One step closer to a Full-Scale Test of Thatched Facades

Published: 25.02.25

Two additional scaled-down facade tests of thatched constructions have been conducted as part of the latest MUDP project, which aims to develop modular multi-story buildings using biogenic materials. A full-scale facade test is planned for later this year.

The second round of fire tests in the project ‘The Biogenic Industrialised Construction – Construction, Fire and Architecture’ has just taken place. The first round included tests of three exterior wall constructions made from different wood variants, thatched facade solutions, and clay as a fire retardant. In the latest test round, two optimized variants of the selected construction from the first round were tested.

The project is carried out in collaboration with CINARK at the Royal Danish Academy, and aims to develop and fire-test prefabricated constructions made of biogenic materials, scaled for modular multi-story buildings. It is part of DBI’s contribution to the green transition in the construction industry. The project builds on the results of the previous MUDP project, ‘Thatched Facades for the Green Transition’.

“The construction we chose to proceed with from the first test round consisted of facade elements without clay impregnation. It was tightly thatched, which partially compresses the air in the thatching reeds and limits fire spread. We tested two improved variants of this construction,” says Mia Fossing Frederiksen, Project Manager for DBI’s part of the project.

Similarities between the two constructions

Both optimized constructions were made of thin thatch without clay impregnation and included a wooden panel and a timber cassette with straw on the back, forming the load-bearing structure of the modules. Additionally, both constructions had a flame deflector to prevent fire from spreading upwards. A layer of seagrass mixed with clay was added just below the flame deflector, as this point was expected to be the most exposed during the fire test. Furthermore, both constructions were thatched more densely at the edges than in the first tests to anticipate flame movement in the joints.

Both tests were also conducted under increased fire exposure, with a power level of 300 kW – compared to just 100 kW in the first round. Each test lasted 60 minutes.

Differences between the two constructions

Despite their similarities, the two constructions also had notable differences. The first construction used non-combustible composite panels as the flame deflector, preventing heat from penetrating the structure and stopping the fire from reaching above the deflector. The second construction, however, used a metal flame deflector, which conducted heat into the structure, igniting the wooden panel on the back. This caused the fire to bypass the deflector and spread to the upper cassettes in the last 10 minutes of the test.

“For the first construction, we added a clay panel between the wooden panel and the timber cassette with straw at the back for extra protection. The clay panel performed as expected and helped the construction burn in a more controlled manner,” says Mia Fossing Frederiksen.

“The second construction had no clay panel but instead had clay applied to the joints, as these had shown weaknesses in the first test round and needed reinforcement. Joints can significantly impact fire development. This construction burned faster than the first, confirming that both the clay panel on the back and the composite flame deflector were effective solutions,” she adds.

Full-scale test ahead

The next step is to further optimize the best-performing construction from the latest test round. Other factors such as buildability and resistance to rain and moisture will also be considered. One key adjustment is modifying the angle of the flame deflector to prevent water from pooling on it and instead direct it away from the construction.

“We are very encouraged by the initial test results. Now, we just need to finalize the measurements and then optimize one of the constructions before conducting additional scaled-down tests. The plan remains to eventually carry out a full-scale test,” says Mia Fossing Frederiksen, adding:

“Our goal is still to develop a construction that can serve as a basis for fire consultants in fire classes 3 and 4 when making approval decisions for building projects.”

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