Page 637 - 2018 National Home Improvement

2018 National Home Improvement Estimator, All Rights Reserved Page 510

Gypsum Drywall
Minor cracks (to 1/8" wide) usually show up at taped panel joints, at the corners of wall openings, at
interior wall corners and where panels join corner bead or trim. Cut away any existing joint tape. Scrape
off loose joint compound. Then re-tape, re-texture, sand smooth, and re-paint.

Nail head pops can happen anywhere in a panel. Pull the nail. Set a drywall screw about 1" from the
original nail. Drive the replacement screw just deep enough to dimple but not tear the paper cover. Then
re-texture, sand and re-paint.

When shaking is severe, drywall panels can buckle or work loose from the framing. Heavily stressed
drywall panels develop an "X" pattern of ripples that extend diagonally from one corner to the opposite
corner across the face of the board. If the surface of drywall has ripples or if cracks extend through the
board, it's best to remove the damaged section. If a large section is damaged, remove the entire panel. If
damage is limited to a small area, strip off a section 48" high and wide enough to expose the middle of
the stud or joist on each side. Cut a section of board to fit the opening. Apply the replacement section
with drywall screws. Tape, texture, sand and finish.

Fireplaces and Chimneys
Masonry fireplaces and chimneys are usually built on a separate foundation and are intended to be
self-supporting. Most masonry chimneys built before about 1930 have mortar made from lime rather than
Portland cement. Lime mortar is weak. Any chimney with lime mortar is a good candidate for
replacement. To check for lime mortar, scratch the surface of a joint with a screwdriver. If you cut into
the joint, it's made with lime mortar.

Today, most fireplaces in seismic zones are prefabricated metal. An insulated sheet metal flue is
enclosed with wood-frame walls. The finish can be stone or masonry veneer or stucco. A prefabricated
firebox and chimney, such as in Figure 18-14, has little risk of earthquake damage.

Chimneys strapped to the main building, as in Figure 18-10, aren't likely to topple over. But a strapped
chimney that isn't adequately reinforced can still fracture. If you see cracks in a chimney, shine a
flashlight down the chimney to c the flue lining for visible damaged. Broken flue tile will be a fire hazard
the next time there's a fire in the fireplace.

A masonry firebox at the base of a chimney can develop minor cracks under stress from an earthquake.
These cracks don't present a fire hazard. But stress from earth movement can snap masonry at the
point where the fire box joins the chimney. If you see cracks at this point or suspect damage to the
chimney flue, build a smoky fire in the fireplace and check for smoke leaking from the chimney.