Sash windows repair

No unsightly patches after restoration. Sash Windows Repair with Guarantee for 10/15/20 years.

Sash windows repair

Sash windows refurbishment

We, Britons, love our heritage and try to preserve it at all costs. Traditional wooden windows, be it Georgian or Victorian sash windows, intricate casement windows and sliding windows are true gems of British architecture.

Like all wooden items, they need special attention and good care. Because windows are exposed to elements, their life span can become short without proper attention and protection.

Let’s look at the sash window restoration routes first:

Decorating route: Quick repairs with epoxy fillers

For many decades homeowners have been using decorators to paint and restore sash windows. The expectations towards such work, like the standards themselves, have never been too high. It is already a common practice to have timber windows repainted every three years.

Windows assesment uk
Windows assesment

What price decorators charge to paint the window

The average cost of 1 wooden window repainting is £120-£200. This does not include any repairs. If a window needs minor repairs, the price for wooden windows repairing and painting its exterior side is around £250-£270. It is worth knowing that such patch timber sash window repairs will not last longer than 2 years at best.

Short maintenance cycle

A typical 3-bedroom house has 10 windows, and a house owner would have to pay circa £2.5k every three years just to maintain windows, not to mention the time-consuming exercise of finding decorators, collecting quotes, arranging the work, dealing with delays and inevitable disruptions to your life of having tradesmen working outside of your house but still walking in and out. This is still a reality which many households in the UK exist in.

Sash Windows Repair: Local joiners route

However, in the recent few years a new service emerged – When people are looking for “sash window repair near me” services, they usually find window renovators. Such companies usually originate as joiners or builders, people who know a thing or two about windows. They renovate wooden windows by cutting out damaged areas and replacing them with new pieces of wood screwed into frames or cills. Any gaps are then filled with DryFlex, a two-component wood filler. Such repairs look significantly better than simple patch repairs. However, they, too, have their flaws.

Screws will move with the timber movement (shrinking and expanding when the temperature changes), pushing the screws and fillers up, damaging paint and leading to further wood decay when moisture gets in.

Also, these repairs are always visible when you look at a freshly repaired window. Some people accept this as an inevitable evil, others seem to accept these flaws as the character of old windows. Such sash windows repair may cost anything between £400 and £700 per window. This work is certainly not cheap.

decayed cutting in restoration

Windows replacement route

There is another, more radical, an option of replacing the windows altogether. The best thing about this solution is that the windows will look great. However, we see more downsides here than benefits.

First, is a huge cost, accounting for removal and disposal of existing windows, cost of the new windows and glass, their installation, rental of scaffolding, painting the windows inside and outside, making good and painting damaged walls.

If a house is listed or is in a conservation area, a house owner would need to jump through numerous hoops of getting a permit to replace.

Are there any long-term solutions for badly damaged windows?

Absolutely! At Chameleon, we renovate all types of wooden windows and provide a 20-year guarantee on all repairs and a 10-year guarantee on paintwork.

We use a combination of traditional sash window renovation with a lamination technique. Together they allow us to refurbish wooden windows back to their former glory without changing their look, no patches and complete peace of mind for decades to come.

A window will look the way it was first installed – no messy and uneven old paint, no signs of repairs, just clean lines and smooth surfaces with a window that is protected for decades, not just 3 or 5 years!

Sash windows repair using lamination technology

What does thorough timber window restoration and lamination look like? We remove all decayed and damaged timber, sand most of the paintwork down to bare wood, protect affected areas with wood hardener. The repairs are done with flexible wood fillers and resilient timbers, like Accoya and Tricoya, without any screws.

The whole length of a damaged rail is then laminated with Tricoya timber.

Tricoya man-made timber is guaranteed to last up to 30 years in the ground and over 50 years above ground, unprotected. When properly protected, it will last for as long as the house stands. This is the type of protection that will withstand even the harshest rains and the most dramatic temperature changes.

Sash Windows Repair
grade 2 listed building lamination

Lamination is widely used in construction and other industries like flooring, furniture production, car manufacturing among others. Laminating with Tricoya allows us to achieve an excellent level of timber protection without a heavy price tag.

Our method of renovating utilises our engineering background, joinery, carpentry and decorating skills. Some of the tools we use in our work we made from drawings, others were customised for the processes involved. Each repair is individual, yet follows a strict guidelines to achieve the highest quality and protection for the windows.

4 Steps to repair and upgrade your old sash window
4 Steps to repair and upgrade your old sash window 

Alternative to traditional putty

We repair and replace the missing putty with epoxy sealants. They are flexible, yet thoroughly stick to glass and timber, protecting the wood from moisture. No putty or beading could ever hold the glass and protect woodwork better than epoxy sealants. Under a coat of paint, they look identical to putty, keeping the historic look of the windows intact.

Sash windows paint spraying

Once all surfaces are properly protected and prepared for painting we then use paint sprayers. Paint sprayers apply an equivalent of up to 8 coats of paint when applied by brush. Here is the detailed guide to our exterior windows painting.

The paint coat is thick and even. The paint we use is flexible and allows for timber movement. The paint itself and the thickness of the coat applied thoroughly protect the woodwork from any possible natural damage.

brush paint layers

Also, when applied by a paint sprayer, the paint dries fast and the windows can be shut the very same day, making the inconvenience of keeping all doors and windows open all day and night a thing of the past.

Listed sash windows repair

Our renovation methodology is suitable for grade 2 listed buildings and those in conservation areas

Our method of renovating historic sash and casement windows is approved by conservation officers who regularly oversee our projects. Sash window renovation does not require any permission as it preserves and protects original features of a historic building.

At Chameleon we do all of the above work – renovation of historic wooden windows, draught proofing, slim double glazing and spray painting. We are a full service company for preservation and thermal efficiency of historic wooden windows.

Retrofitting of Double Glazing for Sash Windows

Rebates and weak frames in heritage sash windows

Old wooden Sash or Casement windows are always a challenge when it comes to existing sash windows double glazing. Rebates (a gap where a glass pane fits into) in such windows are quite narrow. Standard double glazing would simply not fit into such rebates. Also, frames need to be strong enough to carry the extra weight of double glazing.

Retrofitting of Double Glazing

Originally they were meant to carry the weight of a single glass. Installing double glazing into such frames will make them dangerous to operate. To make things even trickier, sash windows with a system of weights and pulleys need a competent adjustment to make sure the extra weight of double glazing does not impact their smooth operation. We work with Fineo glass. It is only 6.7mm thick, yet excels the thermal performance of a standard size triple glazing unit. It is an excellent choice for period properties. For windows with very narrow rebates, we have a tailor-made solution.

Not only do we widen such rebates, but also strengthen frames with slim metal frames strong enough to keep roof joists together so the windows can carry the extra weight of glass units and never again produce cracks at the joints. All these alterations are inconspicuous and will not alter the look of historic windows.

For sash windows, we add weights, change ropes, replace locks where necessary to ensure the windows work in a safe and smooth manner.

Fineo vacuum sealed ultra thin double glazing

Fineo glass is a new product on the market. It is less than a year old but is gaining wide popularity for its slim profile and excellent thermal efficiency. Slim double glazing unit exceeds the thermal efficiency of a standard-sized triple glazing unit. It is manufactured by AGC in conjunction with Panasonic in Europe.

Fineo has a market-leading 15-year guarantee. Most slim double-glazing systems only have a 5-year guarantee due to their use of inert gases, which escape over time, leading to loss of thermal efficiency. The Fineo glass is vacuum-sealed, making it more thermally efficient and robust.

Because of Fineo’s depth of only 6.7mm, it can be used in historic wooden windows with very slim rebates.

However, it is important to make sure that the frames are strong enough to carry the extra weight of the new glass. If the frames need strengthening, this must be done by specialists. These are rare, even among slim double glazing companies. We have such sash window renovation specialists at Chameleon. They will be happy to assess your double glazing project and provide tailor-made solutions for your windows.

If you live in an area with a high rate of house break-ins, you may want to consider installing reinforced slim double glazing. Just like standard slim double glazing, it will keep the historic look of the house, will be equally thermally effective and will protect your house from burglars. The company announced the production of its reinforced glass will begin in 2022.

Listed windows double glazing retrofitting

Double glazing retrofitting for Grade 2 listed buildings

Historic wooden windows need minor but very important adjustments before slim double glazing can be installed. Widening rebates and reinforcing frames are the most important adjustments.

We do them inconspicuously to comply with current regulations. This makes it possible for historic buildings to have windows renovated, double glazed and protected for decades to come.


As part of our sash windows repair and double glazing projects, we do draught-proofing. Draught-proofing is one of the most effective ways to save energy and money in any type of building.

Controlled ventilation helps reduce condensation and damp, by letting fresh air in when needed. Comprehensive draught-proofing can save up to 10% on energy bills.

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Ideally, draught-proofing should be done together with double glazing to maximize the energy-saving and reduce heat loss in houses to bare minimum. When done together with window renovation and/ or double glazing, draught-proofing will be almost twice cheaper than if done alone.

These jobs have many processes in common and create a significant saving for a homeowner not just on the energy bills but also on the cost of the work. However, if double glazing is not an option or you already have it and want to improve energy efficiency further, draught-proofing is the best solution to keep your home warm.

draught proofing sash windows


What kind of wood do you use?

In our timber window restoration projects we use Accoya and Tricoya wood.

Do you repair windows on Grade 2 listed buildings?

Yes, we regularly work with Grade 2 listed buildings and conservation area properties. We do like-for-like timber frame repairs. They do not require planning permission as we do not change the look of the windows.

Can you unblock stuck or painted-shut windows?

If your sash windows are stuck or painted shut we can unblock them, either by removing the problem paint during the restoration process or by changing sash cords, pulleys and rebalancing weights if needed to return windows to full functionality. We do these core repairs as a part of larger window restoration projects.

Can you replace broken glass panes?

We can replace broken or cracked glass. We also ensure that the new glass thickness and texture match that of the original glass.


Our projects

    Sash Windows restoration in the beautiful house in the heart of Cambridge

    Sash Windows restoration in the beautiful house in the heart of Cambridge

    Renovation of 60+ windows in one of the most beautiful houses in Bluntisham, Cambridge

    Renovation of 60+ windows in one of the most beautiful houses in Bluntisham, Cambridge

    Sash window refurbishment in Shepreth

    Sash window refurbishment in Shepreth

    Sash windows repair Godmanchester

    Sash windows repair Godmanchester