Roof Thrust
Overestimated
To the Editor:
Gordon Tully's short piece (Building
with Style, 2/91) on building second
stories with half-walls, or knee
walls, was a good, concise primer on
outward roof thrust and how to deal
with it. A few things puzzled me,
though.
First, a second-floor ledger lag
screwed into the studs seems like a
poor way to resist outward thrust. If
the thrust exists, it would be pulling
on the threads of the lag screws —
not a very positive connection. Second,
I wasn't sure why the article
mentioned, but then dismissed, the
alternative of anchoring each joist
sideways into a wall stud. It has some
inconveniences, as noted (you have
to line up each joist with a stud,