Box sashes are a living testament to the durability of timber, proving that when built into a brickwork reveal, with a stone cill to shed water and selected softwood for each section, they will equal the performance of any other window system, and beat most. What’s more, timber box sashes use no internal or external space, provide secure ventilation and can be produced in a wide range of styles to suit their environment.

Peter Wall is proprietor of Windows In Wood, a perfect example of a small joinery company that takes pride in maintaining and replacing box sashes in London. His clients come to him through word of mouth and he’s never short of work, as London has seen a huge resurgence in replacing box sashes. “I used to see guys ripping them out out and fitting aluminium units,” Mr Wall explained, “then uPVC came along and really took over, but even during that time there was always a big demand for timber. Now it’s busier than ever before, as people want traditional products.”

This has come at the same time as strict enforcement of planning laws. In the past they were flouted, causing some horrific sights in inner city areas, where window designs that had no relevance to their surroundings were fitted, mainly on grounds of price.

Double- and sound-reduction glazing, draught proofing systems and the revival of hardwood cills have all contributed to this increased demand, creating a market for quality replacement box sash windows.

Mr Wall and his colleague, Jim, showed us a typical job from start to finish, with Damon Keating from T Brewer & Co, his timber supplier, to assist and document the whole process. Having measured the existing openings, Mr Wall always starts by buying the timber sections needed for the specific job. “I keep some stock,” said Mr Wall, “but it’s best to use bright, fresh timber to ensure a really good job, so I’m regularly at the timber yard, checking that each piece is up to standard.”

A box sash consists of many components. Broadly speaking, the top and bottom sashes require stiles, meeting rails and a heavy bottom rail, while the box itself requires pulley stiles and sections to create the box space, which the sash weights hang in. The sash weights, which are fixed by cords hung over axle pulleys, equal the weight of the glazed sash so they glide smoothly up and down.

&#8220It’s best to use bright, fresh timber to ensure a really good job so I’m regularly at the timber yard, checking that each piece is up to standard”

Wood In Windows proprietor Peter Wall

In the workshop the box units and sashes are made to the exact size of the relevant openings and primed ready for final painting on site. This is a time-consuming and skilled process, ensuring that each component fits together. Some pieces, such as the parting and staff beads, have to be fitted on site, after the sashes are placed in position. These beads ‘lock’ the sashes into place and create the tracks for them to run up and down in, on the pulley stiles of the box frame.

Having arrived on site, Mr Wall and Jim start by chopping out the old units. One of the points often missed by people is that old timber is biodegradable and this is a tremendous benefit over aluminium or uPVC. “These windows are often 60 years old, but I recently replaced a set in Wimbledon that were over 100 years old,” said Mr Wall. “They’re a superb product and will outlast anything else, providing they’re looked after.”

The next step is to protect the room with temporary screening while the new box frame is installed. Once this is set in place, the sashes are fitted and glazed. Glazing methods have changed enormously from the days of putty, with special compounds and beads ensuring longer life spans for glazing units. The final part is to connect the sashes to the sash cords and weights and then check that they all run smoothly.

Once the box frames are installed, internal architraves and sections are fitted to tidy the surrounding wall and ceiling, leaving the painters to finish all internal and external decoration. “I always try to work with the same team on decoration as they keep the same standards as me,” said Mr Wall.

It’s this team work and reliance on each other, as well as the sheer history of box sash windows, that creates an enthusiasm from every member of the team to give of their best. In turn customers pick up on this professionalism; no wonder timber box sash windows are seeing such a resurgence.