Chicago Frame

Siegfried Gideon alleges this type of construction was invented by George W. Snow in 1932 for the Saint Mary’s church in Chicago. The origin has been contested, but it is clear that this construction method departed from the traditional heavy timber frame concept of posts and beams. The building relies on many small structural elements that create a strong and rigid structure by only carrying a small amount of force in each member. In distinction from what is commonly known as a Balloon Frame construction method, this model retains some elements of heavy timber construction.

The defining characteristics of the Chicago Frame are a thick sill plate (8” x 8” or larger) that is halved at the corners, with light timber studs (2”x4”) that are mortised into the sill. The studs run the entire height of the building, if there is a second story, the joists are held by a ribbon board that is rebated into the studs. The joists are also of significant member size and are partially mortised into the sill.