For most UK homeowners, a conservatory is cheaper to build than a conventional house extension. The gap can be substantial because a conservatory often uses a simpler structure, more pre-designed components and less complex internal work. However, the cheapest option on paper is not always the best value once heating, insulation, year-round comfort and future alterations are taken into account.
A small uPVC conservatory may cost considerably less than a fully integrated extension, while a large bespoke conservatory with insulated solid walls, a tiled roof and high-performance glazing can approach the price of a modest extension. Your choice should therefore be based on how you want to use the room, not only on the initial quotation.
This article compares the main costs, practical limitations and long-term considerations so you can make a better-informed decision before speaking to builders or conservatory installers.
Is a conservatory cheaper than an extension?
Usually, yes. A conservatory is generally cheaper because its design is often based around a standard footprint, manufactured frames and a glazed roof or modular solid roof system. A traditional extension normally involves more extensive brickwork, structural calculations, roof construction, insulation and internal finishing.
As a broad UK guide, a basic conservatory may start at around £10,000 to £20,000, depending on its size, shape, materials and specification. A mid-range conservatory designed for comfortable use throughout the year may cost roughly £20,000 to £40,000 or more.
House extensions commonly begin at a higher level, often around £35,000 for a relatively straightforward single-storey project, with many projects reaching £60,000 to £100,000 or more. London and other high-cost areas can be considerably more expensive, while difficult access, drainage changes and complex structural work can raise costs anywhere in the country.
These figures are only starting points rather than quotations. VAT, professional fees, ground conditions, kitchen or utility-room connections, heating upgrades and decorating may not be included in an initial headline price.
Why conservatories tend to cost less
The main financial advantage of a conservatory comes from its construction method. Many conservatories are supplied as coordinated kits, allowing the frame, roof, glazing and doors to be manufactured together before being installed on site.
A conventional extension is more likely to require several separate trades and a longer programme. It may involve blockwork, external brick matching, a new roof, steel beams, plastering, electrics, plumbing and extensive making-good inside the existing house.
Conservatories can also benefit from lighter construction, although this does not mean that foundations can be ignored. The required base still depends on the ground, the structure, nearby trees, drainage and the weight of the roof system.
Another saving may come from planning. Many conservatories can be built under permitted development rights if they meet the relevant conditions, whereas an extension may require a planning application. Neither route should be assumed without checking the rules for your property, particularly if you live in a conservation area, a listed building or a designated area.
For a useful overview of the construction process, see this explanation of how to construct a conservatory, including foundations, glazing, insulation and final checks.
What does a conservatory cost?
The size and style make the biggest difference to the starting price. A small lean-to is usually more affordable than a large Victorian, Edwardian or P-shaped design because it has fewer corners and a simpler roof arrangement.
Material choice also affects the budget. uPVC is often the least expensive frame material and requires relatively little maintenance. Aluminium can provide slim sightlines and a modern appearance, but the specification, thermal performance and finish can increase the price; a detailed guide to aluminium conservatory costs can help when comparing quotations.
Timber offers a traditional appearance and can work particularly well with period properties, although it usually requires more maintenance and careful detailing. An oak structure, for example, is a premium choice rather than a budget alternative, especially when craftsmanship and bespoke joinery are involved.
The roof is another major cost. A simple glazed roof may be less expensive initially, but a high-quality roof must manage solar gain, ventilation and heat loss. Solid or tiled roofs can improve comfort and appearance, but they add structural weight and may require additional calculations or strengthening.
- Frame material and colour finish
- Roof type, insulation and ventilation
- Glass specification and solar-control features
- Door design, opening style and security hardware
- Flooring, plastering, lighting and heating
- Foundations, drainage and access to the site
Do not compare quotes solely by the external dimensions. Two conservatories with the same footprint can differ significantly in price if one includes upgraded glass, insulated columns, a warm roof, underfloor heating and internal plastering.
What does a house extension cost?
An extension is normally more expensive because it is treated as part of the main house rather than as a separate lightweight addition. The new room needs to meet the same standards for insulation, structural stability, fire safety and weather resistance as the existing building.
Costs can rise quickly when the extension includes a kitchen, utility room or bathroom. Plumbing and electrical work are more involved, and a kitchen extension may require cabinetry, worktops, appliances, lighting design and changes to the existing layout.
The connection between the new and old parts of the house is also important. Builders may need to remove an external wall, install steel beams, reroute services and repair ceilings, floors and decorations. These items are easy to overlook when a homeowner focuses on the cost per square metre.
Groundworks can be another significant expense. Poor soil, sloping land, tree roots, a high water table or nearby drains may require deeper foundations or specialist solutions. A reputable contractor should identify these risks before providing a firm price, rather than hiding them inside vague provisional sums.
Which option gives more usable space?
An extension generally provides more consistent year-round space. Its roof, walls and windows can be designed to match the thermal performance of the existing house, making it easier to use as a dining room, kitchen, living room, home office or bedroom.
A modern conservatory can also be comfortable throughout the year, but the specification matters. Large areas of glass can cause overheating in summer and heat loss in winter if the glazing, shading, ventilation and heating are poorly designed.
Older conservatories with basic polycarbonate roofs are often the least comfortable. Replacing the roof may improve the room, although it is important to check the existing frames, foundations and ventilation before assuming that a roof conversion is suitable.
Consider how often the room will be used. If you want a bright occasional sitting room or a garden-facing dining area, a conservatory may meet your needs at a lower cost. If you need a stable-temperature workspace or a permanent kitchen, an extension may offer better long-term value.
Planning permission and building regulations
Planning permission and building regulations are separate matters. A project may be permitted development but still need to comply with building regulations, especially where structural alterations, foundations, drainage or changes to the external wall are involved.
Conservatories are sometimes exempt from certain building regulation requirements when they meet conditions such as a maximum floor area, separation from the house by suitable doors and independent heating controls. The exact rules depend on the project, so professional advice is sensible before work begins.
Extensions usually require building regulations approval. This covers matters such as foundations, insulation, ventilation, structural openings, electrics, drainage and fire safety. A building control officer or approved inspector may need to inspect key stages of the work.
Do not treat approval as an administrative extra. Missing paperwork can complicate a future sale, affect insurance questions and make it harder to prove that the work was completed properly.
Hidden costs that can change the comparison
The initial price difference may narrow when all associated work is included. Conservatory quotes sometimes exclude the removal of an existing structure, internal plastering, flooring, decoration, electrical upgrades or connection to the central heating system.
Extensions can have even more variable costs because the design is less standardised. A quotation should explain whether it includes architectural drawings, structural engineering, planning charges, building control, waste removal, scaffolding, drainage alterations and VAT.
Ask each contractor to specify the following items clearly:
- Demolition and removal of existing patios or structures
- Excavation, foundations and disposal of soil
- Drainage surveys and any diversion work
- Windows, doors, rooflights and external finishes
- Insulation levels and the method of heating the room
- Flooring, plastering, painting and final cleaning
Keep a contingency budget as well. Around 10 to 15 per cent may be sensible for an uncomplicated project, while older properties and uncertain ground conditions may justify more. A contingency is not a licence for poor estimating; it is protection against genuinely unforeseen work.
Common mistakes homeowners make
The most common mistake is choosing a conservatory only because it is cheaper, then discovering that it does not perform as expected. A low-cost room that is too hot in July and too cold in January may require later spending on blinds, heating, roof replacement and insulation.
Another mistake is choosing the largest possible footprint without considering garden access, light levels and the relationship with neighbouring properties. A smaller, well-designed room can feel more useful than a larger space that is awkwardly connected to the house.
Some homeowners also accept a quotation without confirming the specification. Terms such as “energy-efficient glass” or “insulated roof” are not enough on their own; ask what products are included, what insulation values apply and how ventilation will be provided.
It is also unwise to compare a conservatory quote that includes only the shell with an extension quote that includes full internal finishing. Request like-for-like prices so that the apparent saving is meaningful.
How to choose the better-value option
Start with the purpose of the room and the number of months each year you expect to use it. A conservatory is often the better financial choice when you want a relatively simple addition with plenty of daylight and a strong connection to the garden.
An extension may be better value when it will replace an undersized kitchen, add a bathroom or create permanent living space. It can also offer more flexibility for furniture and internal layout because the walls and roof do not need to be dominated by glazing.
Look at the quality of the connection to the house. A well-designed threshold, suitable ventilation, effective shading and correctly sized heating system can make a conservatory feel integrated rather than attached as an afterthought.
For projects that combine different materials or need to match an unusual property, a bespoke conservatory design may solve practical and aesthetic problems, although bespoke work normally costs more than a standard package.
Obtain at least three detailed quotations and check the contractors’ experience with similar projects. Ask to see examples of completed work, confirm who will manage building control and establish how variations will be priced before signing a contract.
What We Get Asked…
Is a conservatory always cheaper than an extension?
Not always. A small standard conservatory is usually cheaper, but a large bespoke design with premium glazing, a tiled roof, complex foundations and extensive internal work can cost as much as a straightforward extension.
Can a conservatory be used all year?
Yes, provided it has suitable insulation, glazing, ventilation, shading and heating. The design should address both winter heat loss and summer overheating rather than concentrating on one season.
Does a conservatory add as much value as an extension?
Market value depends on the property, local demand and the quality of the work. An extension may appeal to more buyers because it provides permanent house-standard accommodation, but a well-designed conservatory can still improve enjoyment and saleability.
Do conservatories need planning permission?
Some fall within permitted development rules, but restrictions apply and exemptions are not automatic. Check the size, position, property history and local designations before ordering materials.
Should I choose a solid conservatory roof?
A solid roof can improve insulation and reduce glare, but it adds weight and may affect the structure, foundations and building regulation position. Have the existing conservatory assessed before committing to a conversion.
Our Final Thoughts
A conservatory is normally the cheaper route to additional space, particularly when you choose a straightforward design and keep the specification proportionate. An extension costs more, but it may provide better thermal performance, greater flexibility and stronger long-term usefulness for a kitchen, office or main living area.
The right decision comes down to the room you need rather than the cheapest headline price. Compare complete specifications, allow for professional and finishing costs, and make sure planning, building regulations and ground conditions have been properly considered.
If you are ready to investigate your options, begin by measuring the available space and writing down how the room will be used in summer and winter. You can then discuss a realistic brief with experienced installers and compare it with the cost of a fully finished extension, rather than making a decision based on a basic shell price.
