Estate agents in Spain like the phrase "excellent road access". A plot with a long frontage on a national road (carretera nacional) looks easy to reach, easy to connect to services and easy to sell on. What the listing rarely says is that Spanish road law forbids building in a strip next to the road, 25 metres deep beside an ordinary state road and 50 metres beside a motorway, and that any works in a much wider band need the road authority's permission on top of the town hall's building licence.
A notice in Spain's official gazette, the BOE, of 30 April 2016 shows what that means on the ground. The State Roads Office for Western Andalusia (Demarcación de Carreteras del Estado en Andalucía Occidental) put out for public consultation a study covering "Las Monjas", a cluster of houses in Carmona, near Seville, along the left side of the A-4 motorway between kilometre points 516+512 and 516+999. Houses had gone up there over the years inside the strip where nothing may be built. The Ministry proposed to declare the stretch an urban section and move the building line. The notice was blunt about the houses that would still sit in front of the new line: they would be "out of planning compliance" (fuera de ordenación), only conservation and maintenance works could be authorised, and anything demolished would have to be rebuilt behind the line. At the junction serving the estate, the line stayed at 50 metres.
Ten years on, the same procedure is still how the line moves, one short stretch at a time. In October 2026 alone the BOE carried final approval of a new line on 150 metres of the N-634 in Valdés (Asturias), a new urban section on the A-64 in Siero, and a public consultation on the N-320 run by the Castilla-La Mancha roads office. Everywhere else, the default distances apply.
This guide is for buyers, often abroad, looking at a plot or a house beside a road. It covers the state rules, how three regions differ, the arithmetic of what you lose, what to check yourself before paying a deposit, and what to do if the answer is bad. It is a screening guide, not legal advice on a particular property.
Key terms
| Spanish term | What it means for you |
|---|---|
| Red de Carreteras del Estado | state road network (A-, AP- and N- roads, mostly), run by the Ministry of Transport |
| Demarcación de Carreteras | the Ministry's regional roads office that issues permits |
| calzada | the carriageway: the paved lanes, not the hard shoulder |
| explanación | the whole road works: carriageway, shoulders, ditches and embankments |
| arista exterior | outer edge (of the carriageway or of the road works) from which distances are measured |
| dominio público | land that belongs to the road |
| zona de servidumbre | easement strip: still your land, but heavily restricted |
| zona de afección | "affected zone": any works need the road authority's prior permission |
| línea límite de edificación | building line: nothing may be built between it and the road |
| zona de limitación a la edificabilidad | the strip between the road and the building line |
| tramo urbano / travesía | urban section / stretch through a village, where different rules apply |
| fuera de ordenación | an existing building that no longer complies: it can be kept and maintained, not enlarged |
| p. k. (punto kilométrico) | kilometre point, the address of any spot on a Spanish road |
| arras | the private deposit contract usually signed before the notary deed |
Whose road is it?
The distance depends on who owns the road, and Spain has three layers:
- State roads, governed by Ley 37/2015, de 29 de septiembre, de carreteras, and run by the Ministry of Transport and Sustainable Mobility through its regional Demarcaciones.
- Regional roads, under each region's own road act: Andalusia's Ley 8/2001, Valencia's Ley 6/1991, Galicia's Lei 8/2013, Catalonia's Decreto Legislativo 2/2009.
- Provincial roads, run by the diputación (provincial council) or, on the islands, the cabildo or consell, under regional law.
Do not judge by the road number alone. In Andalusia the A-4 is a state motorway, while the A-392 and A-376 are regional roads of the Junta de Andalucía. Same letter, different owner, different statute, different office that grants permits.
The state rules in one table
Ley 37/2015 sets four protection zones on each side of a state road (article 28). Three are measured from the outer edge of the road works (explanación); the building line is measured from the outer edge of the carriageway (calzada).
| Zone | Motorways and dual carriageways (autopistas, autovías) | Ordinary and multi-lane roads | Measured from | Article |
|---|---|---|---|---|
| Road land (dominio público) | 8 m | 3 m | edge of road works | 29 |
| Easement (servidumbre) | 25 m | 8 m | edge of road works | 31 |
| Affected zone (afección) | 100 m | 50 m | edge of road works | 32 |
| Building line | 50 m | 25 m | edge of carriageway | 33.1 |
| Building line at junctions, slip roads and turning lanes | 50 m | 50 m | edge of carriageway of each ramp | 33.2 |
Two consequences that surprise foreign buyers:
- The building line does not start at your fence. It is measured from the edge of the tarmac lanes. If the road sits on a wide embankment, the law makes the line coincide with the outer edge of the easement strip instead, so you cannot gain land by arguing about the slope.
- Being behind the line is not the end of it. A house 35 metres from an ordinary national road is outside the no-build strip but still inside the 50-metre affected zone. Before building there, ask the roads office for a permit as well as the town hall licence; the same goes for a fence, a pool, a well or a shed in that band.
The regulation changed in October 2025
Many English-language guides, and plenty of Spanish ones, still quote the 1994 General Roads Regulation (Real Decreto 1812/1994). It was replaced by Real Decreto 899/2025, de 9 de octubre, a new Reglamento General de Carreteras published on 10 October 2025 and in force since 30 October 2025. The old regulation is repealed except for one paragraph of a transitional provision dealing with property rights in the widened no-build strip. Article 96 of the new regulation deals with the no-build strip, and a transitional provision covers applications already lodged before 30 October 2025.
Who gives permission, and how
For a state road outside an urban section, permission comes from the Ministry through the Demarcación de Carreteras or its provincial unit. It is separate from the town hall's building licence (licencia de obra): the roads permit is granted subject to any other licences and without prejudice to third parties, and the town hall licence does not replace it. You, or your architect, will run two files in parallel.
An application typically carries the owner's details, the cadastral reference (referencia catastral), a location plan with the road, kilometre point and side, a dimensioned site plan showing distances to the edge of the carriageway and of the road works, and a description of the works. Do not rely on silence: wait for a written decision before you start.
On deadlines, be careful with what you read online: regional roads have their own rules, and for state roads do not plan a build on the assumption that no answer means yes.
Through villages the rules shift. Where the Ministry has declared an urban section (tramo urbano, article 48), the split of powers between the Ministry and the town hall changes; ask both who grants your permit.
How the line gets moved
There are two legal routes to bring the line closer than 25 or 50 metres:
- An urban-section study under article 48, as at Las Monjas and, in 2026, in Valdés and Siero. The roads directorate approves a draft, the BOE publishes it, there is a consultation period (30 working days in the notices reviewed), and the Minister approves it. The new line follows the town planning in force when Ley 37/2015 came into effect, so a later local plan does not move it by itself.
- A reduction under article 33.3 for geographic or socio-economic reasons, without declaring an urban section. The BOE of 27 March 2025 carries one for the N-352 in Ceuta.
Read the exact limits. The Valdés approval, signed on 2 October 2026 and published on 13 October, covers only the left side of the N-634 between kilometre points 504+490 and 504+640. The Siero one covers the left side of the A-64 from 29+630 to 30+000. A house on the opposite side, or a few metres past the end point, keeps the default line.
Regional roads: three examples
Andalusia (Ley 8/2001). Uses a "no-build zone" (zona de no edificación, article 56), measured from the outer edges of the carriageway in the wording given by Decreto-ley 26/2021. In practice, a 2006 regional gazette notice set the line at 50 metres on the A-392 and 25 metres on the A-376. The Junta can widen or narrow the zone on specific stretches after hearing the town hall, and inside urban stretches the local plan's alignments decide.
Galicia (Lei 8/2013). After Lei 3/2018, article 41.1 sets the building line at 50 metres on motorways and similar roads and 15 metres on conventional roads; where the road owner has approved its network catalogue, 15 metres on structural and complementary roads and 7 metres on local roads. A 2023 decree refers to a change in the reference point towards the edge of the road works.
Valencia (Ley 6/1991). Still in force, amended several times. Article 33 sets a protection zone; in urban and development land the local plan can fix its width with a favourable report (art. 33.2), and otherwise the law sets default distances, including 25 metres for roads outside the main network (art. 33.3, as quoted by the competition authority CNMC).
On a provincial road, ask the diputación: it grants the permits for its own network.
The arithmetic: one plot, three roads
Take a plot 25 metres wide and 50 metres deep (1,250 m²), frontage along the road. Assume the town plan requires a 5-metre setback at the back and 3 metres on each side; your real figures are in the local planning rules (normas urbanísticas).
Beside a state motorway. Say the carriageway edge to the outer foot of the embankment is 12 metres, and road land runs 8 metres further, so your boundary is 20 metres from the carriageway. The building line is at 50 metres, i.e. 30 metres into your plot.
- No-build strip: 25 × 30 = 750 m², 60% of the plot.
- Depth left: 50 − 30 − 5 = 15 m. Width left: 25 − 3 − 3 = 19 m.
- Footprint envelope: 19 × 15 = 285 m².
- The whole plot is inside the 100-metre affected zone, so every project needs the Ministry's permit.
Beside an ordinary national road (N-). Shoulder plus ditch 3 metres, road land 3 more: boundary 6 metres from the carriageway. Building line at 25 metres, 19 metres into the plot.
- No-build strip: 25 × 19 = 475 m², 38%.
- Envelope: 19 × (50 − 19 − 5) = 19 × 26 = 494 m².
- Affected zone to 53 metres from the carriageway; the plot runs from 6 to 56 metres, so all but its last 3 metres need the Ministry's permit for any works.
Beside a catalogued local road in Galicia, with a 7-metre line and the boundary at, say, 4 metres from the carriageway: 3 metres lost at the front, an envelope of 19 × 42 = 798 m².
Same plot, same asking price, between 285 and 798 m² where a house can go. If the listing price is per square metre, recompute it per buildable square metre. Whether the plan's floor-area ratio is applied to the whole plot or only to the buildable part is set in the local planning rules; ask the town hall's planning department, because it changes the size of house you can build.
On rustic land (suelo rústico) the road setback comes on top of the region's minimum plot and other conditions; it does not replace them.
The TerrenoCheck report for a plot (€29 in one language, €39 in two) puts the cadastral parcel on a dated orthophoto next to the road, with land classification, planning, flood zones and protected areas, each with its source. It does not set the legal building line: the roads office does. Mark your plot on the map → · See a sample report
What the agent will not tell you
- "Room for an extension." If the house sits inside the building line it is fuera de ordenación: maintenance yes, extra volume no. Adding volume without a permit is an infringement under article 41 of Ley 37/2015.
- "The town hall gave the licence." A municipal licence does not cover the roads permit. Ask for both.
- "The pool and the garage are legal." Built in the affected zone without the roads permit, they are not, whatever the cadastre shows. The roads administration can fine and order the land restored.
- "They are about to change the line." Maybe. Ask for the BOE notice and check that your side and kilometre points are inside the stretch.
- "Rebuild and you can have a bigger house." A demolished building must be rebuilt behind the line, which on a shallow plot can mean nowhere.
Buying from abroad: what to sort out and when
You will need a foreigner's identification number, the NIE, to complete the purchase; our NIE guide covers it. If you cannot be in Spain, a lawyer or trusted person can sign under a power of attorney (poder notarial), granted before a Spanish consul, or before a notary at home with the formalities your Spanish notary asks for (usually apostille and sworn translation). Make sure the power allows them to request planning documents and lodge applications, not only to sign the purchase.
The timing matters more than the paperwork. The Spanish sequence is usually a reservation, then a private deposit contract (contrato de arras), then the notary deed. Depending on the type of arras, walking away can cost you the deposit (see our arras guide). So the road questions belong before the arras:
- Road number, owner and kilometre point.
- Distance from the edge of the carriageway to where you want to build, measured on a plan, not paced along the verge.
- Any BOE or regional-gazette notice on a building line for that stretch.
- A planning certificate from the town hall (see planning certificate) that mentions road constraints.
- For an existing house: year built (in the cadastre), licence and roads permit.
- A written query to the Demarcación with location plan and cadastral reference if the margin is tight.
If you cannot get answers in time, write a condition into the arras: the deposit is refundable if the roads office or the town hall confirms that the planned house cannot be built in a stated position. Your lawyer will word it; you need to know to ask.
If the answer is bad
- The line takes half the plot. Redo the envelope with the plan's setbacks. If your house no longer fits, the price per usable square metre has doubled. Negotiate on that number or walk away before the arras.
- The existing house is in front of the line. Price it as a house you can keep and repair, not enlarge. Have the seller state in the deed which licences and permits exist, and ask a local architect whether your planned works count as maintenance.
- Outbuildings were put up without a roads permit. Make legalisation, removal or a price cut a condition of sale, and keep responsibility with the seller in writing. A sanction reaches the current owner.
- The stretch is under study. Read the notice and its plan, check your side and kilometre points, and file comments within the consultation period if you already own. If you do not, do not pay today for a line that may move later.
- You have already bought and the plot is unbuildable. See a Spanish planning lawyer about the article 33.3 or urban-section routes, and about whether the sale misled you. The law allows claims by owners who prove their rights were impaired by the no-build strip, on strict conditions.
Before you write to a roads office or a lawyer, have the plot's cadastral reference, classification and an up-to-date orthophoto at hand. They are on the first pages of the TerrenoCheck report, with sources and dates. Get the report for your plot → · See a sample report