The Building Inspector, upon notification from the permit holder or his agent, shall make the following inspections of the building or structure and shall either approve that portion of the construction as completed, or shall notify the permit holder, or his agent that the work fails to comply with the requirements of the Municipal Code: Foundation inspection shall be made after trenches are excavated and the necessary forms erected; frame inspection shall be made after the roof, framing, fire-blocking, and backing is in place and all pipes, chimneys, and vents are complete; and final inspection shall be made after the building is completed and ready for occupancy. It shall be unlawful for any person to do work, or cause work to be done beyond the point indicated in each successive inspection without the written approval of the Building Inspector.