Danbury developer Dan Bertram is seeking approval to add 12 single-family homes to The Ridgetop, a gated community off Clapboard Ridge Road near Danbury High School. The project would expand an existing cluster of eight homes on Damia Drive. The city’s wetlands commission is reviewing the 14-acre proposal, which includes a site walk and public hearing expected in October. If approved, construction could take about 18 months to complete.