In 1936 at about the same time as Fallingwater and The Johnson Wax Building, Frank Lloyd Wright designed for Herbert and Katherine Jacobs of Madison, WI his first Usonian house. The Jacobs House I is considered one of the twenty most important houses in the U.S. by the American Institute of Architects, inspiring the wildly popular ranch-style home prevalent in the Post World War II housing boom.
Wright considered his Usonians to be of and for the American middle-class people and a break from the European influence of nearly all homes in America before it. There is no one feature which is truly unique to the Usonian designs, but rather there is a collection of features which distinguishes them.
- The house is sited to the front of the lot more than is typical, leaving a spacious private area to the rear for family use. Hajjar widely followed this principle, sometimes leaving very small front yards on an otherwise spacious lot.
- A carport was used rather than a garage (although the cantilevered roof often designed was probably more expensive than a garage would have been). Hajjar had less clout in telling his clients what they would get than Wright. He most often used garages, but also utilized carports as well as only a parking pad.
- The entryway was somewhat hidden rather than being an enhanced feature of the design. Often the entryway was from the carport. Hajjar went even further than Wright in this regard, even moving the main entrance to the rear of the house. Most often Hajjar's entry was from a breezeway to the garage. Some current owners are quite frustrated by visitors not being able to find the main entrance.
- The house was built on a slab with radiant heat in the floor. Hajjar built all of his homes on slabs with radiant heat with the exception of his experimental "cube" houses. Hajjar homes were all multi-story, however, with one exception. On the upper levels, radiant heating pipes were incorporated into the ceiling. The radiant heating has often been a source of problems, although most home owners love it.
- The main living area of the house featured an open floor plan with the relatively large living area flowing into the dining area which flowed into the kitchen. Hajjar's homes without exception follow an open floor plan for the main living areas, although kitchens could sometimes be closed off, generally with folding screens.
- The main living area featured floor to ceiling window walls to enhance the feeling of being in the outdoors. A house would not be a Hajjar design if it did not have prominent window walls. Even his apartments had mini window walls utilizing sliding glass doors.
- The feeling of being outdoors was extended by using the same wall and/or floor materials on the inside as well as the outside of the home and continuing the window wall to the wall of the house. This design technique is found only in Hajjar's more expensive homes, generally in a wing to his basic shoe box.
- Privacy was also important and was enhanced with rear landscaping. One feels almost in a county setting from inside Hajjar homes.
- Building materials generally used only on home exteriors were utilized throughout interiors, especially brick and native stone. Hajjar again went even further than Wright, using common cement blocks and even roofing shingles on interior walls. His favorite material for this was California redwood.
- Bedrooms were relatively small and intended mainly just for sleeping; they did feature a closet wall and sometimes a small desk space. Again Hajjar followed Wright's lead, especially in his less expensive designs.
- Kitchens like bedrooms were also relatively small, but it's thought that Wright never did any cooking. Most Hajjar kitchens are on the small side, although his "cube" houses did feature a breakfast area. Generally there was floor to ceiling storage in the kitchen.
- With no basement under the slab and no attic above the cathedral ceilings, there was little room for out of season storage. Except for himself, Wright believed that people collected too many things. Ditto for basic Hajjar homes. Occupants are still finding ways fifty years later to extend storage space.
- Wright was notorious for badly leaking roofs, primarily because of flat or low-pitch design. Hajjar took leaky roofs to a new extreme when he even used a V-pitched roof with drainage through interior walls.
- Mortar in masonry walls was flush vertically and indented horizontally to emphasize the low lines of the house. While Hajjar's homes were primarily wood, he did frequently utilize this technique.
- No gutters were used around the roofs as Wright thought that gutters were ugly and detracted from the design of the house. Again ditto for Hajjar, although gutters have been added to the majority of his houses to alleviate frequent drainage problems; they generally do look tacked on.