If you own a property in Spain and are planning any kind of building work, one of the first questions your builder or architect will ask is whether the job counts as an obra menor or an obra mayor. It sounds like bureaucratic detail, but the answer decides how long you wait for permission, how much you pay the town hall, whether you legally need an architect, and — crucially — how much personal risk you carry if anything is done without the right paperwork.
British owners are often surprised to learn that in Spain the property owner, not the builder, is the person the town hall holds responsible for an unlicensed job. A cowboy builder who tells you "don't worry, we don't need a permit for that" is not the one who receives the fine or the demolition order. You are. This guide explains the difference in plain English, with the timelines and costs you should expect in 2026.
The three permit categories, not two
Most people talk about obra menor versus obra mayor, but Spanish municipalities actually run three regimes, and knowing which one applies saves you both time and money.
- Obra mayor — major works. Anything affecting the structure, the footprint, the facade, the roof, or the use of the building. New builds, extensions, swimming pools, removing load-bearing walls, and full property reforms fall here. Requires a project drawn up and signed by an architect (arquitecto) and, often, a technical architect (aparejador) to supervise.
- Obra menor — minor works. Non-structural jobs that change layout or installations without touching the bones of the building: a new kitchen or bathroom, replacing plumbing or wiring, re-tiling, internal non-load-bearing partitions. No architect's project needed in most cases.
- Declaración responsable — a responsible declaration. For light, purely cosmetic work — painting, replacing floor tiles like-for-like, changing kitchen units without moving services. You declare the work and can usually start almost immediately, with the town hall checking afterwards.
The grey area is real: whether knocking through two rooms is "menor" or "mayor" depends on whether the wall is load-bearing, and different town halls draw the line differently. When in doubt, ask the ayuntamiento or a local architect before work starts, not after.
How long each one takes
Timelines vary enormously by municipality — a small inland town may be quicker than a busy coastal one — but as a realistic 2026 guide:
- Declaración responsable: effectively immediate. You submit, pay, and can generally begin, subject to later inspection.
- Obra menor: roughly 15 to 45 days for approval.
- Obra mayor: anywhere from 1 to 6 months, and on the higher end for coastal or protected areas where additional reports (coastal authority, heritage, environmental) are required.
Build these waits into your planning. A common and expensive mistake is booking a builder and materials for a spring start, then discovering the obra mayor licence for a pool or extension will not land until summer.
What it costs: ICIO, licence fees and the architect
There are three separate costs to a Spanish building permit, and they are often confused.
1. ICIO — the construction tax
The Impuesto sobre Construcciones, Instalaciones y Obras is a municipal tax charged as a percentage of the Presupuesto de Ejecución Material (PEM) — the official estimate of materials and labour, excluding VAT and professional fees. By law the ICIO cannot exceed 4%, and most town halls set it between 2% and 4%. For reference, Madrid charges around 3.75%, Barcelona roughly 3.35%, and Valencia up to 4%; many medium-sized towns sit around 2.5–3%. Always check your own municipality's rate.
2. The licence fee (tasa)
Separate from the tax, the town hall charges an administrative fee. For an obra menor this is often a modest fixed amount — commonly in the €50–€300 range — while for an obra mayor it is typically a further 1–2% of the PEM.
3. Professional fees
An obra mayor needs an architect's project and usually site supervision, which adds architect and aparejador fees on top. An obra menor usually does not, which is a large part of why the two categories differ so much in total cost.
A useful money-saving note: many municipalities now offer ICIO reductions of 50–95% for work that delivers certified energy improvements. If your reform includes insulation, efficient glazing or a heat pump, ask whether a bonificación applies before you file — it can materially cut the bill. Our full guide to the licencia de obra goes into the paperwork in more detail.
A worked example: kitchen reform vs a new pool
Imagine two British owners on the Costa Blanca, both near Alicante.
Owner A is refitting a kitchen — new units, re-tiling, moving the sink and re-running plumbing, no walls touched. This is an obra menor. On a PEM of, say, €18,000, the ICIO at ~3% is about €540, plus a fixed licence fee of perhaps €150. No architect required. Total permit cost: under €700, with approval likely inside a month.
Owner B is adding a swimming pool and a covered terrace. This alters the plot and requires structural and drainage work, so it is an obra mayor. On a PEM of €40,000, the ICIO at ~3% is about €1,200, the licence fee at ~1.5% adds roughly €600, and an architect's project plus supervision might be €2,500–€4,000. Total permit-and-professional cost: comfortably €4,000+, with approval potentially taking three to six months.
Same coastline, same year — but the category, the timeline and the bill are worlds apart. Knowing which one you are in before you sign a builder's quote is what keeps a project on budget.
What happens if you skip the permit
Skipping the licence is not a victimless shortcut. The risks fall on the owner and include:
- Fines. Town halls can levy penalties that often dwarf what the licence would have cost.
- Legalisation orders. You may be required to apply for the licence retrospectively (paying extra), or in the worst case to undo the work.
- Problems when you sell. Unlicensed extensions and pools that do not match the Land Registry (Registro de la Propiedad) or cadastre routinely derail sales, spook buyers' lawyers, and knock money off the price.
Because the paperwork travels with the property, an unlicensed job you inherit — or leave behind — becomes the next owner's problem too. It is one of the most common reasons a Spanish sale falls through late in the process.
How to protect yourself
The practical checklist for any British owner is short: confirm the category with the town hall or an architect before work starts; insist your builder's quote states which licence applies and includes the permit; keep copies of the licence and receipts; and never accept "we don't need one for this" without checking yourself, because you are the one who carries the liability.
Good builders handle this as standard — they tell you which permit is needed, factor the timeline into the schedule, and won't start an obra mayor without the licence in hand. If you'd rather not navigate the ayuntamiento alone, post your project on BuildSpain and we'll match you with up to three vetted, English-speaking builders in your region who understand the permit process. It's free and there's no obligation — a simple way to start with builders who do the paperwork properly.