Bottom Rail

The horizontal bar across the bottom of the window frame, which sits above the cill.


The lowest horizontal ledge or bar that forms the bottom of the window frame.

Double Glazing

Designed to reduce heat loss, noise and UV rays, double glazing consists of two panes of glass with a gas-filled space in-between.

Head Jamb

The first horizontal bar that forms the top of the window frame.

Leaded Bars

Leaded glazing bars are the thin strips of wood or metal that were originally used to separate and hold panes of glass in place. Today they provide a heritage-inspired, decorative effect – the most popular designs being diamond and square bars.


Fitting inside the window frame, the sash is the section that moves and holds the glass panes safely in place.

Secondary glazing

A single pane of glass fitted over existing single glazed windows, ideal for windows that cannot be altered due to planning restrictions, e.g. listed buildings and conservation areas.


The vertical edges of the window.

Top Rail

The horizontal bar across the top of the window frame, which sits underneath the Head Jamb.

Trickle vents

A trickle vent is the small slot or opening on a window that allows a room to remain ventilated when the window is closed.

Triple glazing

Designed to reduce heat loss, noise and UV rays even further, triple glazing consists of 3 panes of glass with two gas-filled spaces in-between.


U-values measure how easily heat can pass through a material; the lower the U-value, the more efficient the material. By law, window manufacturers in England and Wales must demonstrate that their windows comply with the latest energy efficiency requirements, which is usually done by declaring the windows' U-value. U-values for windows and doors must meet a minimum criteria, as stated by the latest building regulations.

Vertical Jamb

The vertical bars that form the sides of the window.


Based on a scale of G to A+ (A+ being the most efficient), the Window Energy Rating (WER) indicates how energy efficient your windows are.

Window finishes & materials

Astragal bars

Traditionally, windows were constructed with smaller panes of glass to create larger windows in the most economical way. These smaller panes of glass were connected together with slimline bars. These days, these authentic bars are only used for decorative purposes. Astragal bars are fitted to the window pane internally and externally to give the effect of multiple panes of glass.

Bevelled/Chamfered frames

Bevelled or chamfered windows have a flat, sloped profile, ideal for both traditional and new buildings.

Georgian bars

Georgian bars are also used to create period style windows, however they are sealed in between the layers of glazing rather than internally and externally.

Low-e glass

Low-emissivity glass is a very thin coating applied to windows that allows heat from the sun to enter and then reflects it back into the room, which works to reduce heating demand and energy bills.


A mullion is the vertical load bearing section that separates individual windows. A traditional example of a mullion is in a typical church building, where individual windows are separated by stone mullions. They can be made of virtually any material, with modern mullions commonly made from timber, aluminium, steel and uPVC.

Multi-chambered profiles

Windows that feature multi-chambered profiles boast higher thermal efficient qualities, thanks to intricate symmetrical chambers within the window profile. These chambers break up currents of cold air and lock in pockets of warm air to keep homes at a pleasant temperature, for longer.


A muntin is another term for a glazing bar; the strip that divides and holds individual panes of glass securely in place.

Ovolo frames

Ovolo or sculptured windows have a curved, decorative profile that’s ideal for period properties.

Sash horn

Sash horns are an original feature of authentic sliding sash windows and are usually curved or constructed in an elegant 's' shape design. Sash horns prevent timber windows from opening too much or getting jammed, as well as supporting the intricate elements of the window. As manufacturing technology has evolved, uPVC sliding sash windows have retained the classic sash horn detailing for decorative purposes only.


A transom is the horizontal version of the mullion and acts as a strengthening crossbar.

Warm Edge Spacer Bar

Positioned around the inside edge of the glass, warm edge spacer bars keep double or triple glazed window panes apart. This proactively reduces heat transfer and external noise, as well as preventing condensation from forming on your windows. The term ‘warm edge’ is used because foam spacer bars are up to 950% less conductive than aluminium.



Based on a scale of E to A++ (A++ being the most efficient), the Door Set Energy Rating (DSER) indicates how energy efficient your doors are.

Slave door

A door that is fixed in place, usually with a shoot bolt, e.g. French doors.

Traffic door

A traffic door is a conventional door that is built into a bifold door system. Depending on the number of door leaves, a traffic door can be hinged to the door-frame and operate independently or attached to the bifold system. Traffic doors save time in areas where it isn't practical to continually open the whole bifold system, as well as retaining warmth and saving money on heating bills throughout the winter months.

Door Security

Dog bolts

Hinge bolts (AKA ‘dog bolts’) are steel pins fitted into the hinge side of timber door-leaves to reinforce exposed hinges, or to inward opening doors that could be vulnerable to kicking or barging.

Multi-point locking

Multi-point locking systems dramatically heighten door security, by bolting the door into the frame and locking at multiple points with the simple turn of a key.

Door finishes & materials

ABS skin

Acrylonitrile Butadiene Styrene (ABS) is the same material used to make Lego. It is a coating used on timber core composite doors to strengthen them, actively resisting fading, discoloration and scratches.

GRP skin

Glass reinforced plastic (GRP) is a coating used on high-density polyurethane foam filled composite doors to strengthen them. GRP actively resists issues such as warping, twisting, rusting, peeling and fading.

Polyamide break

Also known as a thermal break barrier, polyamide breaks are a plastic barrier placed between the inner and outer frame of an aluminium door to make it more energy efficient.

Tempered glass

Also known as toughened or safety glass, tempered glass is made with controlled chemical & cooling methods that increase its strength; safely crumbling into small pieces when its broken.



The purpose of a cornice is to protect the structure from rainwater and hide the conservatory guttering and rafter ends, for a clean and attractive finish. Cornices can be added to new or existing conservatories, orangeries or extensions.

Internal downlights

Spotlights that are integrated into an extensions’ ceiling.

Internal plastered soffit system

A way to create a modern look inside a conservatory, offering effective ventilation so that air can flow freely through the roof area to provide additional protection against condensation.

Lantern roofs

Lantern roofs are made up of angled glazed panels that allow the light to flow in, which creates a stunning architectural glazed focal point. Lantern roofs can be added to conservatories, orangeries, extensions and any flat roofed structure.


Orangeries were originally built by wealthy landowners to protect their valuable citrus trees from wintery, icy conditions. Now added to homes in need of more space, light and character, orangeries feature brick and solid sections; ideally bridging the gap between conservatories and extensions.

Conservatory finishes & materials

Clad over roof

A conservatory clad over is when insulation, timber, tiles and plasterboard are typically placed over and fitted to an existing polycarbonate or glass conservatory roof. Read our blog post to find out why they should be avoided at all costs.

Crestings & finials

Typically recognised as stylish spikes positioned on top of conservatory or orangery roof frames, other than a decorative finishing touch, the primary function of crestings and finials is to deter pigeons and other birds from perching on the roof and making a mess and/or causing damage.

Insulated columns

5 times more thermally efficient than brick columns, insulated columns improve an extensions' energy efficiency thanks to their carbon-enriched filling, whilst adding a stylish modern twist.

Self-cleaning glass

Glass covered with an ultra-thin coating that reacts with daylight to break down dirt.

Polycarbonate roofing

Polycarbonate is a robust thermoplastic material, mainly used as a cost-effective, lightweight and tough conservatory roofing option.


Anti-jemmy bars

Secure metal strips that are fitted to the lock edge of outward opening doors and windows that prevent them from being prised open.

Argon gas cavity infills

Argon gas is inserted between the panes of glass in a window or door to increase its energy efficiency, due to the fact that argon has 34% lower thermal conductivity than air.

Bevelled glass

Bevelled glass is thick glass that has been cut to create an angled surface. Cut into diamonds, squares, rectangles, tear drops and many more distinctive shapes, bevelled glass creates attractive natural lighting effects.

Dual colour

Dual colour refers to windows, doors and frames that are different colours internally and externally.

Etched glass

Etched glass is a type of obscure glass that's created with a sandblasting technique, primarily used to enhance privacy levels without obscuring natural light from entering the space. A collection of artistic designs, in a range of privacy levels, can also be incorporated into the etching to create unique doors, windows, side panels or over the door top lights.


Also known as a 'transom window' in the U.S, a fanlight is a small semi-circular or rectangular window located above a door or another window.

Frosted glass

Frosted glass is a type of obscure glass that's created with a sandblasting or acid etching technique, most commonly used in bathrooms, offices and front doors. Frosted glass allows light to pass through it, whilst retaining a homeowners privacy by distorting and blurring details; making it semi-transparent.


Window or door furniture refers to the additional aesthetic elements that can be added to enhance its appearance, e.g. ornate window and door handles.


Window or door hardware refers to the elements that make them function properly, e.g. window fasteners and door hinges.

Integral blinds

Blinds that are enclosed in between double or triple glazed windows and doors.

‘Kolorbond’ system

A special coating that forms a molecular bond with the surface of uPVC windows and doors. Guaranteed to last for over 10 years, it is UV and abrasion resistant and doesn’t require repainting.

Marine finish

Although aluminium home improvement products are incredibly resistant to corrosion, an additional marine finish coating can be added to aluminium frames to make them withstand the harshest coastal conditions.

Microporous paint

Microporous paint is a coating used on timber windows and doors, which provides a protective barrier against liquid water, whilst allowing water vapour to past through. This lets the timber breathe.

Overlay stained glass

Overlay stained glass is a modern technique that serves to keep the beautiful ancient art of stained glass alive, in a fraction of the time original stained glass took to produce. The process of creating overlay stained glass involves bonding small coloured glass pieces on to an existing pane of glass, which is then covered with lead strips on both sides of the glass.

PAS 24 accreditation

If a home improvement product has been PAS 24 accredited, it means that it has met rigorous test standards used to assess its security performance.

Powder coating

Powder coatings are used to add colour to metals, e.g. aluminium home improvement products, as powder coatings provide a resilient finish that is considerably tougher than regular paint.

RAL colours

RAL is a colour matching system that defines colours for paint, coatings and plastics across the design industry.

Solar control glazing

A special coating applied to glass that lets the right amount of the sun’s energy in; keeping the space warm in winter and cool in summer.

Tinted glass

Tinted glass is any glass that has had a colour added to it. Tinted glass can be utilised in a number of ways, including increasing privacy, solar control and UV protection.

Thermal break barriers

Used within high quality aluminium, thermal breaks are plastic barriers placed between the inner and outer frame to prevent heat from escaping.


uPVC stands for 'Unplasticized Polyvinyl Chloride'. It is a popular building material due to its durability, weather resistance and low maintenance qualities.

Woodgrain foils

Woodgrain foils are a form of laminate applied to the surface of uPVC, to create a high quality, virtually unbreakable finish.

Woodgrain/wood stain effects

Woodgrain or wood stain effects are a special finish applied to uPVC or aluminium that replicate the look of wood.

Discover our range of windows, doors & conservatories

Our Accreditations

BSI ISO 9001:2015
BS 7412
Fensa Approved Installer
50 years logo
Glass and Glazing Federation
Trading Standards Institute Approved
Ultraframe Installer
The Glazing Arbitration Scheme
NHIC 2018 Winner
The Master Window & Conservatory installers association
QA National Warranties
Back to top