Signs for lawfully permitted nonprofit chartered membership organizations, farms, public buildings, playgrounds, golf clubs and the offices of charitable organizations shall be facade signs of a maximum of 200 square feet of sign area or 10% of the building facade and 5% of a secondary facade, whichever is less. Facade signs shall consist of individual noninternally illuminated letters, mounted directly on the building facade. The signage letters can be illuminated only by indirect shielded, nonflashing light. Ground signs are also permitted of a maximum size of 32 square feet on either side.