Windows

The Georgian period of house construction is dominated by vertical sliding sashes. These are very effective mechanisms for ventilation and provide one of the main style characteristics of the iconic Georgian house. They are a very robust design, but are prone to decay through age or poor maintenance. They have often sadly been replaced with uncompromising UPVC or casement windows, in the belief that these require less maintenance. From experience, such windows, if damaged, can be more expensive to maintain over their lifespan than the easier to repair timber originals.

A conservation officer will quite rightly be concerned that any work to sash windows should not detract from the character and historical significance of the house. This section is not intended to be a conservation guide. Seek advice before undertaking any work to sash windows in listed buildings or properties in conservation areas. There are many ways in which buildings can be kept, maintained and preserved, and so the various options have to be debated. There is always a balance to be struck between economics, practicality and theoretical excellence of conservation.

Draughts

The most common complaint against sash windows is draughts. These are caused by loose-fitting sashes and by downdraughts of cold air, from large panels of single glazing. Various options exist to reduce draughts, but it is always important to understand what is meant when an occupant complains of draughts. Elderly people, for example, feel draughts much more than younger people, and someone sat at a window for long periods may also perceive a colder area compared to elsewhere in the house. People who move from modern houses to Georgian properties can be surprised how 'airy' they are, and seek to seal them up by whatever means it takes. Often these actions have unfortunate consequences.

Loose-fitting sash frames can be attended to by removing and refixing the parting beads that keep the frames apart, and the staff beads that hold them in the frame. Careful preparation of the paint finishes can also keep the sash frames free enough to move, but not so loose as to cause draughts. The meeting rails can be adapted to meet in a close-fitting rebate, but this requires them to be removed and dealt with on a joiner's bench.

The removal of a sash frame is a straightforward operation, well within the capacity of a carpenter. If beads break, they can easily be replaced (the beading components are generally available from DIY stores) and the detachment and retention (and replacement, if necessary) of the sash cord is easily achieved.

Specialist joinery companies provide sash frame refurbishment with modern brush seals, and can even fit double-glazed units. However, the detailing of double glazing refurbishments for Georgian windows needs to be carefully considered, as the typically slender glazing bars will not be capable of housing thicker double-glazed units, and frames will require significant reinforcement if they are not to be pulled out of square by the greater weight of glass.

Simple measures to reduce the perception of draughts may include the moving of radiators near to the window, to allow a mix of warmer air to reduce the feel of draughts, or the introduction of thick curtains into a window reveal to mask draughts at night. If the windows are fitted with shutters, it might be easier to refurbish these to working order to give the occupant the facility to close the window off at night.

Secondary glazing

The most problematic issue of secondary glazing is the alignment of the meeting rails of the secondary glazing with that of the original window. When viewed from outside it can be very distracting to see a misalignment of these components, and some thought should be given to reducing or preventing this effect. When specifying secondary glazing, note the positions of the original meeting rails and glazing beads, and obtain drawings from the installer showing how the rails will align. It is important that the slenderness of the glazing bars is not compromised by thicker components in the secondary glazing. Operating the timber sash also needs to be considered - a common mistake is to install secondary glazing in such a way that a person cannot get access to the sashes to lift or lower them. Enquiries for listed building consent should be made and complied with before any work commences.

Damaged sash windows

Two main types of repair can be considered on timber windows:

• splicing; and
• resin repair.

The type of repair most appropriate for Georgian sash windows is hotly debated. Concerns centre on the practicalities of the timing of repairs, authenticity, cost and the distinction between basic repairs and full restoration. Conservation principles are not discussed here, but note that consultation is required when considering repairs to Georgian properties.

Splicing in new pieces of timber is seen by some as the only honest repair, but it is complicated to achieve a good splice on site that will last. Some site carpenters are not comfortable in undertaking what is essentially a joiner's job, and while some may be competent enough to perform a splice, it is difficult to consider a detailed and delicate splice as a carpentry task. A good splice will require the whole frame to be removed and transported to a joiner's shop.

With a resin repair, only the rotten wood is removed, the affected area is treated and a filling is inserted. The work can be sanded and painted in a day. This work can be undertaken by a carpenter on site without the need to remove the glass. Resins can also be used to act as an intermediate fill to bed new cill sections. The use of some resin fillers on site can however be problematic. There is nearly always a requirement by the manufacturers for the surfaces to be clean and dry and grease-free. This is technically possible, but in practice not easily achieved on site. If the mixing of the hardener and filler has to be undertaken on site, it is best to use systems that either have twin tube dispensers that mix in the correct ratio, or a system that changes colour when the correct mix is achieved. Blind mixing can make the mix too brittle or set too quickly. Some resins are very flexible, capable of being planed, sanded and drilled.

The components of a sash windows

It is important to remember that the jambs of the frame in a sash window are hollow, making splicing more difficult to achieve as there is less material to work with and the carpenter has to make what is essentially a new weight box. A splice to a cill where it meets the jambs is particularly difficult. Cill splices are best achieved by removing the entire front section and fixing new timber to the face.

Painting

Over-painting causes windows to be held shut and can make them stiff to operate. When specifying painting works for sash windows it is important to be realistic as to how much preparation will be required. Often it is not possible to fully understand the level of decay beneath the surface, and contingency sums are inevitable. If it is the intention to burn/strip the paint off back to bare wood, consider the amount of time that will take, given the surface area of the main channels in the frame. Close analysis of the tender price is required to ensure the contractor has allowed enough time for preparation. Cost control will be lost if arguments arise on site as to the intended level of preparation required. Leaving the contractor to assess how much work is likely to be needed when they tender will not produce tenders capable of comparison. For tendering purposes it is better to establish a rate for the work and a value of expected work with a contingency.

Lead has been used in paints for centuries, and was certainly used in the Georgian period. It is highly hazardous when sanded or burnt off. Make allowance for this when considering the exposure of painters during redecoration.

Operating a sash window

Many surveyors wish they had not tried to open a sash window, not least because sash frames have a habit of falling out if they are in a bad condition. The sash cords often break, and the weight of an upper sash can take you by surprise. Always try to rattle a sash window before you open it, because this will give you an indication of how likely it is to open (or fall out). If a window is stiff, take care when opening it so as not to pull it out of square or strain the lower joints. A common causes of damage to sash windows is forced operation when they start to stick. Constant straining will eventually cause the sash to break, and slamming the sash can cause the glass to break or crack.