Any changes typically go through a permitting process with L&I, and because it is listed on the historic register the Historic Commission must review and approve of changes.  If there is no impact to the exterior it is immediately approved by the Commission.  If it is not listed on the register (and so not protected from a future possible demolition!) then exterior changes must comply with the code under the Neighborhood conservation code. http://www.qvna.org/committees/NCD-Ordinance.pdf