The city of Glendora, in Southern California, has adopted a historic district which is made up of approximately 100 Craftsman-style residences. The city created a design handbook to aid residents in rehabilitating and expanding their homes.
One area which the handbook lacks is a discussion of what constitutes a significant alteration. We reference the Sec. of the Interior's Standards for Rehabilitation in determining whether or not the alterations are appropriate. The handbook also describes character-defining features for the various architectural stlyes found in Glendora. We use both these resources to determine the appropriateness of the alteration.
Can anyone recommend certain books or resources which might aid us in determining whether or not an alteration would be appropriate?