Sliding Box Sash Windows

Taking into account any listed building requirements these traditional timber windows 9 times out of 10 can be repaired and restored to their former glory for a fraction of the price of a new window.

Repair & restoration

Sliding Box Sash Windows


At J Baker Carpentry we have repaired box sash windows in all sorts of buildings from the earliest 18th Century houses to modern day replacements.  When maintained correctly they often outlast any uPVC product.

What causes the rot?

The deterioration of a box sash window tends to happen when the painted surface is broken and the elements are able to penetrate the wood, in more modern examples the quality of the timber that they are built can also be a key factor to its lifespan.

We have worked on windows more than 200 years old where just one of the windows needed attention and the rest were fine purely due to it not being maintained as well as the others. Water ingress can be very destructive and only take a number of years to wreak havoc on a timber frame.

The extent of the damage often hidden under a flaking paint surface can be described like an iceberg as it can be far bigger than what you can see from the surface, hence people tend to leave things until the damage is much worse.

I regularly come across windows that have been previously repaired without taking the travel of the water into account this then at best just compounds the inevitable deterioration of the window or at worst introduce more water into the building causing a bigger issue.

What can be repaired?

The good news is that due to the material being wood its possible to repair the majority of windows. In my experience i have been able to repair 9 out of 10 windows. Each window is made up of components these components can be repaired or replaced, the key is to know when the repair process becomes more expensive than a new window.

One of the things to bare in mind when considering new timber windows, the cost of the fitting and making good on the window reveal, plaster work, decorating etc can increase the final cost considerably. 


The Repair Process

The process for repairing a box sash window tends to be a little bit more complex than a standard timber repair, as there are other components that need to be taken into account including the Pulleys, cord and weights. 

These also tend to need some form of attention whether just cleaning the surface and lubricating or replacement.


The process as a whole tends to be a methodical approach which if followed should result in a nice smooth sliding window.

Site Visit

Inspection of the window, advise on the next steps, repair or replace and an idea of time and cost.

Remove rot

The site will be protected with dust sheets then the job of removing the sashes and cutting out perished timbers.

Repair in situ

Where possible all repairs are done in situ this reduces the time on the jo.

Repair in workshop

Any more complex repairs that cannot be carried out on site will be taken back to the workshop.

Refit repaired window

After all repairs have been completed the window can be reconstucted including the correct weights to offset the sashes

Protect repaired surfaces

Any external repair work will be primed to protect until the final painted surface is applied.

Past Projects

Some examples of past projects to give you an idea what can be repaired.

Grade II Listed Georgian Home,

The project was to review and repair all of the windows in this 19th century home, due to its listed status it had to adhere to to the strict regulations set to ensure the historic fabric of the building was kept intact where possible.

Modern stables conversion,

19th century outbuilding converted in the 80s into houses, single window repair.

Grade II Listed Coach House, Monmouth

Old coach house with medieval beginnings, mid terrace needing window repairs throughout. Different aged examples showing the various styles of window as they were developed.