Updated: August 2026
Summary
- The price of a conservatory varies significantly depending on the material chosen (aluminium, wood, PVC) and the surface area built, with costs often ranging from one to three times as much for the same surface area.
- A conservatory is only considered living space, and valued as such, if it is properly insulated, heated and connected to the rest of the home; otherwise, it remains an ancillary space.
- The impact on resale value depends less on the conservatory itself than on the quality of its construction: well insulated and bright, it appeals to buyers; poorly designed, it may be perceived as a source of future expenses.
- Above 20 m² of floor area (or 5 m² depending on the area and the local PLU), building a conservatory requires planning permission; below this threshold, a prior declaration of works is generally sufficient.
- Investing in a conservatory before a sale is only profitable if the property objectively lacked living space, and if the work is completed well before the property is put on the market.
- In a property listing, it is better to present a conservatory for what it genuinely offers (natural light, additional square metres, specific use) rather than overvalue it without technical evidence of its insulation.
Introduction
You are considering building a conservatory, or you already have one, and you are wondering whether this investment will result in added value when you resell your house. Conservatories have long been seen as additional, bright and pleasant living spaces, but if poorly designed, they can also become a weak point in a property listing, or even a negotiating argument for the buyer.
The reality lies somewhere between these two extremes. A well-built conservatory, properly insulated and harmoniously integrated into the house, can be a genuine selling point. But an ageing, poorly insulated conservatory, or one built without authorisation, may instead concern a buyer, who will anticipate renovation work or excessive heating costs. It all comes down to construction quality, administrative compliance and presentation.
This article reviews the average price of a conservatory depending on the materials and surface area, the distinction between living space and ancillary space, the actual impact on resale value, the administrative procedures, and the key question of whether the investment is profitable before a sale. You will also find advice on how to present an existing conservatory effectively in a property listing, and why it may be useful to call on a local Capifrance real estate advisor to objectively assess the impact of this improvement on your property.
The Price of a Conservatory: What Affects the Budget?
The Material, the Main Cost Factor
The choice of structural material is a determining factor in the final price of a conservatory. PVC is generally the most affordable option: it provides good basic insulation and requires little maintenance, but offers more limited customisation possibilities for large openings. Aluminium allows for slimmer profiles and wider openings, creating a look often considered more modern, at a mid-range to higher price. Finally, wood appeals for its character, particularly on older houses, but generally requires a higher budget and regular maintenance (treatment, wood stain).
For an equivalent surface area, PVC generally remains the most economical option, aluminium falls within an intermediate price range, and wood (or wood-aluminium, an increasingly common hybrid solution) tends towards the high end of the market. These differences are explained by the cost of raw materials and the expertise required for installation.
Surface Area, Configuration and Additional Costs
The larger the conservatory, the higher the cost, although not in a strictly proportional way: some expenses (connections, foundations, opening up the existing wall) are partly fixed, which slightly reduces the price per square metre for larger surface areas. The configuration also matters: a simple conservatory built against a load-bearing wall generally costs less than a corner conservatory or a flat-roof extension with an overhead glass roof. The type of roof and the quality of the glazing (double or triple glazing, UV protection) also have a significant impact on the budget.
For example, for a property worth €300,000, a medium-sized conservatory represents an investment that can range, depending on these criteria, from a modest fraction to a significant percentage of the property's value. Additional costs must also be taken into account: foundation slab (often the most expensive item after the structure), electrical connections and potentially heating, installation of external blinds to prevent overheating, and administrative application fees—costs that are often underestimated when the estimate is based solely on the price of the structure.
Conservatory and Living Space: An Essential Distinction
The Definition of Living Space
A room is only considered living space if it meets certain criteria: sufficient ceiling height, the possibility of being used all year round, and above all, a level of thermal insulation compatible with permanent occupation. This last point is what distinguishes a conservatory used as a “living room” from a conservatory used as a “buffer space”. Built with high-performance materials (double or triple glazing, reinforced roof insulation, suitable heating), it can be included in the property's living space, which has a direct impact on its value. Conversely, a conservatory with single glazing may be pleasant in spring or autumn, but difficult to use in winter or during very hot weather: it is therefore not counted as living space, and its value is closer to that of a covered terrace.
Why This Point Is Decisive for Resale Value
This distinction directly determines the sales pitch. A buyer, or their advisor, will systematically want to know whether the conservatory is insulated and heated. An up-to-date Energy Performance Certificate (DPE), including the conservatory in the calculation if it is heated, helps remove this uncertainty. It is therefore essential, if the objective is to increase the property's value over time, to invest in quality insulation from the outset: the initial additional cost, often around 15 to 30% compared with a standard conservatory, is generally recouped at the time of resale.
The Actual Impact of a Conservatory on a House’s Value
The Benefits Perceived by Buyers
A well-designed conservatory provides natural light, an increasingly sought-after feature, as well as additional living space (dining room, office, additional lounge) that can compensate for limited space elsewhere in the house. It also creates a pleasant transition between the interior and the garden, a feature that particularly appeals to families. These elements can genuinely make a difference compared with similar properties without this type of improvement. To compare your project with what is available on the local market, Capifrance property listings allow you to identify properties that highlight this type of feature.
The Risks of Loss of Value to Be Aware Of
Conversely, a poorly designed conservatory can have a negative impact. The main criticism of older conservatories concerns the risk of overheating in summer (greenhouse effect with a south-facing exposure and no sun protection) and heat loss in winter. An informed buyer will be able to identify these warning signs: single glazing, absence of solar shading, ageing structure, signs of damp. This may lead to a request for a price reduction, or even cause the property to be removed from consideration if the conservatory is perceived as a “dead” space. A conservatory that does not comply with planning regulations may even constitute a legal obstacle to the sale: this point must be checked before the property is put on the market. The impact must also always be considered in relation to the local market: in an area where conservatories are uncommon, this feature may be a genuine differentiator; elsewhere, its effect will be more limited. A free online property valuation provides an initial idea of how the local market values this type of improvement.
Administrative Procedures to Be Aware of Before Building
Prior Declaration or Planning Permission
For a conservatory with a floor area between 5 and 20 m², a prior declaration of works is generally sufficient. This application, submitted to the local town hall, includes a location plan, site plan, representation of the façade and a description of the materials. The processing time is generally one month. Above 20 m² of floor area, or 5 m² in certain areas where the local PLU lowers this threshold, planning permission becomes necessary, with a more comprehensive application and a processing time often ranging from two to three months. Using an architect may also become mandatory if the total surface area of the house after the extension exceeds the legal threshold in force.
The Consequences of an Undeclared Construction
Building a conservatory without authorisation, or without complying with the authorisation obtained, exposes you to several risks: an order to regularise or demolish the structure, an increase in development tax and, above all, a potential obstacle when selling. As part of the planning compliance checks, the notary may require the situation to be regularised before finalising the deed, which can delay the transaction or even cause it to fall through if the buyer withdraws. It is therefore advisable, before putting the property on the market, to check that the conservatory has received all the required authorisations and to regularise the situation if necessary.
When Is Investing in a Conservatory Profitable Before a Sale?
Situations Where a Conservatory Is a Genuine Asset
The investment is most likely to be profitable when the house objectively lacks living space: limited living space or the absence of a separate dining room. The conservatory then fills a genuine need that is noticeable to all buyers, rather than simply providing an aesthetic feature. This is also the case when the plot and orientation naturally lend themselves to such an extension, and when the work is completed sufficiently early before the property is put on the market for the conservatory to appear fully integrated into the everyday use of the house. It can then become a selling point comparable to other improvements that increase a house's value before a sale, such as converting an attic before a sale to create additional living space, or the impact of a garage or carport on the overall perception of the property: in all cases, it is the consistency between the investment and the actual identified need that determines the profitability of the project.
Situations Where the Investment Is Not Justified
Conversely, building a conservatory solely with the aim of reselling the property at a higher price, when the property does not objectively need one, is rarely profitable in the short term. The return on investment rarely reaches 100% of the amount invested, particularly if the work is carried out in a rush just before the property is put on the market. This is especially the case when the available budget only allows for a basic, poorly insulated conservatory, which will be perceived as a secondary space or even a point of concern, or when the property already has sufficient living space. In these situations, it is often wiser to allocate the budget to improvements that are more universally valued (energy renovation, kitchen, bathroom). A local real estate advisor, in constant contact with the market, can help identify the improvements that offer the best ratio between investment and increase in value.
How to Present an Existing Conservatory in a Property Listing
Highlight the Real Benefits, Without Exaggerating
It is recommended to describe precisely how the conservatory is used on a daily basis (dining room, office, additional lounge), its surface area, its exposure and its technical characteristics if they are favourable: type of glazing, heating and roof insulation. This concrete information reassures buyers and helps them imagine themselves using the space, rather than wondering about potential defects that have not been mentioned. It is also useful to specify whether the conservatory is included in the property's declared living space or whether it is an unheated ancillary space, to avoid downward negotiations resulting from a late discovery.
Pay Attention to the Visual Presentation and Rely on a Professional
Photographs play a central role: a bright, tidy room with an unobstructed view of the garden immediately creates a positive impression of the additional space. Conversely, backlit photos or images highlighting ageing equipment can negatively affect the perception of the property. An experienced real estate advisor will know how best to present a conservatory according to the type of buyers being targeted and can help you objectively assess its actual added value compared with similar properties without a conservatory. This approach is similar to the one used for other specific property configurations, for example when it comes to enhancing the value of a property without outdoor space: in both cases, the ability to highlight the property's genuine strengths without concealing its limitations is what allows for the best possible valuation
Contact a Capifrance Real Estate Advisor
Accurately assessing the impact of a conservatory on the value of a house requires good knowledge of the local market and buyers' expectations in your area. A Capifrance real estate advisor can visit your property, assess the construction quality and insulation of your conservatory, check the administrative compliance of the improvement and tell you whether this feature genuinely adds value in the context of your sale. They can also advise you on the most effective presentation strategy and support you through every stage of your house sale with Capifrance, from the initial valuation through to signing the final deed.
Conclusion
- The price of a conservatory varies significantly depending on the material (PVC, aluminium or wood) and the surface area built, as well as additional costs such as foundations and connections.
- A conservatory is only valued as living space if it is genuinely insulated and heated for year-round use; otherwise, it remains an additional space with more limited value.
- The impact on resale value depends primarily on construction quality: bright and well insulated, it appeals to buyers; poorly designed, it may raise concerns about overheating or heat loss.
- Depending on the surface area, either a prior declaration or planning permission is required; the absence of authorisation can block the sale when the notary checks compliance.
- The investment is only genuinely profitable if the property objectively lacked living space and the work is completed well before the property is put on the market.
- An honest and detailed presentation of the conservatory in the listing, supported by good photographs, allows you to make the most of it without creating false expectations.
Do not hesitate to seek professional support to calmly assess the role of your conservatory in your sale project and give your property every opportunity to be valued at the right price.
FAQ
What Is the Average Price of an Aluminium Conservatory?
The price of an aluminium conservatory generally falls within a mid-range to higher price bracket compared with PVC, due to the slimness of the profiles and the quality of the finishes available. The final cost depends heavily on the surface area, type of glazing and any solar protection options chosen.
Does a Conservatory Always Increase the Value of a House?
No, an increase in value is not automatic. It depends on construction quality, insulation, administrative compliance and local demand for this type of improvement. A poorly insulated or undeclared conservatory may instead make a sale more difficult or lead to downward price negotiations.
Do You Need Planning Permission for a 15 m² Conservatory?
In most cases, a 15 m² conservatory only requires a prior declaration of works, as it falls between the thresholds of 5 and 20 m². However, some municipalities lower this threshold in their local urban development plan, so it is essential to check the applicable rules with the local town hall before starting the project.
How Do I Know Whether My Conservatory Is Counted as Living Space?
A conservatory is counted as living space if it has sufficient thermal insulation for year-round use, a suitable heating system and a ceiling height that complies with current standards. If in doubt, a surveyor or real estate professional can check this before the property is put on the market.
What Are the Risks of Selling a House with an Undeclared Conservatory?
The notary may require the situation to be regularised before finalising the sale, which can delay or jeopardise the transaction. It is therefore preferable to check the administrative compliance of the conservatory as early as possible in the sale process and begin the regularisation process if necessary.
Is It Better to Build a Conservatory or Convert the Attic Before Selling?
This mainly depends on what the house genuinely lacks: a conservatory provides natural light and living space connected to the garden, while converting an attic before a sale often makes it possible to create one or more additional bedrooms. The most profitable choice is the one that most directly addresses an objective need perceived by potential buyers.
How Can I Estimate the Actual Impact of My Conservatory on the Selling Price of My Property?
The most reliable method is to compare your property with similar properties, with and without conservatories, recently sold in your area. A free online property valuation or a valuation carried out by a local advisor can provide an objective assessment, taking into account the construction quality of the conservatory and the specific expectations of the local market.
Can a Poorly Insulated Conservatory Reduce the Selling Price of a House?
Yes, this is possible if buyers perceive it as a source of future work, particularly if there is a risk of overheating in summer or heat loss in winter. In this case, it may be more appropriate to present the room as an additional space rather than as a genuine living room, in order to avoid disappointment during viewings.
Author :
Frédéric Rémy – Director of Commercial Performance
A real estate professional for several years within the Capifrance network, I would like to share with you some essential advice to help you succeed in your real estate project with the support of our advisors.
