A change of use from a commercial unit to a home can only be designed and signed by a qualified architect when the building's characteristic use is commercial or industrial. That is the binding doctrine set by Spain's Supreme Court in ruling 700/2026 of 4 June, which settles years of inconsistent criteria between town halls. The decision goes straight to the heart of a very common move on the Costa del Sol —buying a street-level commercial unit and turning it into housing— and it originates, as it happens, in a case from Alhaurín el Grande, in the province of Málaga.
What exactly has the Supreme Court decided?
The Administrative Chamber bases its decision on articles 2 and 10 of the Spanish Building Act (LOE), which allocate professional competences according to the nature of the works. The court concludes that moving from commercial to residential use belongs to the group of interventions reserved for architects, and elevates that reading to binding doctrine: it sets the criterion lower courts must follow and, in practice, the one municipal technical departments will apply.
The most revealing part is the argument it rejects. Technical architects had argued that requiring a full architect only made sense if the change affected the entire building or most of it, not a single unit. The Supreme Court dismisses that reading: what matters is not the size of the works but their nature. Turning a commercial space into a dwelling alters the architectural configuration of the property and affects habitability, safety and functionality, so it cannot be treated as a minor refurbishment even if only forty square metres are involved.
Why does the ruling originate in a town in Málaga?
The dispute began in Alhaurín el Grande. In 2018 a technical architect signed a change-of-use project and the town hall demanded that a full architect sign it instead. The professional body appealed, the case worked its way up through the administrative courts and has ended, eight years later, setting doctrine for the whole of Spain. For anyone buying in the province of Málaga there is a reassuring reading: the criterion the Supreme Court now endorses is the one many local technical departments were already applying.
Does it affect every change of use or only some?
The ruling needs to be read carefully, because it does not say that every change of use requires an architect. Andalusia's council of technical architecture bodies has clarified that the decision is confined to converting a commercial unit into a home inside a building whose characteristic use is commercial or industrial, and that it cannot be extended to every other scenario. Alfredo Sanz, head of Madrid's technical architects' association, sums it up by saying it is a very specific situation that cannot be applied automatically.
According to those same professional bodies, technical architects retain their competences in the following cases:
- Units located in buildings whose characteristic use is already residential.
- Refurbishment and renovation works that do not require an architectural project.
- Partial interventions on existing buildings.
- Site execution management, energy retrofits and conservation or maintenance works.
The practical takeaway is simple: before commissioning anything, check the characteristic use of the building the unit sits in. A ground-floor retail unit in a residential block in Fuengirola is not the same scenario as a warehouse or an entirely commercial building. And since the town hall applies the final criterion, a written preliminary consultation can save months of processing.
What do you need to convert a commercial unit into a home on the Costa del Sol?
Beyond who signs the paperwork, the route to converting a commercial unit into a home in municipalities such as Málaga, Marbella or Estepona is always the same, and the first step is the one that kills most deals.
- Check planning viability: the municipal general plan must allow residential use on that plot and on that floor. If it does not, no project will fix it.
- Verify the habitability requirements: minimum usable floor area, ceiling height, natural light and ventilation, accessibility and compliance with the Spanish Technical Building Code.
- Commission the technical project from the competent professional and have it certified by the relevant professional body.
- Apply to the town hall for the works and change-of-use licence, and pay the corresponding fees.
- Carry out the works and obtain the final completion certificate, the occupancy licence and the energy performance certificate.
- Update the Cadastre and the Land Registry so the property is recorded as a dwelling.
- Review the building's community statutes: if they expressly prohibit using commercial units as housing, the owners' association can object.
How much does a commercial-to-residential change of use cost?
There is no single figure, because each town hall has its own fee schedule and every unit starts from a different condition. These are the reference points used in the province of Málaga to get a sense of the order of magnitude.
| Item | Indicative reference |
|---|---|
| Who signs the project | An architect, if the building is commercial or industrial |
| Licence fee with no building works (Málaga city) | From €120 |
| Licence fee with building works (Málaga city) | Around €7.50 per built m² |
| Cost of the conversion works | Between €500 and €1,200 per m² |
| Usual minimum ceiling height | 2.50 m |
| Minimum usable area (studio, Málaga city) | 30.5 m² |
| Processing time | Varies by town hall |
On top of those items come the fees of the architect and the rest of the technical team, professional certification and, if the works are substantial, the construction tax. The rule of thumb is to set aside a buffer of 15% or 20% over the initial budget: older units almost always spring surprises in wiring, plumbing, damp or structure.
Is buying a commercial unit to convert into a home still profitable?
The move makes sense when the price of the unit plus the full cost of the conversion sits clearly below the market price of an equivalent home on the same street. That is where you need the real price per square metre for the municipality: in our monthly Costa del Sol market report, the median ranges from a little over €4,100 per square metre in Mijas to close to €5,900 in Marbella. With conversion costs of €500 to €1,200 per square metre the margin is real, but it is entirely wiped out by units without clear planning viability, without enough ceiling height, or without a façade where new openings can be made.
That is why the correct order never changes: planning first, numbers second. A cheap commercial unit that cannot legally become a home is not an opportunity, it is just a cheap commercial unit.
In summary
The Supreme Court has brought order to a question that depended for years on each town hall's judgement: if the building is commercial or industrial, the change-of-use project is signed by an architect. For buyers the reading is reassuring, because a properly signed project is one that will not collapse at the Land Registry or on a future resale, but it does mean doing your homework before buying the unit. At EVS PROPERTY GROUP we assess the viability of these operations in Málaga and across the Costa del Sol before you put money on the table: if you have a unit in your sights, tell us about it and we will look at it with you.
Frequently asked questions
Can a technical architect sign a commercial-to-residential change of use?
It depends on the building. If its characteristic use is commercial or industrial, ruling 700/2026 reserves the project for a qualified architect. In buildings whose characteristic use is already residential, the professional bodies maintain that technical architects keep their competences.
Does the ruling cancel licences already granted?
Not on its own. It sets doctrine for applications resolved from now on. If you have a project in progress signed by a different professional, the sensible step is to raise it with the town hall before a decision is issued.
What minimum area must a home have after the change of use?
It depends on municipal rules. Málaga city requires a minimum usable area of 30.5 square metres for a studio, with a usual minimum ceiling height of 2.50 metres. Each Costa del Sol town hall sets its own thresholds.
How long does a change-of-use application take?
This is the most variable part of the process: it depends on the workload of the planning department and on whether the works are classed as major building works. In the busiest coastal municipalities you should allow several months just for the licence.
Can the owners' association object?
Only if the statutes expressly prohibit using commercial units as housing, or if the works affect common elements, such as opening new windows in the façade. Checking the statutes before buying matters as much as checking the planning rules.
