Louis Kahn was known for his interest in Scottish Castles, by which he elaborated the distinction between ‘served’ and ‘servant spaces’, “with great central living halls and auxiliary spaces nestled into thick outside walls”. The castles were a strong inspiration for later works such as the Unitarian Church in Rochester and Erdman Hall at Bryn Mawr College.

Deep set shutters and a general work on the façade’s thickness were introduced during the design process of Fisher house. From the thesis “LOUIS I. KAHN’S FISHER HOUSE: A CASE STUDY ON THE ARCHITECTURAL DETAIL AND DESIGN INTENT by Pierson William Booher”:

“The ‘deep set shutters’ are a series of recessed window pockets, slight multifunctional intrusions into the space that give depth to the façade while creating an interior shelf. The most practical aspect of the window recessions is a sense of privacy and humanity they provide, creating variations along the facades that cast shadows and give a texture to the form. Not only do they break the planarity of the façade and bring the exterior inside, but they allow for an open window during a heavy rainstorm, as their form naturally protects against water infiltration.”

For more informations on the single castles, have a read at the Spanish “Tectonica Blog“: the guys there are doing a very thorough survey of construction types, among which you can find the “military” category.

Related, on Deconcrete:
Inhabit a Wall
(An intesting comparison between modern stadium and British fortresses).