Page 631 - 2018 National Home Improvement

2018 National Home Improvement Estimator, All Rights Reserved Page 504

If the chimney is outside the frame walls, consider wrapping steel straps around the outside of the
chimney. Figure 18-10 shows straps at the floor, ceiling and roof level. These straps will be exposed to
the elements, so use straps with corrosion protection. Straps aren't likely to reduce earthquake damage
to the chimney itself but will reduce the chance of injury due to falling debris.

Where the chimney extends well above the roof line, add a brace to connect the top of the chimney to
the roof surface.

A better choice is to replace a masonry fireplace and chimney with a factory-built fireplace and flue
surrounded by light-frame walls. Factory-built fireplaces and chimneys withstand earthquakes much
better than conventional masonry fireplaces and chimneys.

When Making Alterations
Consider earthquake risk any time you change or remove bracing from a wall, floor or roof. Even interior
remodeling projects can increase the risk of earthquake damage. Many interior walls actually provide
protection against earthquake and wind loads.

Figure 18-11 shows two popular remodeling projects that can add risk of earthquake damage. At the left
in Figure 18-11, dormer windows have been added to an existing roof. Any time you add an opening to
an existing roof, check the opening size against permitted maximum sizes in the IRC. Doubled rafters
and headers may be required to meet gravity load requirements.

At the right in Figure 18-11, a sun room has been added to the rear of a home. If you remove wall
bracing when making an alteration such as this, check the remaining wall braces to be sure location,
length and type of bracing comply with the IRC. More bracing will usually be required in walls on either
side of the alteration.

When Adding a Room
Additions to a home are either horizontal or vertical, or both. Figure 18-12 shows a horizontal addition
(upper drawing) and a vertical addition (lower drawing). Many horizontal additions built at the side of an
existing house will require reframing the roof, as shown in the upper drawing in Figure 18-12. Vertical
additions always require a change in the roof line.