Boathouse Roof Design . The solution was our coach house model. Designed on a 14’ x 14’ grid with a sidewall that measures 18’, there’s a total of 3,920 sq. Boat Dock Roof Styles Dock Builders Marine Specialties Inc from marinespecialties.net The ground floor is home to three boat slips and a dock at lake level. This two floor boathouse is on a floating platform and has its space defined for it. Look for wood that is rot resistant and impervious to insect damage.