What to check in a property with existing buildings

The fact that a building has stood for years, appears in the listing photos and is used normally does not necessarily mean it is in order from a planning standpoint. On rural properties it is relatively common to find buildings that were originally built without a permit, that were extended beyond what was originally authorised, or that are put to a use different from the one they were permitted for, and that situation may not be obvious at a glance during a viewing.

This is an important difference compared with buying a home in an urban setting, where the existence of the building is almost always accompanied by a clear administrative status from the outset. On rustic land, construction and its administrative regularisation have not always gone hand in hand, particularly for old buildings put up at a time when there was less planning control than exists today, or for buildings that were gradually extended over the years without each extension being properly processed. This pattern of gradual, poorly documented growth is precisely what makes it so important to check each building on its own merits, rather than trusting the overall impression the property gives.

This guide explains what to check when a property includes a building (a house, a barn, a warehouse, any other structure) before buying it, and what risks are involved in acquiring a property with buildings whose legal status is unclear. It complements the guide on what documentation to request before buying a property and the guide on the planning status of the land, focusing specifically on what is already built.

This check is especially relevant for the types of property where the building carries significant weight in the total value of the property, such as manor farmhouses, granges or any property intended for residential use; on purely undeveloped land, this guide loses practical relevance, though it is still worth bearing in mind should a small shed or outbuilding that seemed irrelevant at first glance turn up at some point.

The reference document is the building permit (or the equivalent authorising title under each municipality's regulations) that authorised the construction at the time, together with the completion certificate confirming the building was carried out as authorised. If the building has had later renovations or extensions, each one of them should have its own permit or authorisation, not just the original construction, since a valid initial permit does not automatically cover extensions made later without processing their own authorisation.

The cadastral certificate, besides stating the built area, usually includes the declared year of construction; comparing this date with that of the available permit, if any, helps detect possible inconsistencies. It is also worth checking whether the building is reflected in the title deed and in the land registry extract, since a building not registered may indicate that its status was never properly formalised after construction, even if it has existed for tax and cadastral purposes for some time.

If there is no permit because the building is very old, there may be a route to some form of recognition of an existing situation (a declaration of assimilation to a legal-nonconforming status or similar, depending on how each region names it), which does not amount to a permit but can partially regularise the situation under certain conditions. Confirming whether this route applies, and exactly what it involves, requires consulting the town council or a specialised professional, since the conditions vary by local regulations.

It is worth being clear that this figure, where it exists and applies, does not turn the building into legal in the same sense as a permit: it normally acknowledges that, given its age, demolition can no longer be required, but it can still carry limitations on renovating it, extending it or changing its use in future. Understanding this difference avoids forming too optimistic an idea of what this type of administrative recognition really provides, since in practice it tends to function more as limited tolerance than as full regularisation.

Some signs are worth investigating more closely: buildings that, at a glance, look bigger or more recent than what appears in the cadastral certificate; barns or warehouses that have, over time, been turned into homes without that change of use being recorded; or visible extensions (an added floor, a built annexe) that do not match the available documentation. Comparing old photographs of the property, if available, with its current state can also help identify changes that have not been formally declared.

It is also worth paying attention to the state of the installations (electricity, water, drainage): highly elaborate installations in a building registered as agricultural or ancillary can indicate an undeclared de facto residential use, which may have both planning and tax implications worth clarifying before buying. A heating system, a full bathroom or an equipped kitchen in a warehouse registered as storage are details that, though they may seem minor, tend to point to a use different from the one officially declared.

None of these signs on its own confirms a problem, but all of them justify asking directly and requesting the corresponding documentation before going any further. The seller may not be aware of any irregularity if the building was put up a long time ago or by a previous owner, so it is worth approaching these questions without assuming bad faith, but with the same seriousness as the rest of the checks.

It is also worth asking whether an attempt was ever made to legalise or regularise any of the buildings, and what the outcome of that process was: a failed legalisation attempt is usually a clearer sign that there is an underlying problem worth understanding well before buying, rather than assuming no one ever tried. If the attempt failed for a specific, known reason, that information is far more valuable than starting your own investigation from scratch.

Buying a property with an undeclared or unlicensed building does not always prevent the purchase, but it does transfer to the buyer a series of risks worth understanding before deciding: the impossibility of obtaining mortgage financing secured on that particular building, difficulties insuring it adequately, limitations on renovating or extending it in future, and, in some cases, the possibility that the authorities may at some point demand legalisation or, in the worst-case scenario, demolition of what was built without authorisation. None of these risks disappears simply because the purchase was made in good faith; they pass along with the property, unless resolved before signing.

These risks are not the same in every case: an old, well-established building with no complaints or open enforcement proceedings usually carries a different risk from a recent, clearly irregular one. Assessing this difference with the help of a professional (an architect, a lawyer specialising in planning law) allows for a more informed decision as to whether the risk is acceptable for the specific project or whether the deal should be reconsidered, rather than treating any detected irregularity as an automatic reason to rule out the property without further analysis.

If you decide to go ahead despite a detected irregularity, it is worth reflecting this explicitly in the negotiation: adjusting the price accordingly, recording the known situation in writing in the contract, and planning from the start whether an attempt will be made to regularise the building after the purchase and at what estimated cost, rather than simply accepting the situation and discovering its consequences later.

It is also worth weighing the reputational risk and peace of mind involved in living or working in a building whose status is unresolved: beyond the specific economic or legal implications, for many buyers the uncertainty of not knowing whether the authorities might at some point act on the building is, in itself, a cost worth weighing when deciding whether the deal is worthwhile, even if the objective risk of that actually happening is, in practice, relatively low in many specific cases.

The first step is to ask the seller for all available documentation on the buildings (permits, completion certificate, any existing technical project) and compare it with what is observed during the viewing and with the cadastral certificate. If the documentation provided is incomplete or non-existent, it is worth requesting directly from the town council information on the plot's planning history, including whether there is any open enforcement or disciplinary file, since this type of file may not be visible from outside nor mentioned spontaneously by the seller.

Commissioning an independent technical inspection, carried out by an architect or building surveyor, is a particularly advisable option when the building's value represents a significant part of the property's total price, or when the project depends on being able to use, renovate or extend that building in future. The cost of this inspection is usually modest compared with the risk of discovering a serious problem after buying.

It is worth planning this check well in advance of the expected signing date, since gathering all the municipal documentation and, where applicable, commissioning a technical inspection can take several weeks. Leaving this review until the end of the process, when there is already pressure to close the deal, tends to lead to accepting more risk than would have been accepted with a clearer head.

Once the review is complete, it is worth sharing the findings with the seller clearly and directly, rather than keeping doubts to yourself for later or trying to use them only as a negotiating tool at the last minute. A transparent conversation about what has been found usually makes it easier to reach an agreement fair to both parties, whether by adjusting the price, clarifying the situation or, if the problem is serious, deciding not to proceed with the deal.

Not all buildings on a property receive the same planning treatment or carry the same level of risk. A tool shed, a small agricultural storehouse or a fenced enclosure are usually subject to different requirements (and, generally, less strict ones) than a home or a building of a certain size, precisely because their use and impact are different. It is worth not treating all the buildings on a property as a single homogeneous block when assessing their legality, since grouping very different checks under one superficial review can cause relevant nuances of each one to be overlooked.

This matters because, in practice, it is common for a property to combine buildings with different degrees of regularisation: for example, a home with a clear permit alongside a warehouse extended without authorisation years later. Reviewing each building separately, rather than assuming the whole property shares the same legal status, gives a much more accurate picture of where the risk actually lies, and allows the price to be negotiated in proportion to the specific problem detected, rather than applying a generic discount to the property as a whole.

If the purchase project includes an intention to build new ancillary structures in future (a warehouse, a shed, a fence), it is worth using the initial planning enquiry to also confirm what type of ancillary buildings are permitted and under what conditions, rather than assuming this type of minor construction requires no procedure at all.

As a general reminder, it is worth keeping in mind that the absence of a procedure does not mean the absence of regulation: even small, seemingly insignificant buildings may be subject to some form of notification or authorisation depending on the municipality, and checking this in advance avoids starting work with good intentions but without the proper administrative cover, which in the long run can generate exactly the same type of problem one is trying to avoid by checking the legality of the buildings that already exist.