The part having the risk of fire spreading is a part of the building where there is a possibility of directly catching fire due to the spread of fire from the neighboring house or spread of fire due to the radiant heat from the fire. This definition is used in placing restrictions for the purpose of fire prevention, applicable to exterior wall, behind eaves, roof or opening etc. These parts are defined as located within 3m if on the first floor, or within 5m if on the second floor and above, measured away from: (1) Boundary line with adjacent property, (2) Center line of the road, and (3) Center line between the outer walls of two or more buildings on the same premises (buildings with a total area of 500 square meters or less are considered as one building). However, this excludes parts that are facing places effective for fire prevention, such as water surface, walls of fire resistant structure, and open spaces such as parks, plazas, rivers etc.