DA DB-SI / 4 Building Exit and Safe Outdoor Space - Spanish Building Code Support
The DA DB-SI / 4 Salida de edificio y espacio exterior seguro is a technical support document issued by the Ministerio de Fomento through the Secretaría de Estado de Infraestructuras, Transporte y Vivienda and the Dirección General de Arquitectura, Vivienda y Suelo in Spain. Published on July 13, 2016, this document serves as a regulatory clarification for the Documento Básico DB-SI (Fire Safety) within the Código Técnico de la Edificación (CTE). It provides specific technical guidance on the application of definitions found in Anejo SI A, focusing on the requirements for building exits and the safe outdoor spaces where evacuation is considered complete.
The document is structured into six primary sections that detail the definitions, dimensional requirements, and situational exceptions for fire evacuation routes. It governs a wide range of building types and urban scenarios, providing formulas for occupant dispersion and criteria for heat and smoke dissipation. Key regulatory domains covered include the calculation of safe areas based on occupant load (P), the communication of these spaces with the public road network, and the specific conditions under which building roofs or interior courtyards may be designated as a espacio exterior seguro (safe outdoor space).
By outlining the interplay between building exits and safe arrival points, the document defines the point at which an evacuation process is legally concluded. It addresses practical challenges in dense urban environments, such as the use of patios de manzana (city block courtyards) and the necessity of legal easements for passage. The following sections detail the technical thresholds and verification methods required by the DB-SI framework to ensure occupant safety during fire events.
Definition of Building Exit and Safe Outdoor Space
A salida de edificio is defined as a door or opening that leads directly to a safe outdoor space. However, specific allowances are made for exits with limited occupant loads.
- Occupancy Limit: Exits intended for a maximum of 500 people may be valid if they lead to an outdoor space with two alternative paths to safe areas.
- Path Distance: At least one of the alternative paths must not exceed a distance of 50 m.
- Functional Integration: The document emphasizes that building exits and safe outdoor spaces are interdependent concepts defined in Anejo SI-A.
Conditions for a Safe Outdoor Space
To be classified as a espacio exterior seguro, a location must ensure that evacuation is fully terminated by meeting six specific conditions related to dispersion and access.
- Occupant Dispersion: The space must allow occupants to leave the building and disperse safely.
- Heat and Smoke Dissipation: The area must permit the wide dissipation of heat, smoke, and gases produced by a fire.
- Emergency Access: It must allow access for firefighters and aid personnel, though vehicle access is not always strictly required for spaces like interior patios.
- Building Distance: If the space does not communicate with a road network, a minimum distance of 15 m from any part of the building is required, unless the building is divided into independent fire sectors.
Dimensions and Surface Area Verification
The adequacy of a safe outdoor space is verified through numerical checks of the available surface area relative to the number of occupants (P).
- Surface Ratio: A minimum area of 0.5P m² must be available for dispersion.
- Search Radius: This area must be located within a radius of 0.1P m from the building exit.
- Threshold for Calculation: Numerical verification is required when the number of occupants (P) exceeds 50 people.
- Blocking Hypothesis: When two exits are required, the calculation must assume one is blocked to determine the necessary surface area of the remaining space.
Special Urban Scenarios and Building Roofs
The document provides guidance for complex urban configurations, such as courtyards and rooftop evacuations.
- Patios de Manzana: Evacuation through courtyards, hallways, or passages is acceptable if a servidumbre legal de paso (legal easement of way) is established.
- Independent Sectors: Buildings divided into structurally independent fire sectors may treat each sector as a separate building for evacuation calculations.
- Building Roofs: A roof may be a safe outdoor space if its structure is independent of the building being evacuated and fire resistance is sufficient.
- Ownership Requirements: For roofs belonging to other buildings, legal easements or unified property management (horizontal property) are required to prevent blocked exits.
Frequently Asked Questions
What is the minimum surface area required for a safe outdoor space?
The required surface area is at least 0.5P m², where P is the number of occupants expected to use the exit.
At what occupant count must the dispersion area be numerically verified?
Verification is mandatory when the occupant load (P) exceeds 50 people.
Can a building exit lead to an outdoor space that is not yet 'safe'?
Yes, if the exit serves fewer than 500 people and offers two alternative paths to safe areas, one of which is within 50 m.
What is the required distance from the building if the safe space lacks road access?
The safe zone must be at least 15 m away from any part of the building to account for limited dispersion.
Are firefighters required to have vehicle access to every safe outdoor space?
Not necessarily; access for personnel and aid equipment is required, but vehicle access may be omitted in cases like interior patios.
When can a roof be used as an evacuation end point?
A roof is valid if it has an independent structure, sufficient fire resistance, and, if belonging to another building, a legal easement of way.
How is the radius for the dispersion area calculated?
The radius for the dispersion zone is calculated as 0.1P meters from the building exit.
What happens if a building is divided into independent fire sectors?
Each sector can be considered a separate building, meaning surface area calculations for dispersion only need to account for that specific sector's occupancy.
