property types

What is an underbuild in Spanish property?

An underbuild (commonly called sótano or planta baja) is a lower level built into the slope of a hillside property, situated beneath the main living area.

It's a very common feature in Costa Blanca villas, particularly in hillside urbanizations.

Underbuilds can provide significant additional space — often 50-100+ square meters — used as garages, storage, extra bedrooms, games rooms, home gyms, workshops, or even separate apartments.

Key considerations: check if the underbuild is legally registered (declared) in the escritura and matches the catastral records.

Many underbuilds were built without proper permits and may not be counted in the official square footage.

Undeclared underbuilds can affect property value, insurance, and future sale.

Converting underbuilds to habitable space may require permits and must meet building regulations for ventilation, ceiling height, and emergency exits.

Properly declared and converted underbuilds significantly increase property value and versatility.

WOW-Estates verifies underbuild status during due diligence.