells Sash Windows, Philip has spent over 20 years perfecting the craft of designing, supplying, and fitting luxury wooden double-glazed box sash windows.
A family-run business led by Philip and his wife Nicola, Novells has fitted thousands of wooden windows across London and Surrey, with clients including Vivienne Westwood and the Victoria & Albert Museum.
