There was a time when conservatories and extensions occupied very different territory – different budgets, different build methods and different expectations for how the finished space would feel.
But that’s less true now than it used to be.
Modern conservatories, particularly those built with energy-efficient roofing options and dwarf walls, can now deliver much of what a traditional extension offers – while typically costing less and taking far less time to build.
Whichever way you frame the conservatory vs extension question, the real answer for most homeowners isn’t which structure is better outright – it’s which combination of cost, time, disruption and layout actually suits their home and budget.
This guide compares conservatories and extensions across the factors that matter most, including cost, build time, planning permission, everyday comfort, property value and natural light.
Is a conservatory a type of extension?
In many cases, yes – a well-specified modern conservatory can look and perform much like a traditional extension of the home.
The original distinction was mostly about the roof and walls but, today, conservatory features like high-performance glazed roofing, dwarf walls finished in brick to match your existing property, and modern sliding or bi-fold doors all challenge this.
Together, they create a conservatory that looks and performs like a natural continuation of the house, rather than an addition.
Because every conservatory is made to measure, these details can be specified to suit your own property rather than a standard design – you can see the range of options across our conservatory styles.
Where a conservatory and an extension differ most now is layout flexibility.
An extension suits an entirely new room type – a bedroom or bathroom, for example – in a way a conservatory typically doesn’t need to.
A conservatory suits living space – a dining room, lounge or home office (or flexible combination which can be adapted) – and can match what an extension offers for that kind of room, often with a brighter, more open feel.
The line between a conservatory and extension becomes blurred when changes are made to its structure or how it connects to the main house. Your conservatory may be classified as an extension if:
- It exceeds the size limits permitted without planning permission;
- It features a solid roof, instead of a glass or polycarbonate one;
- You remove the external doors or walls that separate it from your home, creating an open-plan layout;
- It doesn’t meet certain building regulations, such as insulation or structural stability.
In these cases, planning permission may be needed, and the structure would be treated as a traditional extension.
Cost and build time
A conservatory typically costs significantly less than a traditional extension of a similar size – and is usually installed in days rather than months.
Most conservatory projects fall somewhere between £9,000 and £25,000, compared to £30,000–£50,000 or more for a single-storey extension – though costs vary considerably depending on size, specification and location, so treat these figures as a general guide rather than a quote.
Much of that difference comes down to build time and labour. With a prefabricated foundation system like ConservaBase, the full build for most conservatory styles can often be completed in as little as four to six days.
This is compared to several weeks or months for a traditional extension once groundworks, brickwork and internal finishing are accounted for.
| Factor | Conservatory | Traditional extension |
| Cost | Typically £9,000–£25,000* | From around £30,000–£50,000+* |
| Build time | Can be as little as four to six days for the full build | Typically several weeks to a few months |
| Disruption | Lower – modular build, minimal groundworks | Higher – full building work, extended access |
| Planning permission | Often falls under Permitted Development Rights, subject to size and design | Frequently required, depending on size and design |
| Property value | Can add meaningful value, particularly when well integrated with the home | Can add meaningful value, particularly when adding a new room type |
| Natural light | High, particularly if opting for extensive glazing | Lower, limited to window openings |
*Costs are indicative and vary by project — use the ConservatoryLand Quote Builder for a figure based on adding a conservatory to your own home.
Planning permission
Many conservatories fall under Permitted Development Rights, meaning planning permission often isn’t required – but this depends on your property and design, so it’s worth checking rather than assuming.
As a general guide, permitted development limits are usually based on how much of your property’s total area the new structure covers.
Other rules can apply too, covering roof height and position. Under Building Regulations, you may also need to consider whether you’re removing the external wall between the new space and the house.
Rules may also be subject to additional local restrictions and your home’s history of previous extensions counts towards the overall limits, so it’s worth confirming your own project’s status before finalising plans.
If you’re considering a solid or tiled roof design specifically, our guide to planning permission for a solid roof conservatory covers this in more detail.
Extensions, on the other hand, need Building Regulations approval and are more likely to need planning permission, largely because of their size and the structural changes they often involve.
Myth vs reality: comfort and property value
The idea that conservatories are too hot in summer and too cold in winter comes from notions surrounding older, outdated designs – not a fair description of a well-specified conservatory today.
Solar control glazing, self-cleaning roof glass and modern roofing options have addressed this, making a well-specified conservatory comfortable to use across the year. This also helps with energy efficiency day-to-day.
Furthermore, both a conservatory and an extension can add value to a home. A conservatory that’s well integrated with the existing property is more likely to read as a natural part of the house rather than a separate addition.
Natural light and the feel of the space
A conservatory typically lets in significantly more natural light than an extension, thanks to its extensive glazing.
Extensions, meanwhile, rely on standard window openings, so light levels depend on how many windows are included and where they sit.
A conservatory is built with glazing on multiple sides, so the room often stays brighter for more of the day – which is one of the main reasons people choose them as everyday living space rather than just occasional use.
If you’re planning how to use the extra space, our guide to ways to use your conservatory has more ideas – and if a garden room is also on your shortlist, our comparison of garden rooms vs conservatories is worth reading alongside this one.
Frequently asked questions
How much can I extend my house without planning permission?
Under Permitted Development Rights, a single-storey rear conservatory can extend up to four metres beyond the rear wall of a detached house, or three metres for semi-detached and terraced properties – though larger limits may apply through a prior approval route.
Side extensions can’t exceed four metres in height or half the width of the original house. These limits apply to the total of all extensions, including any added by previous owners, so it’s worth checking your starting position. Our guide to conservatory planning permission has more detail.
How long does a conservatory take to build?
With ConservaBase, ConservatoryLand’s prefabricated foundation system, most conservatory styles can be completed in as little as four to six days. Build times vary depending on size, style and site conditions, but the process is significantly quicker than a traditional extension. For a fuller breakdown, see our guide to estimated conservatory build times.
How much does a conservatory cost compared to an extension?
Most conservatory projects fall between £9,000 and £25,000, compared to £30,000–£50,000 or more for a single-storey extension – though both vary depending on size, specification and location. Conservatories also tend to involve lower labour costs, since the build is shorter and less complex. Use the Quote Builder for a price based on your own project, or see our conservatory price guide for more detail.
Do I need foundations for a conservatory?
Yes – every conservatory needs a stable base. ConservatoryLand uses ConservaBase, a prefabricated steel foundation system that replaces traditional strip foundations and significantly reduces the groundwork phase of the build. For more information, see our guide to conservatory foundations.
Which is right for you?
If cost, speed and disruption matter most, a conservatory is usually the stronger choice. If you need an entirely new room type, such as a bedroom or bathroom, an extension is likely the better fit.
For most homeowners adding living space rather than a specific new room, a modern conservatory can match much of what an extension provides – at a lower cost and with far less disruption.
Start designing your own with our online Quote Builder to see a personalised layout and price in minutes, or call us on 0800 952 8000 to talk through your options.
Disclaimer
Please note that the information provided on this page is not legal advice. It is given as a guide only, based on the information outlined at planningportal.co.uk.
The guidance described on this page applies to houses, not flats, maisonettes or other buildings. Other consents may also be required if your home is listed or in a designated area.
The information was correct at the time of publication, but it is subject to change as a result of legislative changes. Before beginning any work, always seek advice from local planning authorities.
