Buying building land without the traps

Buildable land isn't a blank cheque. The local plan (PLU) or the communal map set what can be built, where, how, what height and what footprint. Two neighbouring plots can authorise two completely different projects.

Before anything, ask the seller for the exact PLU zone (U, AU, A, N) and the zone regulation. These documents are public, available at the town hall or on Géoportail. Without them, you don't really know what you're buying.

A U-zone plot is buildable immediately. AU is conditional, A is agricultural, N is natural. AU zones can stay frozen for years if the town hall doesn't open urbanisation. Treat with care.

The PLU looks unreadable. Focus on what really matters to a buyer. The maximum footprint coverage, the maximum height, density coefficient, setbacks from boundaries and street, aspect rules (roof, colours, materials), parking and green-space obligations.

A 30 % footprint on a 600 m² plot caps your house at 180 m² on the ground, sometimes less. A 7 m height at gutter rules out a comfortable two-storey. A 5 m setback on a narrow plot can make it almost unbuildable.

Get those numbers at the town hall. Cross-check with the project you have in mind. If the gap is wide, either adapt the project or change plot.

The operational planning certificate (CUb) is the simplest and cheapest way to secure a land purchase. You request it at the town hall, it's free, delivered within two months. It tells you officially whether your project is feasible, under what conditions and with what known easements.

Ideally request it before the compromis. Failing that, add a suspensive clause making the sale conditional on obtaining a favourable certificate.

A negative certificate kills the project. A positive one freezes the applicable planning rules for 18 months. Valuable protection if the town hall rewrites its PLU in the meantime.

A serviced plot is connected to water, electricity, sewage (collective or individual), phone and sometimes gas. An unserviced one can add €8,000 to €40,000, way more if networks are far.

Ask the town hall or utility operators for a working quote. Budget €1,500 to €3,000 for electricity if the grid is at the boundary, tens of thousands if you need to pull 200 metres of cable.

For sewage, if the commune has no mains drain, you need a septic tank + drainage field signed off by the SPANC. Budget €8,000 to €15,000 depending on soil.

Under French ELAN law, a G1 soil survey is mandatory at sale on land exposed to clay shrinkage. It assesses geotechnical constraints and dictates the type of foundations needed.

A G2 (pre-project) study sizes foundations precisely against the project. It costs €1,500 to €3,000 but can reveal the need for piles or beams that add €15,000 to €40,000 to construction.

Without a serious study, you risk cracks at the first drought, expensive remedial work, and an insurance claim that may be denied. A G2 before signing is real protection.

Land can carry easements (right of way, right of view, pipes, power lines). They're published at the land registry and picked up by the notary. Always ask for the cadastral extract and the mortgage record.

Check party walls, hedges, fences. A party wall makes you liable for 50 % of upkeep. A disputed hedge is a daily nightmare.

Pop into the town hall: upcoming developments, pending permit applications, aircraft or rail noise zones. All public, all decisive for perceived value.

Géorisques (French risk portal) lists risks at the address for free: flood, clay shrinkage, seismic, radon, ground movement, classified industrial sites. A Red flood zone is unbuildable. A Blue zone may be buildable under heavy technical conditions.

High clay risk forces reinforced foundations and a mandatory G2 study. High radon weighs on design (forced ventilation). Proximity to a SEVESO site must appear in the risk statement annexed to the compromis.

None of these kill a project, but they add cost and constraints worth knowing before signing.

Land price depends on the commune, the surface, but above all the real build rights. An 800 m² plot at 30 % coverage is worth more than 1,200 m² at 15 %. What counts is buildable area, not gross size.

Look at recent comparable sales in Etalab's DVF database. Adjust for utilities, easements, PLU and soil quality. You'll land on a realistic range.

On an unserviced plot, deduct the estimated utilities cost from the price. Sellers expect this negotiation, don't let it slide.