Practical Engineering: Resisting Tornado Damage,
A breach in the garage door opening of this home first
pressurized the inside of the garage, resulting in devastating
failure of the garage walls and the home's roof. In a similarly
built home nearby (bottom), the garage door was bowed outward
by the tornado's suction. The door held, preventing further
damage to the home.
This plywood-sheathed house (top) fared much better than
another home (bottom), which was sheathed with non-structural
rigid foam board. Rigid foam offers no racking resistance, and
little resistance to damage from flying debris.
Vinyl siding and extruded polystyrene sheathing were no
match for flying debris, which pierced holes in this
By contrast, the plywood sheathing on this home remains
intact, although the vinyl siding is in tatters. Though this
OSB sheathing also fared well, it couldn't completely stop a
An initial breach at a large window resulted in internal
pressurization and loss of the roof structure over the vaulted
ceiling of this stairway. The rafters had been toenailed in
Here, in a home still under construction, a breach resulted
because a pair of French doors were poorly fastened into the
The hold-down anchors weren't adequate to keep this home
from shifting 5 feet off its foundation.
The anchor bolts in this slab-on-grade foundation below were
located 20 feet on-center and had no washers; none of the
structure was left.