Conservatory vs Orangery vs Extension: Which to Build?

When you want more space and more light at the back of your home, three options dominate the shortlist: a conservatory, an orangery or a full extension. The conservatory vs orangery vs extension decision shapes your budget, how the room feels through the seasons, and what permissions you need, so it is worth understanding the real differences before you call a builder. This guide explains how each one is built, what they cost in broad terms, how they perform in winter and summer, and the planning and building regulations that apply, with notes for homeowners here in Kent.

Table of Contents

The quick difference between the three

In simple terms, the three sit on a spectrum from mostly glass to mostly solid wall:

Conservatory: predominantly glazed walls and a glazed or polycarbonate roof, the lightest and usually cheapest option, and traditionally the coldest in winter and hottest in summer.
Orangery: a hybrid with substantial brick or stone pillars, a flat perimeter roof and a glazed lantern in the centre, giving a more solid, room-like feel than a conservatory.
Extension: a fully built structure with solid walls and a conventional roof, indistinguishable from the rest of the house and the most expensive but most usable year-round.

The more glass and the less solid wall, generally the lower the cost and the more the temperature swings with the weather.

Conservatories: light, airy and the most affordable

A conservatory is built largely from glazing on a low brick base, with a roof of glass or polycarbonate. It is the fastest and cheapest way to add a bright garden room, and modern glazing performs far better than the older designs that became unbearable in July and freezing in January. It remains, though, the option most affected by the weather, so heating and the right glass specification matter if you want to use it all year.

A major appeal is that conservatories are often exempt from building regulations. According to the Planning Portal, a conservatory is normally exempt when it is built at ground level and under 30 square metres in floor area, is separated from the house by external-quality walls, doors or windows, has an independent heating system with its own on and off and temperature controls, and where the glazing and any electrics meet the relevant standards. That exemption is a big part of why conservatories are cheaper and quicker to build.

Orangeries: a more solid, room-like feel

An orangery sits between a conservatory and an extension. It uses more brick or stone, typically with columns or piers at the corners, a flat roof around the perimeter and a glazed roof lantern that floods the centre with light. The result feels more like a genuine room of the house than a conservatory does, with wall space for radiators, kitchen units or shelving, while still being notably brighter than a standard extension.

That extra masonry brings better insulation and a more stable temperature than an all-glass conservatory, at a cost that sits above a conservatory but usually below a full extension of the same size. Because an orangery has more solid roof and wall than a conservatory, it is more likely to need building regulations approval, so it is worth confirming early with your builder or building control.

Extensions: maximum space and year-round comfort

A full extension is a permanent part of the house with solid, insulated walls and a tiled or flat roof. It is the most expensive of the three for a given footprint, but it is also the most comfortable to use in every season and the most flexible, since it can become a kitchen, a family room, a bedroom or anything else without compromise. For many homeowners adding real living space and resale value, an extension is the option that pays back best despite the higher outlay.

Extensions almost always require full building regulations approval, and depending on size and position they may need planning permission, though many fall under permitted development. The build takes longer and is more disruptive than a conservatory, so plan around that.

Planning permission: what to check

All three can often be built without a planning application under permitted development, but the limits matter and they are not identical for every home. Permitted development sets restrictions on how far a single-storey rear addition can project, on height, and on how close it sits to boundaries, and those allowances are reduced or removed for flats, maisonettes, listed buildings and homes in conservation areas. A large or two-storey extension is more likely to need a full application than a modest conservatory. The safest approach is to confirm your specific limits before you design the room, either through your local authority or by applying for a lawful development certificate, which gives you written proof the work is permitted. Getting this right early avoids the costly mistake of building something that later needs retrospective permission, and it is worth doing whichever of the three you choose.

Cost, comfort and how to choose

Cost rises as you move from conservatory to orangery to extension, and so does year-round usability. A useful way to choose is to start from how you will use the room:

Choose a conservatory if budget is the priority, you want maximum light, and you mainly need a bright garden room rather than a fully integrated everyday space.
Choose an orangery if you want a brighter-than-average room that still feels solid and warm, with wall space for furniture, and you can stretch beyond a conservatory budget.
Choose an extension if you want genuine, fully usable living space that matches the house, adds the most value, and works in every season, and your budget allows.

Whichever you pick, get the glazing specification and heating right, as that is what determines whether the room is used in February or shut off until spring. For tailored advice and quotes across Kent, see the Contemporary Structures homepage.

Frequently asked questions

What is the difference between a conservatory and an orangery?

A conservatory is mostly glass with a glazed or polycarbonate roof, while an orangery uses more brick or stone with a flat perimeter roof and a central glazed lantern. The orangery feels more like a solid room, holds heat better and costs more than a comparable conservatory.

Is a conservatory cheaper than an extension?

Yes, for the same footprint a conservatory is usually the cheapest of the three because it uses less masonry and is often exempt from building regulations. An extension costs the most but gives fully usable, year-round living space.

Do you need building regulations for a conservatory?

Often not. A conservatory is normally exempt when it is at ground level, under 30 square metres, separated from the house by external doors or windows, has its own independent heating controls and meets the glazing and electrical standards. An orangery or extension is more likely to need approval.

Which adds the most value to a home?

A well-built extension generally adds the most value because it provides permanent, fully usable living space that matches the rest of the house. An orangery can add good value too, while a conservatory adds the least but at the lowest cost.

Can I use any of them all year round?

An extension is comfortable in every season by default. An orangery performs well with its mix of solid wall and glazing. A conservatory can be used year-round if it has modern, well-specified glazing and adequate heating, but it is the most affected by hot and cold weather.

Conservatory vs Orangery vs Extension: Which to Build?

The quick difference between the three

Conservatories: light, airy and the most affordable

Orangeries: a more solid, room-like feel

Extensions: maximum space and year-round comfort

Planning permission: what to check

Cost, comfort and how to choose

Frequently asked questions

What is the difference between a conservatory and an orangery?

Is a conservatory cheaper than an extension?

Do you need building regulations for a conservatory?

Which adds the most value to a home?

Can I use any of them all year round?

Related guides