Page 626 - 2018 National Home Improvement

2018 National Home Improvement Estimator, All Rights Reserved Page 499

What FEMA Recommends
FEMA has studied hundreds of structural failures caused by earthquakes. Many of these failures could
have been limited or eliminated entirely with a few straps, anchors or braces. Consider making the
changes recommended in this chapter any time you repair earthquake damage. Most of these changes
can be made at a very reasonable cost.

Here are the defects FEMA has cited as most common in older homes:
* missing or inadequate bolting to the foundation
* inadequate cripple wall bracing
* damage to bracing and finish materials
* excessive drift at garage fronts
* partial or complete collapse of hillside houses
* separation and loss of vertical support at "split-level" floor offsets
* damage and collapse of masonry chimneys

Nearly every older home in a seismic zone is a candidate for one or more of these improvements.

Foundation Bolting
Many houses constructed in California before 1950, and even later in other parts of the United States,
do not have anchor bolts that attach the wall bottom plate or foundation sill plate securely to the
foundation. During an earthquake, wood framing can slide off the foundation. If you're doing cosmetic
earthquake repairs in an older building, note the presence or absence of anchor bolts. IRC code section
403.1.6 requires a 1/2" anchor bolt embedded 7 inches into concrete every 6 feet.

If you don't find anchor bolts where expected, adding additional anchor bolts isn't particularly difficult or
expensive. Figure 18-2 suggests three good options. Drill expansion-type anchors into a reinforced
concrete or masonry foundation. Adhesive anchors are a good choice for use in unreinforced masonry or
weaker concrete foundations, but can be used with any type of foundation. Be sure to place a steel
plate washer under each anchor head.

If there isn't enough working area to drill an anchor bolt hole through the bottom plate and into the
foundation, use one of the other type of anchors shown in Figure 18-2. All of these anchors will transfer
horizontal earthquake loads from framing to the foundation.