Window Restoration Glossary

Annealed glass

Annealed glass is standard, untreated float glass that has been cooled slowly in a controlled process (annealing) to relieve internal […]

Accoya® wood

Accoya® wood stands as a top-quality timber product which comes from sustainable sources and undergoes acetylation to improve its natural […]

Awning windows

An outward swinging window unit opening from the bottom and hinged at the top. Benefits of this window style include […]

Bottom Rail

The bottom rail is the lowest horizontal member of a window sash, forming the base that supports the glass and […]

Bay window

A bay window is a building element which projects from exterior walls by extending outward into space. The typical design […]

Bow sash window

The bow sash (or bow-faced sash) is a unique and particularly attractive form of sash window. Existing in a few […]

Casement Window

A casement window functions as a window which has its hinge on one side to allow it to swing open […]

Conservation area

A Conservation Area represents a special designation which local planning authorities in the UK assign to areas that show exceptional […]

Conservation Glazing

Conservation Glazing refers to high-performance window upgrades-such as slimline double glazing or vacuum insulated glazing (VIG)-specifically designed for use in […]

Draught-Proofing

Draught-proofing (sash windows) involves sealing the moving sash gaps to stop cold air from entering while enhancing heat retention and […]

Double glazing

Double glazing is a window construction method which employs two glass panes that remain separated by a sealed air or […]

Dormer window

Dormer windows are instantly recognisable features of much historic European architecture and describe a window set into a sloping roof. […]

Edwardian Sash Windows

Edwardian sash windows (1901–1918) are known for their lighter, more airy appearance compared to Victorian predecessors-often featuring larger panes, simpler […]

Float glass

Float glass is the standard, high-clarity flat glass used in most modern windows. It’s made by floating molten glass on […]

Fixed window

A fixed window serves as a stationary glazed panel which allows maximum sunlight entry while providing expansive view access but […]

Fitch fastener

The Fitch fastener exists as a discreet window lock which applies directly to surfaces and serves heritage sash and casement […]

Gas filled unit

A gas-filled unit is a type of double or triple glazing where the space between panes is filled with an […]

Glazing bar

A glazing bar serves as a horizontal or vertical bar which functions structurally or decoratively to divide window sashes into […]

Georgian sash

Georgian sash windows are characterised by their elegant, symmetrical design and multi-pane glazing-most iconically in a six-over-six configuration (six panes […]

Half Georgian Sash

Half Georgian sash windows feature a traditional six-over-six (or similar) glazing bar pattern on the upper sash, while the lower […]

Hinged windows

Hinged windows are a category of operable windows that swing open on hinges-most commonly including casement (side-hung) and awning (top-hung) […]

Intumescent seal

An intumescent seal is a fire-resistant strip installed in window and door frames that expands dramatically when exposed to high […]

Lift

A lift (or sash lift) is a small, often brass or timber handle fitted to the bottom rail of a […]

Lead

Lead has been used for centuries in traditional windows-primarily as counterweights in sash window box frames and occasionally in leaded […]

Laminated glass

Laminated glass consists of two or more layers of glass bonded together with a tough, transparent interlayer-typically polyvinyl butyral (PVB) […]

Meeting Rail

The meeting rail is the horizontal edge where the upper and lower sashes of a double-hung window come together when […]

Microporous paint

Microporous paint functions as a high-performing breathable coating which developers designed to protect exterior timber surfaces including windows and doors […]

Putty glazing

Putty glazing is the traditional method of securing glass panes into timber window frames using linseed oil-based putty (often called […]

Sash Weights

Sash weights are heavy counterbalances-traditionally made of lead or cast iron-hidden inside the box frame of a sash window. Connected […]

Sash horns

Sash horns are the projecting extensions at the top corners of a sash window’s lower sash (and sometimes the upper […]

Sash cords

Sash cords are the braided cotton or synthetic ropes traditionally used in counterbalanced sash windows to connect the moving sash […]

Top Rail

The top rail is the uppermost horizontal member of a window sash, forming the head of the frame that holds […]

Timber Sash Windows

Timber sash windows are traditional vertically sliding windows made from wood, typically featuring two counterbalanced sashes that glide within a […]

U-value

U-value measures how effectively a window resists heat transfer-the lower the U-value, the better the insulation. Expressed in W/m²K (watts […]

Victorian Sash Windows

Victorian sash windows are characterised by their taller proportions, often featuring a two-over-two or six-over-six glazing bar pattern, ornate sash […]

Vacuum Insulated Glazing (VIG)

Vacuum Insulated Glazing (VIG) is an advanced, ultra-thin double-glazing solution ideal for historic and period properties. The VIG system employs […]

Weight-and-pulley system

A weight-and-pulley system serves as the basic counterbalance mechanism which operates box sash windows. The system contains cast-iron or lead […]

Xenon

Inert, nontoxic gas. Xenon occasionally appears in high-performance insulating glazing units (IGUs) as a substitute for argon or krypton but […]