Properties that have a local historic district designation usually must go through a design review process when changes to the property are proposed to make sure the changes meet the adopted design standards. This is in addition to any building permits that may be required. For example, if you want to add a garage to your house, before you could get the building permit for the garage you would have to submit your garage design to City staff or to the Historic District Commission. This way they can review the design and check that it meets the requirements. There may be requirements (like the garage being set behind the front of the house, or the roof of the new garage needing to match the roof on the existing house and using the same exterior materials). Once the design is approved, you can move forward with the building permit.
It’s important to note that ordinary maintenance and repair usually do not require design review approval – those are necessary items to keep the historic structure in good condition and do not need special approval.