Annex 1b – Pre-accepted Fire Safety Solutions for Secondary Buildings
Annex 1b is an official technical supplement to the Danish Building Regulations 2018 (BR18), specifically supporting the guidance for Chapter 5 - Brand (Fire). Issued by Bolig- og Planstyrelsen (the Danish Authority for Social Services and Housing), this document outlines standardized, pre-accepted solutions for fire safety in secondary structures associated with detached and semi-detached single-family houses, including summer houses. Under BR18 § 5, secondary buildings up to 50 m² may be constructed or modified without a formal building permit application, provided they adhere to the technical requirements detailed in this framework.
The scope of this document covers one-story structures such as garages, carports, outbuildings, greenhouses, chicken coops, and covered terraces. These are categorized under Usage Category 1 (Anvendelseskategori 1) and Risk Class 1 (Risikoklasse 1). The guidance provides specific technical values for building placement, fire-resistant materials, and documentation requirements. It defines structural criteria for both open buildings (where at least half the facade area is open) and closed buildings, such as enclosed garages with automated or manual doors. Key regulatory areas include horizontal fire spread prevention, distance to boundaries, and rescue service access.
The following sections detail the specific technical thresholds for horizontal fire spread, distance requirements to primary buildings and property lines, and the mandatory documentation levels for different fire classes.
Classification and Technical Definitions
Secondary buildings governed by this annex must meet specific criteria regarding their use and fire load to be classified under risk class 1. These buildings are intended for short-term human occupancy and must not be used for sleeping accommodations.
- Usage Category 1: Occupants must be familiar with escape routes and capable of self-evacuation.
- Risk Class 1: Limited to 1 story above ground and 1 story below ground, with a fire load not exceeding 1,600 MJ/m² of floor area.
- Brandklasse 1: Covers total floor areas up to 600 m² per building section, utilizing simple fire protection installations and manual fire-extinguishing equipment.
- Open Buildings: Defined as structures where at least half the facade area is open, with no internal walls and a maximum distance of 8.0 m from any point to an open facade.
Distance Requirements and Fire Spread Prevention
The prevention of horizontal fire spread is primarily managed through minimum distances to property lines, roads, and primary buildings. These distances vary based on the type of roofing material and the presence of fire-rated walls.
- Boundary Distance (Table 4.4.1): Buildings with class BROOF(t2) roofing generally require a 2.5 m distance to property lines, though certain open structures may be placed 1.0 m from the boundary.
- Distance to Primary Buildings (Table 4.4.2): Secondary buildings with class D-s2,d2 external surfaces must maintain a 2.5 m distance from the primary residence unless they are fire-separated by an EI 60 [BD-60] structure.
- Integrated Structures: Garages or carports under the same roof construction as the primary house are considered integrated and are not governed by this annex, but by Annex 1a.
- Thatched Roofs (Stråtag): Unprotected thatched roofs require a minimum distance of 10.0 m to both property lines and primary buildings.
Documentation and Fire Safety Strategy
The building owner is responsible for ensuring compliance with fire safety regulations, regardless of whether a building permit is required. Documentation must verify that the chosen solutions align with the pre-accepted standards.
- Documentation for Brandklasse 1: Requires a situation plan showing distances to boundaries and other buildings, floor plans, and cross-sections.
- Certified Fire Advisor: A certified fire advisor (level 3 or 4) must be involved if more than five minor deviations from the pre-accepted solutions are made, or if the building is placed in Brandklasse 2.
- Execution Changes: Significant deviations during construction require new documentation and potentially a revised building permit from the municipal authority.
Rescue Service Access and Smoke Ventilation
Access for the rescue services (Redningsberedskabet) is mandatory to ensure effective firefighting and rescue operations. Specific dimensions for fire lanes and smoke ventilation openings are defined based on building size.
- Fire Lanes (Brandveje): Must be at least 3.0 m wide and cleared to a height of 3.4 m. They must support an axle load of 11.5 tons and a total vehicle weight of 18 tons.
- Hose Reach: Every part of the secondary building must be within 120 m of a fire lane, measured by hose pull distance, with at most 60 m being inside the building.
- Smoke Ventilation: Closed secondary buildings larger than 150 m² must have smoke ventilation openings equivalent to 0.5% of the floor area.
Frequently Asked Questions
When can a secondary building be built without a permit?
Under BR18 § 5, secondary structures up to 50 m² can be built without a permit if they comply with all building regulations and the pre-accepted solutions in Annex 1b.
What is the minimum distance for a carport to the property line?
An open carport with class BROOF(t2) roofing can be placed 1.0 m from the property line if the open facade does not face the boundary.
Does a garage require fire-rated walls?
If a garage is placed closer than 2.5 m to a primary building or property line, it typically requires fire separation rated at least EI 60 [BD-60].
What are the fire requirements for thatched roofs on outbuildings?
Unprotected thatched roofs must be at least 10.0 m from the property line. Protection can be achieved with an EI 30 [BD-30] under-roofing and 100mm cavity limits.
How wide must a driveway be for emergency vehicles?
A designated fire lane must have a minimum width of 3.0 m and be capable of supporting heavy rescue vehicles up to 18 tons.
What is the fire load limit for Risk Class 1 buildings?
The fire load for secondary buildings in Risk Class 1 must not exceed 1,600 MJ per square meter of floor area.
Are exits required for secondary structures?
Secondary buildings must have at least one exit directly to ground level. If the building exceeds 150 m², it must have at least two exits in opposite ends.
Who can document fire safety for Brandklasse 2?
For Brandklasse 2, a certified fire advisor must be involved to document that the fire safety level is maintained despite deviations.
