Lattice timber structures, which are made of elements connected by punched steel plates, are widely used for residential and industrial buildings. The main types of the structures are trusses, frames, and arches, which enables covering spans up to 30 m and more. The behavior of structures on fire plays an important role in the design process of the structures. The cylindrical roof with a 30 m span and the main load-bearing structures of lattice arches with elements connected by punched metal plates was considered as an object of investigation. The rational geometrical parameters of a lattice timber arch with punched steel plated joints were evaluated. Fire resistance and a possibility to increase it for an arch-type timber roof was also considered. It was obtained that using a protective layer is a preferable method of a fire resistance increase for the lattice timber arch due to arch joints; the material consumption was also increased by 1.65 times. It was shown that the rational values of the height of the arch, depth of the arch cross-section, and distance between the nodes on the top chord are equal to 7.85, 1.10, and 0.95 m respectively.