Mechanical fire resistance of internal load bearing walls under both-sides heating is important for the prevention of collapse of a dwelling in a fire. Feasibility of the 45 minutes mechanical fire resistance with Japanese traditional timber-frame soil internal wall is studied for this purpose. The tests were initiated with intermediate scale specimens for the examination of the charring and internal temperature field of the column and then loaded tests under both-sides exposure were conducted on two 1-story tall bare-timber wall specimens. The tests suggest significant influence of the mortises of columns for horizontal timber bars on the buckling of walls. The conventional predictive method of the mechanical fire resistance of bare timber walls is then modified for the tested configuration.
