Standard 11: "Conserve the heritage value and character-defining elements when creating any new additions to an historic place or any related new construction. Make the new work physically and visually compatible with, subordinate to and distinguishable from the historic place."
"Standard 12: "Create any new additions or related new construction so that the essential form and integrity of an historic place will not be impaired if the new work is removed in the future."
Also important is Section 4.3.6 on Entrances, Porches and Balconies.
Thin black railings are common in the Mission Revival Style. The most ideal new balcony in this case would be to propose for thin metal railings that would appear light and discreet, while being compatible with the Mission Revival Style. However, these thin railings (potentially of ¼" balusters and thin guards) are not available unless custom fabricated, which would require an Engineer to prepare the drawings and specialized fabrication. This option was not preferred by the Owner due to associated costs and was not explored.
The Owner instead provided two options with either an Aluminum Railing systems through Ironex or a Durarail Glass railing system that would be available pre