Owners of period properties and older homes should be rightly proud of the beautiful original features that imbue their buildings with a sense of heritage. But homes with history also carry a sense of responsibility that requires these buildings to be looked after properly.
When it comes to original timber sash windows, this isn’t always as straightforward as it seems. Sash windows come in a wide array of styles and configurations, some with intricate features that demand expert architectural and historical knowledge. If yours need attention, now is a good time to find out as much as you can about the ‘eyes’ of your house and sort out any problems before the weather turns autumnal.
- What type of sash windows do you have?
There are many different sash window designs adorning period homes, depending on when and in what style your house was built. Which one have you got? The two main styles are Georgian (featuring glazing bars and multiple panes of glass) and Victorian (one or two big panes in each moving sash), as shown in the photos below. Edwardian sash window designs often feature a combination.

Source: Georgian sash windows

Source: Victorian sash windows
Compare your windows to others in the immediate neighbourhood to detect similarities and differences in sills, sash horns, moulding profiles or glazing. All the information will help you repair or refurbish your period windows authentically and in keeping with the original character of the area.
2. How do sash windows work?
A working knowledge of the basic functionality of your sash windows is essential to help you spot if there’s anything wrong. Sash windows are made up of an outer frame or box, typically with a pair of vertical sliders aka sashes. These can be adjusted so that both top and bottom sashes move, only one side moves, or both sides are fixed and don’t move at all.
The operating mechanism uses a pulley and counterweight system whereby cords are connected to weights that sit snugly inside the frame, counterbalancing the up/down movement of the sashes and holding them in the desired place.

Source: LeLay
3. What can go wrong?
Timber sash windows need regular maintenance to ensure they keep working properly and to stop problems from occurring. Check the timber and paintwork regularly and paint external sills annually to ensure they remain weather tight.
Since wood is a living material, poor maintenance and general neglect can cause rot and decay. If your windows don’t slide up and down easily and have become sticky, poor redecoration may be the cause.
Wear and tear means that sash cords can become worn and break over time, and the weights can get lost in the sash box. If you have rattly or draughty windows, or rain is finding its way in from outside, this is an indication that there are gaps around the sashes.
When it comes to repairing your period sash windows, some jobs are more straightforward than others. Replacing the cords and weights inside the box frame is probably one of the easier (and cheaper) repair jobs to carry out.
4. How do you fix problems?
However, when it comes to timber repairs, extensive sectional repairs are often needed. This can include renewing the lower sill, renovating the existing box frame or replacing sash frames. For this, the window must be expertly taken apart, rotten timbers removed and new pieces spliced in, before the window can be reassembled, rehung and rebalanced.
5. Do you need professional help?
Unfortunately, the knowledge and carpentry work involved in sash window repair is too complex for a most regular DIYers. Period windows were not made to standard specifications, and any repair work will require exceptional attention to detail.
Your best bet is to source a professional sash window company, whose team should comprise dedicated craftsmen with the right credentials and plenty of experience of working on similar properties. Visit their workshop and ask for written references too, for your own peace of mind.
6. Should you install draught proofing?
Whether it’s cold draughts, rain or dirt coming in from outside, you can fill the gaps around the sashes by installing draught proofing to make your home more energy efficient and much cosier to live in.
Secondary glazing – fitting an additional glass pane on the inside of the window – is another option to improve thermal efficiency and reduce noise. It’s also the preferred choice for listed buildings or some conservation areas where double glazing may not be approved.
Ask your sash window repairer for details.
7. Do you need double glazing?
Most sash window refurbishment companies will offer a replacement double glazing option to fit into existing box frames. Using slimline glazing panels matched to the profile of the existing sashes, you can choose glass with acoustic or thermal properties and a wide range of timber options.
While fitting double glazing is not the same as a full window replacement, please note that you may still need planning permission from your local planning authority, especially if your building is listed or you living in a conservation area.