A Guide To Window Terminology

A non-opening window which has the glass fixed directly into the wooden frame and is used for larger areas, allowing for maximum natural light.

Windows with a surface flush with the external frame that have a hinged opening, using a handle. Casement windows provide quick and easy ventilation and suit period, historical, traditional, and modern homes.

Small windows sometimes placed above a larger window to increase light or ventilation and can feature decorative glazing or shaped designs.

A non-opening window designed to allow light into a space while maintaining insulation and security. Often used alongside opening windows for a balanced design.

The appearance of a traditional flush casement, but with modern elements such as multipoint locking, 90º easy-clean side-hung friction hinges, or top-hung options. These can often be locked in a vent position for night-time airflow, and certain configurations can also meet fire egress regulations wherever required.

A classic window style with one or more moving glazed sash panels that slide vertically and are hung on pulleys with cords and balanced with weights. Often found in period properties, offering a timeless, elegant look.

The same elements and finish of a Sash/Box Sash window, but using a spiral or spring balance mechanism, often pre-tensioned to balance the weight of the sash and replacing the traditional cords and weights.

A variation of casement windows that open outwards, featuring a casement section that sits proud of the frame for extra protection against harsh weather conditions.

Slim bars that sit inside and outside the glass to give the appearance of smaller individual panes similar to traditional period windows. Also referred to as surface-mounted glazing bars.

A small strip of wood that safely secures the glass in place and can be used with glazing tapes and glazing silicon/sealant. While functional, beading can be decorative or plain and is an essential part of traditional and modern windows, holding window glazing or glass types in place.

The vertical sides of any window frame that support the frame connecting to the head and sill.

A vertical (Mullion) or horizontal (Transom) timber frame element which gives the overall frame essential structural support, or divides the window up for aesthetics.

An angled projecting sill will extend beyond the bottom of the window frame, helping to divert water away from the building and prevent water damage or damp. Stub sills serve the same purpose but will have a much shorter overhang.

The inner and outer parts of the opening or recess in a wall where the window frame is attached.

The vertical part of timber that forms the sides of a window casement or sash and gives structural support while holding the glass panes in place with the top and bottom rails.

The top rail is the horizontal piece at the top of a window casement or sash, while the bottom rail is at the bottom. Both work together with the Stiles to provide structural support and secure the glass panes.

The thermally efficient perimeter bar that holds the two pieces of glass apart to form a double glazed unit, reducing heat loss, minimising condensation, and improving energy efficiency compared to traditional metal spacers.

The outer section of any window that holds casements or glass in place.

A bevelled edge detail where a 45-degree angled cut is made to part of a timber edge, stopping before the end for a decorative finish.

A specific measurement to give a slight downward slope on a window sill, which directs water runoff away from the building to prevent moisture damage.

A decorative 45º angled edge applied to timber to improve the visual appeal of traditional and bespoke window designs. Different angles improve window visuals, improve light distribution, and can help with water runoff.

A drip groove or capillary groove is a shallow groove or channel typically cut into the underside of a window sill or frame. A drip can be a ledge or trim that juts out from the top of the window frame. Both direct rainwater away from the wall and the frame to prevent water damage and damp spots.

A narrow channel machine profiled into the timber section, typically used to create joins in timber lengths, or as a capillary groove to allow water to drip away from the window frame. Other uses may be purely aesthetic, i.e. decorative shadow detail features in functional elements like beading.

Associated with traditional sliding box sash windows, horns are a decorative component on the sashes.

A classic, subtle curved profile with a tapered end that adds a decorative yet authentic period detail to sash windows.

A decorative and elegant detail used on a casement window frame that creates a soft, curved shape popular on period properties.

A smooth, rounded edge decorative finish. Usually used to take the sharpness off and soften any edges while helping to reduce dents and dings.

A recess or step cut into the window frame allows for a secure fit for glass or sashes, giving an airtight and smooth operation.

This term simply refers to a clean, right-angled window frame where all four corners are at perfect 90º angles (square), ensuring a tight and proper fit.

A traditional woodworking technique where one timber piece has a ‘tongue’ that fits into the ‘groove’ of another piece to give a tight and seamless joint. Tongue and groove can also be used with the term ‘V Groove’, which is a 45º angle on the shoulders of the tongue and groove edges.

A standard recessed hinge where two plates are connected by a fixed pin and barrel, allowing smooth opening and closing of a casement window.

A multi-point locking mechanism commonly used inside a modern casement window. Operated by a handle, it engages the locking points for extra security.

Discreet ventilation openings typically built into the window frame or head of the window unit, allowing a controlled fresh air flow into the room when the window is closed, helping to reduce condensation and improve indoor air quality.

A high-quality timber product which is made by bonding layers of wood together for enhanced strength, stability, and durability compared to a natural solid piece of wood planked/cut out from the tree. Usually, the best small bits are cut out of the tree before being bonded to make the engineered wood, reducing waste and increasing product sustainability.

The natural pattern of the wood fibres that can make a difference to your window’s finished look and the wood’s workability. Grain can vary from one piece of the same material to the next, giving timber/wood its natural look without always conforming to a uniform look. The end grain refers to the exposed cross-section of the timber, which, unless properly finished and sealed, is vulnerable to moisture absorption.

Timber window frames can be crafted from either durable hardwoods like European Oak or tropical hardwoods such as Sapele, Utile, Meranti (or others including Iroko or Idigbo), or sustainable modified solid timbers like Accoya, or varying quality softwoods like Pine (often referred to as Scandanavian redwood in the trade), Douglas Fir, and Western Red Cedar. Other timbers may also come from the Eucalyptus family, used as Red Grandis, a hybrid laminated timber.

A natural imperfection in the timber where a branch once grew, which is darker in appearance. Knots can add character but may need additional treatment.

A breathable and flexible paint used on timber to allow moisture to escape while protecting it from rainwater for added durability and reduced maintenance.

Detailed technical drawings (drawn on computer) showing the elevation, plan, or cross-section of window elements, including thickness, moulding styles, and other section details and design elements. These drawings are sometimes a requirement to gain consent and planning permission for any listed building, but may also be used to ensure you receive the end product as agreed, even if planning isn’t needed.

A standardised colour-matching system used for paint or coating finishes to ensure consistent and precise colour choices across different materials and product ranges.