Abstract: A timber frame structure was set up to conduct fire test studies on the factors affecting the fire spread between timber structure buildings. The study considered variables such as fire load density, size of exterior wall openings, combustibility of exterior wall materials, and horizontal spacing between two buildings. The results indicate that increasing the opening area of the external wall would significantly enhance the radiative heat flux on the target wall under identical fire load densities. Similarly, increasing the fire load density in the burning room would also amplify the radiative heat flux on the target wall under consistent opening conditions. Once ignition occurred in the exterior wall of the burning room, the target wall would be exposed to the combined radiation from the room opening and the external flame in the exterior wall, and this would potentially escalate fire spreading risks for the target wall. In the tested fire scenarios with a 6 m fire spacing, the radiative heat flux values on the target wall remain below 10 kW/m2, which did not pose a risk for fire spread between buildings due to radiation. These research results provide supportive data for quantitatively analyzing various factors' influence on building-to-building fire spread and aid in determining appropriate fire spacing between builds.

Key words: timber structure building; fire spread; radiation intensity; fire spacing; opening size； fire load density