In the aftermath of the Nisqually Earthquake, the City of Seattle
strongly recommends that owners of unreinforced masonry buildings
who have not yet done so have the parapets of those buildings
thoroughly inspected for damage and deterioration before this
winter. A cursory inspection, particularly from street level, can
miss significant damage to the parapet and similar appendages, such
as cornices, spires and towers. "It is highly possible that
these types of parapets were weakened by the February earthquake,
and the freezing and thawing of our winter precipitation
could cause them to fall," said Craig Ladiser, DCLU
deputy Director for Operations. "These building features should
be repaired or braced as necessary as soon as possible to mitigate
the potential falling hazards."
The Seattle Building Code requires repairs for this type of
damage and deterioration. A licensed engineer or masonry contractor
can perform the inspection and a licensed engineer must develop the
plans for any needed repairs. It is important to note that Seattle
building owners have already had many of these buildings inspected,
and repaired as needed.
The cost of repairing parapets varies, commonly in the range
of $10,000 to $50,000. A building permit from DCLU is required
and DCLU staff is ready to discuss and review earthquake repair
plans. In some cases approval by an historic preservation board
is also required. For most projects plans can be approved within
To apply for a parapet repair permit,
please contact the DCLU Applicant
Service Center, located on the 20th floor of Key Tower at
700 5th Avenue, (206) 684-8850.
Unreinforced brick masonry (URM) bearing
wall buildings typically have multi-thickness (or multi-wythe)
exterior walls that support the floors and roof. This was
a common type of construction in older commercial buildings.
These masonry bearing walls usually differ in appearance
from masonry veneer by the presence of arched windows and
header bricks. Header bricks are courses of bricks with
the ends showing, used to tie the wall together. The floor
and roof system can be wood, steel, or concrete.
A significant weakness in older URM buildings
is the parapet, that part of the wall that is above the
roofline. It gets whipped back and forth in the earthquake
and can be significantly damaged without falling. Many buildings
did not shake quite hard enough or long enough during the
Nisqually Earthquake for a complete falling failure to happen,
but may still pose a danger to people and property below.
A severe winter with freeze/thaw cycles may cause further
damage to the parapet, and cause it to fail completely.
To mitigate the major falling hazard and
potential life-safety threat of URM parapets, lateral support
with steel braces are typically installed. It is recommended
that all URM parapets that extend above the highest anchorage
level to a height that is more than 1.5 times the thickness
of the parapet be braced.