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Jargon Buster

  • Back Addition

    The narrower part of a building, or wing, which extends rearwards beyond the “main“ structure, being an original feature rather than a subsequent extension. This is sometimes called an “outrigger“ in different parts of the country.


    A post or vertical pillar supporting a handrail or parapet rail.


    A railing supported by balusters, especially one forming an ornamental parapet to a balcony, bridge, or terrace.


    Another name for a fascia, sometimes decorative, placed along the verge of a roof at a gable end.

    Bay Poles or Bay Posts

    These are specially designed couplers used on bay windows. They come in a variety of angles either fixed or variable and form part of the structure as in they are load bearing. PVC-U frames themselves are not load bearing.

    Bay Window

    Multiple frames adjoined that jut beyond the facade. Brickwork around the frames follow the shape. Bay poles/ posts used as couplers and load bearing devices. Not to be confused with bow windows.


    British Board of Agrément. UK based approval body for the construction industry. Certificates are recognised by specifiers that the product has been assessed and will comply with Building Regulations.


    The PVC-U  section which securely clips in around a window’s glass unit, holding the glass in place and providing weather tight seal.

    Bearing plate

    A metal component used typically at the head and base of a bay pole/post which acts as a method to spread the load applied to the pole/post.


    Thickening out of render, in a curved shape, to form a drip to deflect water. Usually found at the base of a wall, above the damp-proof course.


    Bevelled finish also known as Chamfered refers to the angled edge detail around the frames apertures offering cleaner more minimal lines.

    Bevelled glass

    In the PVC-U industry, the term is used to describe a glass unit which includes decorative features usually consisting of a combination of cut glass bevels and lead.


    BFRC is the premier UK authority for independently verified ratings of energy efficient windows and doors. BFRC rated energy products carry a 'rainbow' label similar to those found on fridges, freezers, washing machines.

    Bi-fold Door

    A door consisting of anywhere between 2 and 7 panes which slide and fold back on themselves – creating a full width opening.


    Black, sticky substance, similar to asphalt. Used in sealants, mineral felts and damp-proof courses.


    The regular arrangements of bricks, blocks or stones in a wall so that the units may be joined together. The principal types of bond used in domestic construction are English, Flemish, header, stretcher, rat-trap, diagonal or garden wall bond.

    Bottom hung

    Also known as a hopper window, it is a type of opener which is hinged at the bottom and open inwards.

    Bow Window

    A different type of bay window, usually carrying only light loads and does not form an extension to the floor area of the room.

    Box sash

    Also known as vertical sliding windows, it is a type of window frame containing two elements which can slide up or down and occasionally tilt inwards also.


    The British Plastics Federation (BPF) is the leading trade association for the UK Plastic Industry, with over 400 members and 1200 affiliated members.


    A lintel, often timber, over an opening such as a fireplace or bay.

    Brush pile

    Also known as brush seal or wool pile, it is a flexible strip of fibres used around apertures or gaps around PVC-U openers and acts as a secondary seal.

    Bubble gasket

    A cylindrical shaped rubber seal generally used around sashes which creates a cushion like seal, especially effective when the gap varies between the window or door sash being closed and being locked as the hooks or bolts are engaged.

    Building Regulations

    Building Regulations are Government codes which set out the criteria that new building projects and refurbishment work must conform to. They help to ensure that buildings are safe, secure and energy efficient.

    Bump stop

    A device fitted to sliding doors or windows which allows the maximum opening of the sash to be restricted and therefore preventing clashing issues.

    Butt hinge

    A more traditional method of hinging sashes. Butt hinges stand proud of the door or window surface much like those commonly used on internal timber doors.


    A brick or stone support to a wall designed to resist lateral movement.

  • Cam adjuster

    A tool used to adjust the cylindrical locking of points known as cams used on some types of window and door hardware allowing fine tuning of compression or clearance where available.


    The lead bars in leaded light windows.


    An outward opening sash within a frame. Casement windows are generally internally beaded and incorporate two main seals. The most common type of UK window.


    The hollow space or gap between the external and internal skin of a building acting as an insulator and reduces the chance of moisture being transferred from one side to another through absorption.

    Cavity Tray

    A barrier inserted above a window or door to deflect moisture to the outer face, preventing internal damp. In many cases, this can be the lintel, though this arrangement is not always appropriate.

    Cavity wall

    A wall comprising of two leafs of masonry, tied together with proprietary metal ties with a hollow space or gap between the two skins.

    Cavity Wedge

    A simple device fixed between a sash and frame to assist in the alignment of the sash when closed and also offers an aspect of security and weather performance by reducing any possible movement.

    CE marking

    Conformité Européenne (CE) marking is a certification mark that indicates conformity with health, safety, and environmental protection standards for products sold within the European Economic Area.


    Chamfered finish also known as bevelled refers to the angled edge detail around the frames apertures offering cleaner more minimal lines.


    Window cill. The protruding lip at the bottom of a window or door that directs water away from brickwork.


    An older type of window handle that does not operate any gearing or hardware and simply secures the sash by use of a simple latch arrangement.


    Co-extrusion is the process of forcing two or more materials through the same dye to produce a single piece. This process is used in extruding a PVC-U profile and is also used to describe the process used to apply gaskets at the point of extrusion.

    Composite door

    A robust, secure style of door that looks and feels like a traditional timber door. It’s commonly made from an outer skin of GRP (Glass Reinforced Plastic) over a wooden or PVC-U frame infilled with foam insulation or similar.


    A single storey, ground floor extension to a domestic building made using a minimum of 75% glazing and separated from the main building constructed using frames and a roofing systems.

    Conservatory base

    The term is an industry term used to define the foundations and sub structure of the conservatory.

    Coping Stone

    Usually stone or concrete laid on top of a wall as a decorative finish and designed to stop rainwater soaking into the wall.


    Projection of stone, brick, timber or metal jutting out from a wall to support a weight above.

    Corner cleaner

    A type of machinery found in PVC-U frame manufacturing plants which removes the excess sprue (weld spill over) created when joining PVC-U profiles by fusion welding.


    A moulding at the junction between a wall and ceiling. Can also include a moulding at the top of an outside wall designed to project and throw raindrops clear of the wall.


    A type of ancillary profile or component used to connect two or more frames together vertically or horizontally. Made from a variety of materials, PVC-U, steel, aluminium, etc.

    Coupling Nut

    An alternative method of joining two frames together using a hidden nut designed to fit into the back legs of outer frames.


    Curved junction between wall and ceiling i.e.. a type of cornice.


    Projecting course of tiles to a wall or chimney to prevent rain from running down the face of the brickwork.


    This is the cover piece for the location where the roof glazing bars, ridge and eaves beams meet.

    Cruck Beams

    Pairs of curved timbers in period buildings which run from ground level and meet at the ridge.


    A dome or lantern shaped feature built on top of a roof.

    Curtain walling

    Glazed walling used in large buildings, often several storeys high (shop fronts/office buildings).

    Cycle testing

    A process of durability testing where the product is subjected to repeated cycles of the same motion.


    A piece of hardware used on all types of doors which allows a key to be used to operate locking mechanisms.

  • D mould

    A trim mainly used at installation stage to mask gaps around or between frames.


    The bottom one metre or so of wall clad with timber, originally designed to provide protection to the wall, and also covering the area most likely to be affected by rising damp. The top edge is finished with a Dado Rail.

    Damp Proof Course

    Layer of impervious material i.e. bitumen felt, incorporated into a walls designed to prevent rising damp to walls and lateral damp ingress around windows and doors etc.

    Damp Proof Course (DPC)

    A propriety moisture resistant strip built within the wall to resist damp usually 150mm above ground level to prevent moisture from the ground rising in the wall by capillary attraction.

    Damp Proof Membrane

    Horizontal layer of impervious material (usually polythene or bitumen) incorporated into floors or slabs.

    Dead load (self-weight)

    The load due to the weight of all walls, permanent partitions, floors, roofs and finishes including services and all other permanent construction.


    A feature on locking mechanisms, usually door locks, which provides a method of restricting how a lock can be operated and usually incorporates a rectangular bolt which engages the keep around the centre of the locking mechanism.

    Dog bolt

    A piece of hardware comprising of a static spike attached to a sash located on the hinge jamb which incorporates a spike shaped piece of hardware which engages into a keep pocket or plate and provides an additional locking point to heighten security.

    Door restrictor

    A piece of hardware used on all types of doors which allows the opening angle to be controlled. Most commonly used on open out doors to prevent wind folding the door back.

    Door slab

    Composite doors are offered in different thicknesses, the most common are 40mm, 44mm or, 68mm. A door slab is the term used to describe the sash part of a composite door assembly in either its raw machined or finished form.


    A construction with a window that projects from a sloping roof.

    Double glazing

    Glazing made up of two layers of glass with a space between them to improve insulation and reduce noise. Double glazing comes in several widths, although 24mm and 28mm are the most common.

    Double rebate

    A type of profile which comprises of two weather seals.

    Double sided tape

    Generally used in PVC-U frame manufacture to adhere Georgian bars to glass but is also used to attach and seal trims at installation stage or to add security as a seal on externally beaded glazing units.

    Drip bar or drip rail

    Part of a residential or composite door, located on the face of a door at the bottom externally the drip bar helps to deflect rainwater away from the door and prevent water pooling.

    Drop nose Cill

    A type of profile that is designed to be used as a window or door cill which has an extended overhang at the front edge to aid in directing moisture away from the brick work.

    Dummy sash

    A sash that does not open, usually included to enhance the appearance or symmetry of a window, mechanically fixed into the frame usually at the point of fabrication.

  • Easy clean

    Hardware used on side opening casement windows that allows an open window to be slid across the frame aperture and therefore provide access from indoors to allow cleaning from the inside.

    Edge banding

    Profile fixed around the edge of composite doors to house hardware and cover internal construction. Also describes a method of clamping mechanically jointed frames/sashes together during manufacture.


    Powdery white salts crystallized on the surface of a wall as a result of moisture evaporation.

    Egress hinge

    A window hinge allowing the maximum opening achievable to meet building regulations in regards to egress (emergency escape).

    Energy efficiency

    “Using less energy to provide the same level of service” is a general definition. In our industry that would be using less energy to keep a home at the desired comfortable heating level.

    Engineering Brick

    Particularly strong and dense type of brick, often used as a damp proof course in older buildings.

    English Bond

    Brickwork with alternating courses of headers and stretchers.

    Euro cylinder

    (See Cylinder) a Euro cylinder has a distinctive key hole shape. Often referred to as the door barrel.

    Euro cylinder

    (See Cylinder) a Euro cylinder has a distinctive key hole shape. Often referred to as the door barrel.

    Euro cylinder

    (See Cylinder) a Euro cylinder has a distinctive key hole shape. Often referred to as the door barrel.

    Euro cylinder

    (See Cylinder) a Euro cylinder has a distinctive key hole shape. Often referred to as the door barrel.

    Euro groove

    An industry standard dimensionally profile detail mainly found on sash profiles which allows the use of any hardware produced to suit it.


    A component which acts as a seal, usually found at the bottom of doors or where large gaps are necessary around openers. Also used a type of security device fitted to windows.

    Expanding foam

    A type of product generally used at installation which is used to fill gaps around frames when fitted.


    A manufacturer of linear lengths of material formed by material being forced through a die.


    Most of the profiles used in PVC-U windows, doors, conservatories and roofline are extruded. Extrusion is the process of pushing PVC-U through a die to form a solid shape.

  • Face fixed

    A term used to describe the location of a component, face fixed products are more visible and generally require less preparation work than concealed components.

    False mullion

    A mechanically fixed profile or section which creates rebates for two adjacent opening sashes to seal against but moves with one of the sashes to create larger unobstructed opening.


    Part of the roofline system that seals a house from the elements, between the tiles and the brickwork. Fascia is the front vertical board on the complete roofline system. Fascia is also sometimes used as the collective word for roofline.


    A thin strip of plastic, wood, cement, slate etc. used to fill a narrow joint.


    Final covering and treatment to a surface such as plaster, render, cladding etc.

    Fischer fixing

    A component sometimes used in the installation of PVC-U frames which functions in a similar way to a rawlplug.


    Component that is used to secure separate parts of the window or door set to each other, to secure the completed window or door set into the structural opening.

    Fixing brackets

    An alternative method of attaching frames into a structural opening, instead of fixing through the frame the "bracket" is attached to the back legs of the frame and the fixings are located in the protruding section of the bracket.

    Fixing foam

    A type of expanding foam used as a packer around frames in structural openings.

    Flag hinge

    A type of hardware, flag hinges are mainly used on doors and provide a simple hinge solution for fabricators and generally of easily accessible control over adjustment.

    Flank Wall

    A side wall.


    Sheet cover formed over a joint for waterproofing. Normally formed in metal or cement, creates a weatherproof and durable construction detail between a roof structure and the existing house wall.

    Flemish Bond

    Brickwork with alternating headers and stretchers in each course.

    Floating mullion

    See False Mullion

    Flush sash

    A type of casement sash designed to give the illusion of a more traditional looking window by sitting "flush" externally.

    Foil (lamination)

    The process of mechanically covering the PVC-U profile with an attractive non-peel coloured wood grained finish, giving it a totally different appearance and colour.


    Older, usually shallow, form or foundation of brick or stone.


    Means of distributing the structural loadings from a structure safely onto the ground.


    Normally concrete, laid underground as a structural base to a wall. In older buildings these may be brick or stone.

    Frame depth

    The distance horizontally from the front to the back of a profile, most commonly PVC frames are manufactured from profiles with a 70mm frame depth.

    Frame extension

    An ancillary profile used to increase the size of an outer frame profile by connecting to the back legs of the frame.

    Frame packer

    A component used at installation to wedge between the frame and brick work to assist in ensuring the frame is fixed solid and securely.

    French doors

    Double outward-opening doors that meet in the middle without a mullion, giving a clear unobstructed opening. Also manufactured as inward opening French doors occasionally.

    French mullion

    See False Mullion

    French windows

    Double outward opening windows that meet in the middle without a mullion, giving a clear unobstructed opening.

    Friction Stay

    The hardware used to hinge casement type windows to allow them open and stay open.

    Fully reversible (aka Top Swing)

    A type of window using special hinge hardware which allows the opening sash to pivot around the centre 180°, generally found in high rise buildings due to the ease of cleaning and weather performance.


    An alternative name for handles, knobs, locks etc. fitted to doors and windows.

  • Gable

    Upper section of a wall, usually triangular in shape, at each end of a ridged roof.


    The black rubber strip that runs around the pane of glass in a window to create a weatherproof join.

    Georgian bar

    Offers the illusion of small, individual panes of glass within a larger pane. Usually fitted within the cavity of the glazing unit.


    The Glass and Glazing Federation is the main representative organisation for companies involved in the manufacture of products and services for all types of glazing.

    Glazing bars

    A member, by which infill glazing or opaque panels are supported in conservatories, retained and made weather tight and secure.

    Glazing cassette

    A mechanically fixed sub frame used to secure glazing into composite door slabs. A male and female frame is loaded from each side sandwiching the glass unit into an aperture on the door slab.

    Glazing flipper

    Used in conjunction with glazing platforms, glazing packers are used to wedge between glass units and frames to securely fix glass in place with the aperture.

    Glazing packer

    Used in conjunction with glazing platforms, glazing packers are used to wedge between glass units and frames to securely fix glass in place with the aperture.

    Glazing platform

    Small but important PVC-U mouldings that support the glazed units when installing them into a PVC frame.


    Used for filling the joints between wall and floor tiles.


    Glass Reinforced Plastic - fibreglass. A tough material made of plastic/fine glass fibres. Used by the marine industry for hard-wearing/weatherproof qualities and as outer skins on composite doors.

  • Hardware

    Usually refers to the handles, hinges and other non PVC-U elements used on PVC doors, windows and conservatories.

    Head drip

    Head drips appear at the top of a window or door and are a means of channelling water away from the front face of the window or door.

    Head ventilator

    A device which clips to the top of the frame and allows the circulation of air to a property in a controlled and secure manner.

    Header Brick

    A brick laid end on.


    A type of door lock that throws a hook or multiple hooks into a keep when the door is locked.

  • Injection moulding

    The manufacturing technique used to make parts from both thermoplastic and thermosetting plastic materials.

    Inline patio door

    A sliding patio door system where the moving door pane slides in front of the fixed pane.


    A material which swells when heated protecting the material underneath or sealing a gap in a gap in the event of a fire. Used in strip form on fire rated products (Fire doors).


    The International Organisation for Standardisation (ISO) is an international standard-setting body composed of representatives from various national standards organisations. ISO sets standards for manufacturing and environmental processes.

  • Jacks (bay pole jacks)

    See bearing plate.


    Vertical section of a window or door.


    The mortar bedding between bricks or stones.


    A timber or steel beam directly supporting a floor or ceiling.

    Juliet balcony

    Often found in town houses or where living rooms, dining rooms or, kitchens are on the first floor. They comprise of a single or double door which opens inwards to allow maximum ventilation. Protection from falling is achieved with a balustrade.

  • Keeps

    The metal locking points found on doors or windows that are designed to accept the products locking mechanism.


    A type of decorative hardware used on doors, traditionally used of a method of attracting the occupiers attention.

  • Lantern roof

    A daylighting architectural element. Architectural lanterns are installed on top of larger roof and provide natural light into the space or room below. In contemporary use it is an architectural skylight structure.

    LAPFAG approval

    Local Authority PVCu Frame Advisory Group (LAPFAG) is made up of Local Authorities/Housing Associations/bodies engaged in the production/specification of PVCu windows.

    Large frame

    Also referred to as the Outer Frame, this is the part of the window or door that adheres to the building, remains static and houses the opening sashes transoms and mullions.


    A structure, the sloping roof of which abuts a higher wall.

    Lift & slide

    A type of sliding patio door in which the hardware raises the opening sash to allow it to slide along a track in front of the fixed panes.


    A horizontal beam over a door or window opening usually carrying the load of the wall above. Often lintels can be partially or completely hidden from view.


    Slats laid at an angle incorporated into a door or window. Can be hinged to allow ventilation/light.

    Low ‘e’ glass

    Low ‘e’- low emissivity glass. Varies from normal clear glass, one side has a metal low emissivity coating, it is insular glass and lets in energy from the sun and blocks heat loss from the home.

    Low threshold

    A product specifically designed to be used at the bottom of a door frame and will be small in height to reduce the amount of "step over" required to enter through the door.

  • Main frame

    The section of profile used to construct the outer frame of a window or door.


    An alternative name for the silicone seal between the outer frame and the wall, also used to seal all elements exposed to damp or moisture such as screw holes.


    A type of joint between two sections, usually at 90° to each other.


    Mixture of sand, cement (or lime), and water used to join stones, blocks or bricks, and for pointing and general filling.


    A mullion is the vertical structural profile which divides adjacent window units or elements.

    Multi chambered

    Refers to the inside of PVC profiles or frames and helps to prevent the transfer of heat from the inside to the outside of the property or vice versa.

  • Night vent

    A method of creating ventilation in a frame without compromising security, usually achieved by use of a secondary position on the window sashes keep plate allowing the sash to be locked fractionally open.

  • Ogee

    A shape where a concave arc flows into a convex arc.


    A term adopted by the conservatory market, this type of conservatory is usually constructed using full height brick walls with windows in them instead of fully glazed walls and glass roofing systems.

    Oriel bay

    An alternative term used to describe a bow window.

    Outer frame

    An alternative term for the main frame of a window system.

    Over scribed

    A joining method sometimes used for glazing beads. The first bead is cut square to the aperture size while the overlapping bead is shaped at the end to meet the first bead.


    Also known as the Sculptured, a more decorative style of edge detail found around the frames apertures or beads.

  • Part F

    Ventilation – Building Regulations. Part F sets out how much ventilation a building must have. Its impact on windows is often the addition of trickle vents.

    Part L

    Conservation of Fuel and Power – Building Regulations. Part L sets the thermal efficiency standards that buildings must comply with. All windows must now meet the standards set out in Part L.

    Part M

    Access to and use of Buildings – Building Regulations. Part M stipulates parameters for the width of front doors and the height of door thresholds, ensuring that people with reduced mobility can easily access buildings.

    Party Wall

    The wall which separates, but is shared by, adjoining properties.

    PAS 24

    PAS 24 – Enhanced security. PAS 24 is an accreditations that test the performance and security of windows & doors.


    The unit used to measure pressure, equal to one Newton per square metre.


    The term passive house refers to standard for energy efficiency in a building, reducing its ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or cooling.


    A licence for the sole right to exclude others from making, using or selling an invention, to protect the inventor from imitations.

    Patio door

    A set of doors with one or more glazed full sliding panels, often used to offer access to a garden.

    PCE gasket

    Low level gasket, fast fabrication/installation. Heat bonded gasket, no shrinkage/risk of wrong gasket being used. Gives a consistent quality/finish, stops stretching problems/maximises compression.

    Penning in (Pen in)

    A method of concealing the joint on coloured welded frames by use of a special coloured paint pen.


    A vertical column of brickwork or other material, used to strengthen the wall or to support a weight.


    Outer edge of mortar joint between bricks, stones etc.


    Polyvinyl Chloride- Unplasticised. Rigid plastic used in windows/doors. Low maintenance/long life. Term PVCu can be mistaken, including PVC/UPVC/UPVC/uPVC. Also known as plastic, e.g. plastic windows.


    Polyvinyl Chloride – Unplasticised expanded. Often referred to as foam products. PVC-Ue has a hard external finish and a slightly less dense core than PVC-U.

  • Q.lon

    A brand name for a seal which is made using a neoprene outer which is foam filled.


    A type of trim or finishing used at installation to mask gaps or steps.

  • Racking

    The distortion, or tendency to distort, laterally as in changing a rectangle to a non-rectangular parallelogram.


    Pitched, sloping or generally angled shaped frames.


    RAL numbers are the colour references used for matching colours on different types of products and surfaces.


    An overlapping section of a profile.

    Registered design

    Similar to a patent, however not as strict, a Registered Design relates to the overall appearance of the product resulting from one or more visual features.


    Usually made from steel, it offers additional strength properties to PVC profiles.

    Relieving Arch

    An additional arch over a lintel.


    Smooth or rough cast cement or lime based covering to a wall, either internally or externally, sometimes with pebbledash or other textured finish.

    Residential door

    A term used to describe a single door where the sash and frame are both made using PVC-U profiles and is glazed.


    A piece of hardware designed to control how far a sash can open.


    The visible faces around the aperture of the opening or frame.

    Reverse butt weld

    A manufacturing technique to join two or more pieces of profile together to create different facing rebates along the same length.

    Rider block

    A wedge shaped moulding designed to guide the sash into the correct position when closed to aid equal coverage of seals all round and alignment for locking points.

    Ring beam

    Horizontal structural beam used in conservatories to spread roof load onto the poles/posts/brick work housing the frames of the walls. Frames aren't structural elements & can’t take horizontal loads.

    Riser block

    See rider block

    Roof light

    A window fitted into a roof to create more light.

    Rough Cast

    A rough render finish to external walls.


    Rolled Steel Joist.

  • Sash

    The opening portion or element of a window or door.

    Saw centre

    A type of machinery found in PVC-U frame manufacturing plants capable of performing numerous functions or stages in the production of PVC-U frames, these can include cutting (saw), weld preparation, drain slotting and, routing for locks etc.


    Final smooth finish of a solid floor; usually cement or concrete.

    Screw port

    A hole or location specifically designed to take a fixing providing improved retention.

    Secured by Design

    Secured by Design (SBD) is the UK Police flagship initiative supporting the principles of “designing out crime”. Windows and doors that carry SBD approval have been assessed to provide a high degree of resistance to break-ins.

    Self-cleaning glass

    Glass that uses a dual-action process in which organic dirt is broken down by daylight and is then washed away by rain, thus making it easier to keep clean. Pilkington Activ and St Gobain Bio-clean are brand names for this type of glass.


    Horizontal external fascia boarding, usually timber or PVC-U that links together using a tongue & groove.

    Shuffle bead

    A type of clip in function used on glazing beads. A flat section of the bead sits underneath the glazing unit.

    Sight line

    The point at which the profile finishes and the visible glass begins.


    An alternative spelling of cill.

    Single leg bead

    A common clip function which uses a hook shaped leg to clip in and relies on the compression between the glass and profile to hold the bead in place.

    Single rebate

    A term used to describe a product which only utilises one rebate, commonly found on flush products such as composite doors or reversible and flush sash windows.


    A device found on hardware to retain another component, for example hold a latch back on a door lock.


    Part of the roofline system on a house that seals the house from the elements, between the tiles and the brickwork. Soffit is the horizontal part that runs from the fascia back to the house wall.

    Soldier Course

    A course of bricks set on end over a window or door opening.

    Solid floor

    A concrete floor slab constructed and supported directly from the ground.


    A type of hardware sometimes fitted to solid doors to allow visibility of callers from the inside.


    Ability of structure to weather forces caused by load conditions without serious deflection/damage & ability to shift loadings to ground. Loads are structure self-weight/loads of wind/snow/access.

    Stack Height

    The dimension between the outer frame and eurogroove which houses the friction stay.

    Stained glass

    A technique using special coloured dyes to create the effect of traditional stained glass windows.


    A brick or block laid length-ways.


    An alternative name for keeps used with locks.

    String Course

    A course of brickwork that projects beyond the face of an external wall.

    Sub frame

    A term used to describe the structural frame work within a product, for example a composite door may have a sub frame.

    Suspended floor

    Floor construction raised and suspended above the internal ground level and generally supported by the perimeter cavity walls, with possibly load bearing internal masonry walls to reduce the span of the floor.

  • Thermal break

    A carefully chosen material which acts as a way of reducing or heat or cold transfer between two surfaces. In windows, thermal breaks are often used within the double glazed unit in the form of warm edge spacer.

    Thermal efficiency

    “Using less energy to provide the same level of service” is a general definition. In our industry that would be using less energy to keep a home at the desired comfortable heating level.

    Thermal insert

    A specially designed product which can be inserted into the chambers of other profiles to change the thermal properties by creating more chambers for example.

    Through frame vent

    An optional built in feature to allow ventilation, located at the top of the window frame which passes through the frame.

    Thumb turn

    A type of door cylinder which includes a knob internally meaning no key is required to lock or unlock the door from the inside.

    Tie bars

    A metal bar connecting two components together to resist mutually opposing forces pulling the components apart often used in conservatories.

    Tilt and turn

    A window system that opens inwardly in two ways. Tilt and turn windows swing completely inwards allowing for easy cleaning. They also tilt at the top to provide good ventilation without leaving the window fully open.

    Tilt first (Turn first)

    Using alternative hardware the order in which a tilt & turn window operates can be controlled depending on the specifications requirements.

    Top Hung

    An alternative name sometimes used to describe a casement sash which is hinged horizontally with the handle at the bottom.

    Top Swing (aka fully reversible)

    Using specially designed hinges the sash can be rotated 180° completely outside the building allowing access to the outer pane for cleaning purposes.


    The horizontal structural profile that divides adjacent elements of windows or doors.

    Trickle vent

    A ventilation system built into the top of the window frame.

    Triple glazing

    Glazing units constructed from three panes of glass which are considered more thermally efficient than double glazed units.

    TS007 (3* combination for door handle & cylinder security)

    BSI TS007:2012, revised British Kitemark on euro cylinders/security hardware. Using parts of past tests i.e. BS EN 1303:2005/BS 3621:2007/PAS24:2007* & has more tests including “lock snapping”

    TS007 (3* combination for door handle & cylinder security)

    BSI TS007:2012, revised British Kitemark on euro cylinders/security hardware. Using parts of past tests i.e. BS EN 1303:2005/BS 3621:2007/PAS24:2007* & has more tests including “lock snapping”

    TS007 (3* combination for door handle & cylinder security)

    BSI TS007:2012, revised British Kitemark on euro cylinders/security hardware. Using parts of past tests i.e. BS EN 1303:2005/BS 3621:2007/PAS24:2007* & has more tests including “lock snapping”

  • U-value

    A measure of heat loss. The lower the U value, the more energy efficient the window.

  • Verge

    The edge of the roof, especially over a gable, or around a dormer window or skylight.

    Vertical slider

    A window in the style of a traditional vertical-sliding sash window. Vertical sliding windows often allow both the top and bottom frames to slide freely. The frames also tilt inwards for ease of cleaning.

  • Warm edge spacer

    A recent innovation that replaces the aluminium spacer. Used to separate the two panes of glass in a double-glazed unit with a spacer made of a different material (often plastic) that transmits less heat. This makes the window more energy efficient.


    A term used for type of machinery used to manufacture PVC-U frames. The ends of the cut profile are melted using heater plates and once softened forced together until cool and fused known as fusion welding.


    Window Energy Ratings– offering a way to show energy ratings of specific products. The ‘rainbow’ label is similar to those you see on refrigerators and other appliances, A+++ is the most efficient.

    Wind load

    The force applied to a structure as a result of the impact of wind. A term used to describe the imposed load an element may undergo taking the expected wind loads for its location to calculate its suitability or expected performance.

    Window board

    Used to create the internal window cill commonly manufactured from PVC-U or cellular based products.

    Window/door system fabricator

    The organisation responsible for the fabrication of the window or door.

    Window/doors system supplier

    The organisation responsible for designing and supplying the components used to manufacture windows and doors.

    Wool pile

    See brush pile.

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