On the Level

Cheap Fixes Prior to the Big One

by Terry F. Meany

An earthquake could happen at anytime. When enough plates have shifted and the eight local, active faults rupture, it’s a shake, rattle and roll moment and a little late to think about seismic improvements to your building. The U.S. Geological Survey, among others, believes there is a 62% probability of at least one 6.7 or greater quake occurring in the Bay Area before 2032. Of course, no one knows when; we can only estimate, guess and toss Tarot cards. Some planning and relatively inexpensive retrofits to your buildings will keep your tenants safer and help preserve your property.

Some things you have no control over, such as your building settling into soft soil during a quake—an infamous quality of the Marina district. As soft soil liquefies and buildings descend, gas lines break and the resulting fires cause much of the damage in an earthquake’s aftermath. Combine this with broken water pipes, and swift fire containment is a little iffy.

The least safe buildings during an earthquake are those with unreinforced masonry; that is, structures without steel reinforcing bars within their masonry walls. These make up about 6% of all housing in San Francisco County. More common are two- and three-story wood-frame buildings with wood, stucco or occasionally brick exteriors. All in all, smaller wood buildings have the potential to ride out earthquakes fairly well due to their flexibility. But unless they’re bolted to their foundations and have strong shear walls—more on these later—the shaking can send them slip-sliding away. Wood construction entails so many fastened wood-framing members that the energy, in the form of shaking from an earthquake, is absorbed through many pathways, distributing the force and helping to dissipate it.

As a building owner, you can address structural reinforcement, secure gas and water lines, and educate your tenants regarding their responsibilities in the event of an earthquake.

Structural Fixes
According to the USGS, fewer than 10% of Bay Area homeowners have retrofitted their homes for earthquake protection. Some no doubt figure it’s lasted this long, so it’s probably OK. Maybe it is, but you’ll never know until it goes through the Big One.

The key changes in seismic retrofitting are bolting the building to its foundation and constructing shear walls. Proper fasteners, along with their placement and spacing, must be employed. Shear walls, which are essentially plywood fastened to wall studs, call for specific nail sizes and nailing patterns. Together, they help prevent damage from sideways forces called racking and shear.

The ideal shear wall would be solid, without any window, door or garage openings, and would be the entire height of a building. Well, that’s grand if you want to live inside a three-story bat cave. More likely, you’ll have a cripple wall—the framing between the foundation and the first floor, often only a few feet tall—which should be reinforced, especially if your building is a so-called “soft-story” building, with residential or office space over a ground floor and openings for garage doors or large commercial windows instead of solid walls.

How Do You Reinforce?
Assuming your cripple wall is exposed, reinforcement is fairly straightforward. First, install two-by-four blocking between the studs and into the mudsill, which sits on top of the foundation. These help prevent the bottoms of the studs from racking loose. Next, install approved expansion bolts or an epoxy anchoring system through the blocks and mud sill and into the foundation. Expansion bolts work best in strong concrete while epoxy anchors are recommended for questionable concrete and brick foundations, which can crack when expansion bolts are tightened. Either fastener is installed about every four feet on center, although closer spacing is called for with weaker foundations or for larger buildings.

After securing the mudsill, structural plywood sheathing is nailed to the cripple walls. Be sure to do the sheathing after any wiring and plumbing projects that need to run through these studs have been completed and inspected. To prevent moisture buildup, three-inch vent holes are drilled into the top and bottom of the plywood sheets and covered with screening to control rodents.

The final work is to tie the top plates of the cripple walls to the overhead floor joists with shear transfer ties.

What happens if you have a tight crawl space? Special L-shaped steel connectors are available to tie the cripple wall to the foundation. If you have a brick foundation in iffy condition, you’ll hear the scariest words a foundation contractor will ever say: “We need to replace it.” This doesn’t necessarily mean jacking the building up, removing the old foundation and pouring a new foundation. New foundations can be successfully poured and installed next to existing ones, but you’ll have to haggle this one out with an engineer first. A less-than-iffy brick foundation can be strengthened with a concrete cap or coating on the exposed sides, but the cap must be reinforced and properly installed to do any good at all. Just applying a slurry of concrete won’t keep loose bricks in place during a major earthquake.

Once the walls are beefed up, any posts, piers and beams need to be attended to as well. In older San Francisco buildings, the posts often rest on piers without being secured and are only toe-nailed into the overhead beams. This could be seen as a matter-of-faith building style, but I’m all for steel connectors. Some contractors will temporarily brace the beam, remove the posts one at a time, install new concrete footings and piers with embedded straps for securing the bottom of the posts and replace the posts, often with new ones. A less expensive approach is to retain the existing posts and secure them to the concrete floor with large metal brackets designed for this purpose. In either case, the tops of the posts are attached to the beams using straps, ties or nailed-on plywood gussets. An alternative when retaining and reinforcing the existing posts is to install new, additional posts for extra support.

There is a minefield of hardware and fastener possibilities used in seismic work, any number of them wrong for this application. Contact an experienced contractor if you intend on subbing the work out or consult with an engineer specializing in seismic upgrades for hardware recommendations if you are doing the work yourself. Any number of well-meaning contractors attempt seismic improvements that might look very solid and safe, but they won’t cut it when you really need to depend on them. It’s something like drywall screws: they’re used for everything because they’re cheap and convenient, but there really are good reasons to use different types of screws for different applications.

Seismic upgrade work is voluntary; no one will twist your arm to do it or penalize you if you do not. Building inspectors can only check that the work was done according to plans; they cannot confirm the quality of those plans. The procedures are not especially complicated, but they require a permit and an inspection.

Cheap Fixes
California state law requires that all water heaters must be securely strapped to wall studs or another approved contact point. According to the California Seismic Safety Commission, “The easiest way to brace a water heater is to install a preapproved bracing system available at most hardware stores. Make sure it has the Division of the State Architect’s stamp of approval on the box before purchasing.” Other means are acceptable if done according to state guidelines (www.seismic.ca.gov/sscfaq.htm). Water heaters can be a vital source of drinking water if supply lines rupture during an earthquake, so it’s critical that they are well secured.

A variety of Velcro straps—the sticky end goes around the appliance or furniture, the other end is screwed to a wall stud—are available and should be used on all major appliances.

Replace any rusted or worn gas pipes that could come apart at connection points if your building starts shaking. Also, replace any rigid gas connections to appliances with flexible stainless-steel connectors. These decrease the chance of a break at the appliance. Consider installing excess-flow gas-shutoff valves for your appliances. These valves shut the gas off when they sense excess gas flowing downstream from them. They will not shut off the gas if slow leaks occur. Another choice is an earthquake-actuated valve, which shuts off the gas when it senses shaking in a building, although this type of valve does not distinguish between hazardous shaking and nonhazardous. Both these valves should be certified by the State Architect and should be installed under permit.

Check out your plaster ceilings. Deep cracks could indicate a sizable section of plaster ready to fall. Repairing plaster ceilings with new plaster is expensive, but a drywall patch is less costly. If nothing else, consider screwing some plaster washers in the iffy section to help secure it to the lath. There’s always the question of who’s responsible if both you and the tenant were aware of cracked ceilings and their collapse led to injuries. Although you want your tenants to exit their units as quickly as possible once it’s safe to do so, there could be fires. Be sure everyone has a fire extinguisher and knows how to use it.

The opinions expressed in this article are those of the author and do not necessarily reflect the viewpoint of SFAA or the San Francisco Apartment Magazine. Terry F. Meany is a former contractor and landlord. He is cost-conscious but not cheap and knows deferred maintenance always costs more in the end. He can be reached at tfmeany@msn.com. Copyright � 2006 by the San Francisco Apartment Magazine. All rights reserved.