Chicago Balloon Framing To the Editor: Regarding your article on collar ties by Harris Hyman (4/92): Chicago is where they say balloon framing got its start. I'm not sure whether this is true or not, but I have worked on a great number of attics with balloon-framed (cantilevered) kneewalls in this city. Invariably, all have been pushed outward by rafter forces over time. My theory is that when the carpenters installed the original collar ties, they nailed at the normal angle of hand and hammer and didn't try to get the nails in at 90 degrees to create the shear-pin effect needed. Over time (50 to 100 years) the rafters were able to pull away from the collar ties and