Window Restoration Glossary

Apron

An apron is the horizontal timber board fixed directly beneath a window sill on the interior, often used to cover […]

Architrave

An architrave is the decorative moulding that frames a window or door opening, covering the joint between the frame and […]

Annealed glass

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

Beading

Beading (also called glazing bead) is the thin strip of timber or moulding used to secure glass panes within a […]

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 […]

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 […]

Grilles

Grilles (also known as glazing bars or muntins) are the horizontal and vertical dividers that separate a window into smaller […]

Glazing Rail

A glazing rail is the horizontal timber member within a sash window that holds the glass panes in place, forming […]

Gas filled unit

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

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 […]

Outside lining

An outside lining (also known as an external reveal liner or box frame extension) is a timber component fitted to […]

Parting Bead

A parting bead is a slender strip of timber fixed vertically inside a sash window frame to separate the upper […]

Putty glazing

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

Single-hung window

A single-hung window features one fixed upper sash and one operable lower sash that slides vertically-common in early 20th-century British […]

Scotia moulding

Scotia moulding is a concave, quarter-round decorative trim commonly used in period joinery to soften the transition between surfaces-such as […]

Sill

The sill is the horizontal timber component at the base of a window frame, angled outward to shed rainwater away […]

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 pocket

A weight pocket (also called a sash box or window box) is the enclosed cavity within a sash window frame […]

Window Catch

A window catch is a simple locking or holding device fitted to sash or casement windows to keep them securely […]

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 […]