Common garden room terms and phrases: a glossary

We’ve put together a helpful glossary that features all the key words that you are likely to come across when purchasing a timber garden room or orangery.

If you’re considering installing a glazed extension, then you’ve likely come across plenty of industry articles and websites while researching your options. Have you come across any words or phrases you’ve not recognised? What, precisely, is a cupola? Why do rafter cappings seem to be so important? Finally, can anyone please explain the difference between a garden room and an orangery? 

When you’re first starting out, it’s easy to feel overwhelmed with so many industry terms and words to learn. Of course, if you’re working with a professional design and build company like ourselves, you don’t really need to concern yourself with the details as we’ll take care of everything for you. However, many of our clients like to get involved and often find it useful to learn some of the most frequently used words!

Below, you’ll find a useful glossary featuring some of the key words that you are likely to come across. Print off a copy so it’s close to hand as you progress through your home extension project. When building works are finished and you invite your friends to visit, you can impress them with your new-found vocabulary as you give them a tour. 

What’s the difference between an orangery and a garden room?

A garden room, orangery or conservatory can all be classed as a ‘garden room extension’, but the difference can be defined by the proportions of glazing, timber, and masonry materials. 

Orangery: Consisting of semi-glazed walls, an orangery will typically have a roof lantern built on top of a flat roof which lets the natural light stream in. These kind of extensions do not have as much glazing as a conservatory but will still create a bright and airy space. 

Garden Room: A garden room is similar to an orangery with semi-glazed walls, but with a roof made entirely from tiles instead of a roof lantern. A garden room is more likely to look like a part of the building it’s adjoined to rather than an additional add-on, with matching tiles, brickwork, and other details.

Conservatory: A conservatory is predominantly made from glazing. They have a reputation for being hot and stuffy in the summer and cold in the winter. This is a shame, as a quality conservatory traditionally crafted with timber can be a beautiful addition to any home. There are certainly ways to overcome the common temperature problems, such as roof vents which help to improve circulation, underfloor heating and solar control glazing to limit the amount of warmth coming in from the sun.

A – Z Glossary of garden room terms:

Accoya: Accoya® is a revolutionary timber that is created from fast-growing and readily available FSC® or PEFC™ certified tree species, such as Radiata pine. Accoya® is about as durable as wood can be, making it the perfect material for creating eco-friendly garden rooms and orangeries. 

Argon: A dense gas that is used to fill the space between two panes of glass in a double glazed window. Agon-filled windows are highly energy efficient.

Bi-fold doors: Also known as folding sliding doors or folding and stacking door. They open outwards and consist of various door leaves that stack against one another to create an opening. 

Bottom rail: The bottom horizontal rail of a window, with a drip bead that overhangs to ensure no water ingress. 

Bolection mould: A decorative moulding found on doors which projects beyond the face of a panel or frame. Used to enhance panel door designs and the bottom panels on French doors. 

Capping system: The application of aluminium or vinyl sheeting applied to the exterior of a window, door or roof lantern.

Common rafter: Part of a roof lantern. The common rafters run directly up and down from the central ridge to the bottom. The rafters create the main structure which the glazing units sit in. 

Cornice: Decorative framework of a window.

Cupola: A rounded dome structure which is added to a roof or ceiling – usually works well with octagonal roof lantern designs. 

Decorative sash horns: A common external feature on sash windows, which are traditionally included for decorative purposes. 

Door frame: A complete door frame is made up of one header, two jamb legs, and a threshold.

Double doors: Two adjacent doors within a single frame.

Double-hung sash windows: Two sash windows within one frame, both of which can move up and down independently of one another.

Draught gasket: An essential element that ensures a window is sound and draught-proof. They are only visible when the window is open. 

Espagnolette locking system: A flat metal locking system that is typically installed on the vertical frame of a French door or casement window. A handle is attached to a metal rod which is within the window frame and when the handle is turned the system will secure the opening.

Finial: A decorative finish for the top of roof lanterns usually made from solid resin to ensure that it is resistant to the elements. Finials come in a range of shapes so that can be specified to suit homeowners personal tastes, however they also play a functional role and protect the king pin from weathering. We make ours from resin to ensure they don’t crack. 

Foundations: help to provide support to a structure by transferring their weight evenly across the ground and helping them to stay strong and sturdy. 

French casement windows: Similar to a standard casement window, these designs are made without the central mullion, creating a clear and unobstructed view when opened. They can be often used for second floor dormer windows or for first floor windows where the opening is not large enough to meet current escape regulations. 

French doors: Similar in appearance to a French window, these classic glazed doors come in pairs and traditionally open outwards to give access to balconies, patios, and other external areas. When open, they create one large opening with no disruptions to the view outside. 

FSC: A worldwide certification system that allows businesses and consumers to use sustainable timber products. It assesses a timber’s chain of custody and the way the forest it has been sourced from is managed. 

Gables: A side or front wall of a property with a triangular shape at the top, created by a sloping pitched roof. 

Gunstock style: A style of door panel, when the stiles change in size as they go down the door.

Glazing bar: Bars that run between adjacent panes of glass in a window, adding to the fenestration of the window and the design’s style.

Glazing bead: This ensures that water does not ingress between the timber joints in a window – we make ours from Accoya with a secret stainless steel fixing, which is then sealed with a silicon bead. 

Hip and rafter cappings: Powder-coated sections with aluminium cladding that hold the glass panes in place and ensure a roof lantern is watertight. 

Hip rafter: A key structural component that spans from the corner of the roof lantern to the ridge.

Ironmongery: A wider term for any kind of door or window hardware, also known as architectural hardware. This includes everything from handles and locks to window hinges. 

Jack rafter: Part of a roof lantern. As opposed to the common rafters, the jack rafters run at an angle in the corners of the roof lantern, giving additional support to the sides. The rafters create the main structure which the glazing units sit in. 

Jamb: The side post of a casement window. 

Kerb: An upstand that a roof lantern will sit on, which has the flat roof membrane tucked inside to ensure the whole structure is waterproof. 

Kingpin: A laminated timber section on a roof lantern, which connects the hip rafters to the ridge. It will usually have a finial fixed to the top. 

Loggia: An outdoor corridor or gallery with a fully covered roof and an outer wall that is open to the elements. 

Low E coating: Low emissivity, meaning a surface which emits low levels of radiant heat.

Meeting rail: The middle horizontal rail where two sashes meet when a sash window is fully closed. Will include a draught excluder. 

Microporous paint: A paint which allows water vapour to pass through it, but acts as a barrier to liquids.

Moulding: Also known as casing, it is used to trim the perimeter of windows and doors for a decorative finish.

Parapet: Where the side wall extends slightly above the level of a flat roof, creating a low barrier.

Pitch: Measured in degrees, a roof’s pitch is the steepness of the roof. The pitch is calculated by dividing the vertical rise by the horizontal span of the roof.

Pool House: A pool house can serve several purposes, either providing cover for your pool or to act as a nearby summer house or changing facility.

Rafter cappings: Protective ‘caps’ which are fitted over the rafters of a roof lantern to protect them from the external elements, giving them longevity. We make ours from aluminium, which is a particularly strong material. 

Raised and fielded panel: An attractive, decorative panel with grooved edges and a fielded or moulded element to its face – entrance doors will often have anything from two to six panels depending on their style. 

Redwood: This is a slow-growing timber, which gives an aesthetically pleasing, smooth grain. It’s attractive grain makes it ideal for using on the interior of a garden room, resulting in an exceptional moulded and painted finish. 

Ridge cap: The central member which runs along the top length of a roof lantern, at its highest point. Where the two sides join in the middle.  

Roof lantern: A glass skylight that is built upon a flat roof to add height to a ceiling and allow natural light to enter the room below.

Sash windows: A window with two moveable sashes, with one sitting in front of the other. They bring a traditional, classic aesthetic to a home. They are available with the traditional cord and weights, or can be spring balanced for a modern touch. 

Slave leaf: A locking system applied to French doors and windows, to allow for the use of one handle. The slave left is the door that is often fixed in place and used less regularly. 

Spring sash window: A sash window which uses a spring-loaded device used for counterbalance.

Staff bead: The detailed trim that frames your sash box and keeps the sashes in place within the sash box. 

Teknos: An innovative paint brand that has developed a microporous paint system, which enhanced the longevity of timber products. Their paint is made from a blend of water and plastic, resulting in a highly durable and protective layer of paint once dry.

Threshold: A strip of wood that forms the bottom of a doorway, which is crossed when entering a house or room. Usually made from a durable hardwood to withstand the footfall. 

Top hung sash: The uppermost window within a frame.

Top rail: The top horizontal rail of a window.

U-Values: A number used to measure the energy efficiency of a door or window. The lower the number, the better the insulation. It’s advised that you look out for the whole product U-Value, rather than just the central pane U-Value. 

Vent: A timber glazed sash window with an aluminium shroud that is installed in a roof lantern to help ventilate the room. They can be powered by an electric motor and can include rain sensors and thermostats.

Warm edge spacer bar: Insulation applied to the edges of a window which keeps the panes of glass apart and reduces the amount of heat lost through a sealed unit.

Weatherstripping: The process of sealing openings such as doors and windows from the elements.