BRANZ TR9 timber-framed well or floor/ceiling systems
About this tool
TR9 is a specialist fire engineering tool used to extend the results of a fire resistance test on a light timber‑framed wall or floor/ceiling system.
When a prototype wall or floor system has passed a fire resistance test, TR9 allows designers to extrapolate those results to similar systems with:
- Greater wall heights
- Longer floor spans
- Different loadings.
This makes it possible to design timber‑framed walls and floor/ceiling systems for fire resistance without repeating full‑scale fire testing, provided the new design stays within defined limits.
Download this tool and user guides
How to use this tool
TR9 is provided as downloadable software with supporting guidance material.
To use the tool:
- Download and install the TR9 application
- Read the TR9 User Guide and Technical Recommendation to understand assumptions and limits
- Enter input data from the prototype fire resistance test
- Enter details for the proposed wall or floor/ceiling design.
Walls
For light timber‑framed walls, TR9:
- Models studs as axially loaded columns
- Accounts for loss of timber due to charring during fire
- Uses the tested system’s char factor to estimate reduced load‑bearing capacity
- Helps select new stud sizes to meet stability requirements at increased heights or loads.
Floor/ceiling systems
For timber floor/ceiling systems, TR9:
- Compares stresses in the proposed design with those in the tested system
- Allows span increases where induced stresses do not exceed the tested case
- Requires that applied loads do not exceed those used in the prototype test to maintain integrity.
The tool ensures that the performance criteria of stability, integrity and insulation demonstrated in the fire test remain satisfied in the extrapolated design.
Background
TR9 is based on BRANZ Technical Recommendation TR9, which sets out two extrapolation methods:
- One for light timber‑framed walls
- One for light timber‑framed floor/ceiling systems.
The method builds on BRANZ research into the fire performance of load bearing timber‑framed systems and uses established structural analysis principles combined with fire damage modelling, such as timber charring.
TR9 is intended for use by trained practitioners and relies on a successful prototype fire resistance test as its starting point. It provides a rational, performance‑based approach to fire resistance design while clearly defining the limits within which extrapolation is permitted.