All permits, except conditional use permits and stipulated shoreland permits, shall be granted or denied in writing, within 30 days after application, by the Department of Planning and Development. All stipulated shoreland permits shall be granted or denied within 60 days after application, unless the time is extended by mutual agreement. The applicant shall post any permit granted in a conspicuous place at the site. All zoning permits shall expire within 18 months, except for permits issued in the FPO zoning district which shall expire within 6 months of issuance. The permit may be extended for a maximum of 6 months for good and sufficient cause. Any permit issued in conflict with the provisions of this ordinance shall be null and void. [Code § 12.05-3.]