What are sash windows?

BY SCHNAUBER · THE SCHNAUBER JOURNAL · OCTOBER 2026

Sash windows open by sliding a glazed frame, called a sash, within an outer frame. The familiar British type has two sashes that move vertically, supported by cords and weights or spring balances. Timber sash windows are common on period homes, with proportions and glazing patterns that vary between buildings.

What is the sash in a sash window?

The sash is the framed part that holds the glass. It is separate from the outer frame fixed into the wall. In a sliding sash window it travels along a channel, rather than swinging on hinges. The word describes that opening arrangement; it does not tell you whether the frame is timber or another material, or whether the glass is single or double glazed.

On a typical vertical sash window, the lower sash sits towards the room and slides upwards. The upper sash sits behind it and can slide downwards if it is designed to open. When both move, it is often called a double-hung window. Some windows have only one opening sash. Horizontal sliding sashes also exist, so check the actual movement rather than relying on the name alone.

How do box sash and spiral balance windows work?

A traditional box sash uses cords running over pulleys to connect the moving sashes to counterweights. The weights travel inside hollow boxes at the sides of the outer frame. Their job is to balance the sash so that it can be moved and held at an open position. A box frame therefore has to accommodate more than the glass and the visible timber.

A spiral balance uses a spring mechanism at the side of the sash instead of a hanging counterweight in a box. This changes how the weight is supported, while keeping the sliding action. It does not by itself determine the glazing-bar pattern, timber finish or appearance of the whole window. Ask which mechanism is specified, where it sits and how it can be accessed for maintenance.

Schnauber’s timber sash windows include cords-and-weights and spring sash options. For any particular opening, have the mechanism and frame depth confirmed in the survey and written specification. A photograph of the front elevation cannot establish which balance system is hidden inside.

What are the main parts called?

Knowing a few names makes it easier to describe an existing window or read a proposal. Start with the two moving rectangles, then look at the frame, joints and strips around them. Do not force a painted-shut or damaged sash to identify its parts; ask someone competent to inspect it safely.

• Stiles: the vertical sides of each sash, holding the glass alongside its horizontal rails.
• Rails: the horizontal members of the sash. The meeting rails come together around the middle when the window is closed.
• Glazing bars: the narrow divisions forming a pane pattern. Confirm whether a proposed window uses separate panes or applied bars with a glazing unit.
• Staff bead and parting bead: strips associated with the sash channels. The parting bead separates the paths of the two sashes.
• Cill: the sloping lower part of the frame on the outside, which helps shed water away from the opening.
• Horns: short extensions of the sash stiles at a rail joint, seen on many later traditional designs.
• Fastener and lifts: the catch at the meeting rails and fittings used to move a sash. These are separate from the balancing mechanism.

Which sash styles belong to Georgian, Victorian and Edwardian homes?

Georgian windows are often associated with regular grids of smaller panes, such as six over six. Victorian examples often have fewer, larger panes, including two over two or one over one. Edwardian designs can combine smaller panes in an upper sash with a clearer lower sash. These are useful visual descriptions, not a reliable way to date every window.

House styles overlap, regional details vary and later replacements can disguise the original layout. Look at early photographs, surviving windows and the proportions of the opening before selecting a pattern from a catalogue. A tall narrow opening with fine bars can look very different if the meeting rail is moved or the frame becomes much wider, even when the overall pane count stays the same.

The Society for the Protection of Ancient Buildings explains sash operation and care, including why historic examples deserve to be retained. For a period house, matching the thickness and mouldings can matter as much as choosing a familiar period label. Avoid adding horns or bars solely because they are described as “heritage”.

When does a timber sash window fit a home?

A timber sash makes sense where the sliding layout and frame details belong to the building, or where a new design deliberately uses those proportions. A sash can open without a hinged leaf swinging outwards. Check how far each sash will move, how you will reach the catches and what safe cleaning arrangements are available for that floor.

Timber also needs an agreed care routine. Inspect coatings and drainage paths, keep moving parts in working order and follow the supplied maintenance instructions. Do not assume every modern sash tilts in for cleaning, or that a spring balance makes the complete window maintenance-free. Those are features to confirm for the specific product.

If you are still comparing opening styles, our sash or casement guide covers that decision. The timber casement windows page shows the hinged alternative. For the wider range, see our made-to-measure timber windows. This article explains what a sash is; it does not assume it is the right answer for every room.

Can a period sash have modern glazing?

A sliding sash can be made with modern glazing, but the glass, frame and balance system need to be specified together. Heavier glass affects the support required. Frame depth, glazing-bar details and the appearance of the panes also matter, especially where existing windows are unusually slender. Ask what the complete proposed window will look like inside and outside.

For a listed building or a home with planning restrictions, do not treat a product description as permission to change the windows. The Planning Portal’s doors and windows guidance sets out planning considerations. Check the particular proposal with the local planning authority before ordering where restrictions may apply. A conservation area and a listed building are different situations; the advice must relate to your property.

Existing historic joinery may be worth retaining. If your question is whether the current window can be kept, our sash window replacement guide addresses repair versus replacement. Start with its condition and significance rather than assuming that age alone means the whole frame must go.

What should you bring to a sash window survey?

1. Photograph the whole elevation and one window from inside and outside. Include the glazing bars, cill and any surviving fittings.
2. Note which sashes move, which rooms they serve and where opening or cleaning is awkward. Report sticking or damaged parts without forcing them.
3. Bring any old photographs or drawings that show the original pane pattern, plus information about listing or planning restrictions.
4. Ask the surveyor to record opening sizes, sash proportions, mechanism, glass, finish and any details that must match.
5. Confirm installation scope and exclusions in writing. The survey sets the price; there is no single sash-window cost that covers every opening.

Schnauber’s head office is at 44 Mill Road, Cambridge. Our area pages cover Cambridge, Ely and Saffron Walden. Use the existing quote form to request a free home survey and explain which windows you want to discuss. Photographs start the conversation; final measurements and the agreed specification belong in the survey.

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