Page 636 - 2018 National Home Improvement

2018 National Home Improvement Estimator, All Rights Reserved Page 509

The Cape Mendocino earthquake of April 25, 1992 left the first floor of the home in Figure 18-13
displaced about 6 inches to the left. Notice the shape of the garage door opening.

You'll seldom see damage this obvious. Use a spirit level to check walls for plumb. Earthquake damage
will usually leave most walls out of plumb in the same direction. Use a framing square to check
openings for square. If windows or doors no longer fit the frame or bind when opened and closed, the
wall probably needs to be straightened. In general, any 8' wall more than 1/2" out of vertical alignment
needs repair.

To straighten a wood-frame wall, remove the finish on one side. Set wedge bracing or jackposts and
jack the wall back into alignment. (Notice the wedge brace at the left in Figure 18-13.) When re-aligned
and when windows and doors operate normally, re-nail the framing connections and install either
diagonal blocking, let-in wall bracing or structural grade shear panels. Shear panels nailed every 4" at
the base and top of each panel should prevent similar damage from future earthquakes. Then re-install
the wall finish.

Cracks in Plaster and Stucco
Most movement of ground during an earthquake is lateral - left and then right. Lateral movement in a
frame building creates horizontal cracks starting at the corners of framed openings such as doors and
windows. On interior walls, you'll see a pattern of similar cracks on both sides of the wall. If you see
cracks running at random or mostly vertical on a plaster or stucco wall, expect that the cause is settling
or shrinkage of framing members rather than an earthquake.

Don't bother patching hairline cracks in stucco or plaster. A good coat of paint will fill and cover cracks
no wider than the stroke from a ballpoint pen (1/64"). Any crack wide enough to insert the blade of a
table knife is a candidate for repair.

Scribe out the crack with the tip of a screwdriver, putty knife or a linoleum blade. Cut deep enough to
get down to the brown coat. On exteriors, fill the crack with premixed stucco patch. On interior
surfaces, use premixed spackling compound. Several thin coats are better than a single thick coat.
Sand when dry and then repaint.

According to The General Guidelines for the Assessment and Repair of Earthquake Damage published
by CUREE (The Consortium of Universities for Research in Earthquake Engineering), building paper
under a stucco finish is far more flexible than the stucco itself. Even where the stucco is badly fractured,
tears in the building paper are unlikely. If the stucco can be repaired without being removed, don't worry
about vapor barrier under the stucco. No inspection of the building paper is required.