Every roof sign, including its supporting structures, shall be so designed and constructed that it will safely withstand a horizontal wind load from any direction of twenty pounds per square foot of exposed surface in addition to its own weight, up to a height of forty-five feet above the ground. Working stresses shall not exceed those specified in the building code for the various materials. Every such sign shall have a factor of safety of two against overturning. In computing the resisting moment, dead loads shall be considered. No roof sign shall be supported by or braced by wooden beams or other wood construction of a building or structure over forty feet in height. (Ord. 89-3 (part), 1989)