Fire compartmentation and WBDBO calculations
Fire compartments limit how far a fire can spread. The Building Decree (Bbl) sets requirements for the size of fire compartments and for the resistance to fire spread between them, known in Dutch as WBDBO. We design a compartment layout that works for your building and calculate whether it meets the requirements. You know exactly which walls, floors, doors and façades need fire resistance, and which do not.
What is WBDBO?
WBDBO (weerstand tegen branddoorslag en brandoverslag) is the resistance to fire spread from one fire compartment to another, or to a neighbouring plot. It is not the same as the fire resistance of a single wall or floor. A fire can also travel around a construction: through openings in the façade, or by heat radiation from flames and the smoke plume. A WBDBO calculation to NEN 6068 takes every route into account.
Why a precise calculation pays off
- No fire resistance where it is not needed — over-specified walls, doors and glazing add cost without adding safety.
- Enough fire resistance where it is needed — the weak spots are often in the façade or roof, not in the walls you can see.
- Design freedom — a well-chosen compartment layout leaves room for open floor plans, atria and large glazed façades.
- A smooth permit process — clear calculations that the municipality and the fire service can follow.
When you need it
- New builds and extensions, as part of the permit application
- Renovations and changes of use
- Façade changes, such as new cladding, glazing or openings
- Buildings close to a plot boundary or to neighbouring buildings
- Mixed-use buildings, such as apartments above shops or offices
- Large logistics and production buildings, where a larger fire compartment can be substantiated as an equivalent solution using NEN 6060 or the risk-based approach of NEN 6079
What you get
- A compartmentation drawing showing fire compartments, sub-fire compartments and escape routes
- A WBDBO calculation to NEN 6068 for every relevant route
- The required fire resistance per construction element, door and façade section
- Concrete recommendations where the design does not yet comply
- A clear report in English that the municipality and the fire service can assess
How we work
- Intake — we discuss the building, its use and your plans, and collect the drawings.
- Compartment layout — we determine the most suitable layout of fire compartments and sub-fire compartments.
- Calculate — we calculate the WBDBO for every relevant route and identify weak spots.
- Report and support — you receive a clear report, and we explain the results to the municipality and the fire service.
Frequently asked questions
How long does a WBDBO calculation take?
Usually around two weeks after we receive complete drawings.
Is WBDBO the same as fire resistance?
No. Fire resistance applies to a single wall, floor or door. WBDBO describes how long it takes a fire to spread from one fire compartment to another along every possible route, including routes through the outside air around a wall or floor.
Do existing buildings have to meet the same requirements as new builds?
No. The Bbl sets lighter requirements for existing buildings than for new builds. We assess your building against the level that actually applies, so you do not invest in more than is required.
What do you need from us?
Floor plans, sections and elevations, a site plan showing plot boundaries and neighbouring buildings, and information on the construction and materials of walls, floors, roofs and façades.
Related services
- Building plan assessment & fire safety plan — fire safety in every phase of the build.
- Escape route and evacuation capacity — how many people your building can safely hold.
- Fire safety inspection — we check on site whether compartmentation has been built correctly.
- CFD fire and smoke simulation — for buildings where the standard rules fall short.
Need a compartmentation plan or WBDBO calculation?
Send us your drawings and tell us about your plans. We will tell you what is needed and send you a proposal.