Nailing Down the Need for Anchor Bolts in Seismic Safety

Question: The home inspector we hired seemed to do a very thorough job, with one exception: He gave us no information about the seismic stability of the home we’re buying. When we asked him about anchor bolts, he said there’s no way to inspect anchor bolts in a slab home because the bolts are concealed within the walls. He also mentioned that anchor bolts do not ensure overall stability of a structure.

What can we do to be sure our home meets earthquake safety codes? Should we insist on inspection of the anchor bolts?

Answer: Seismic safety requirements have been evolving for many years, with upgrades to building codes usually occurring after serious quakes. Anchor bolts were added to the code in the late 1930s, along with some foundation and framing upgrades, primarily in response to a major shaker in the Long Beach area.

For nearly 50 years thereafter, anchor bolts were regarded as an adequate means of securing a building to its foundation. Other than an increase in the number of bolts required, no significant seismic upgrades were added to the code during that time.

During the last decade, however, heavy-duty quakes have revealed that anchor bolts do little more than hold the sill plate to the foundation. The sill plate is the first piece of lumber that is set upon the foundation. In older homes, the rest of the structural frame is merely nailed to the sill plate.

In recent quakes, it was observed that a house could be dislodged from its foundation while the sill plate remained bolted in place. In response to this weakness, the building code was changed, requiring additional hardware and bracing to secure the framing to the foundation.

In most cases, structural displacement during quakes occurred with homes on raised foundations, rather than those on concrete slabs. This was because many raised foundation systems include short-framed walls (commonly known as “cripple walls”) between the floor and the foundation. The lack of bracing on cripple walls allows them to rack and lean during quakes, often causing severe structural damage.

With concrete slab foundations, there are no cripple walls. The only perimeter walls are those that encompass the dwelling space itself. Outside walls on a slab foundation tend to be more stable because of their attachment to the intersecting interior walls and also because the drywall or plaster surfaces act as a form of bracing. Thus, slab homes were found to be more stable in quakes, generally incurring less damage than homes on conventional raised foundations.

Home buyers are often concerned about seismic reinforcement and often seek confirmation of adequacy from their home inspectors. With homes on raised foundations, evaluation is generally not a problem, because the foundations and seismic systems are usually visible for inspection beneath the building.

However, as you learned from your inspector, anchor bolts are commonly not visible in a slab building, because that portion of the construction is totally concealed behind wall coverings. Exceptions may be found in the open framing of older garages, at plumbing access openings for bathtubs and air plenums beneath forced-air furnaces.

Although inspection of anchor bolts may not be possible at the home you are buying, major concern is unwarranted. The omission of anchor bolts in a contemporary dwelling is extremely unlikely. Their use has been a routine practice in residential construction for more than half a century, and verification of anchor bolts during the construction process is standard in a municipal inspection.

Insistence upon verification of anchor bolts at this time would require cutting open some of the wall surfaces, which would involve excessive work and needless expense. Such measures exceed reasonable prudence for a home buyer.

HEAD Asbestos Tiles Need Careful Assessment

Q: When we bought our house, the home inspector said that the kitchen floor tiles might contain asbestos. Now we are remodeling, and our contractor refuses to remove the tiles because he is not licensed to handle asbestos. He explained that asbestos tile removal is very expensive, and we’re trying to keep this project within a strict budget. Are these tiles really hazardous? If so, what should we do to get rid of them?

A: Old asphalt floor tiles and the glues used to secure them are commonly known to contain asbestos. But these materials do not necessarily pose a serious health hazard. The essential point to remember is that asbestos fibers are unsafe only when released into the air.

In the case of floor tiles, the fibers are thoroughly encapsulated in a solid medium. Unless the tiles are cut, sanded or otherwise damaged, the fibers remain trapped in the material and do not become airborne. If the tiles on your floor need to be removed, the manner in which they are handled will determine whether any asbestos fibers are released.

Your contractor was wise to decline this work because removal of asbestos-containing materials is strictly regulated by state and federal laws. In most instances, only a licensed asbestos abatement contractor can legally remove such material, regardless of the level of health risk involved. However, flooring contractors are now permitted to remove some products if they are duly certified.

Fortunately, the cost of removing asbestos floor tiles is moderate, compared with the cost of removing other asbestos materials. But removal may not be necessary. You may be able to leave the tiles in place and simply install the new floor covering directly over them. The contractor who installs your new flooring can let you know if this is feasible.

HEAD Aluminum Common in 220-Volt Circuits

Q: Last week, I installed a new circuit breaker in my electric service panel. While doing this, I noticed that the 220-volt circuits are wired with aluminum. Unless I’m mistaken, aluminum wiring is a serious fire hazard.

No one mentioned this when I bought the house, not even my home inspector. I’ve written some hot letters to the sellers, their agent and the inspector, but would like your opinion before mailing them. Do you think I should make them pay to rewire these circuits?

A: Please cool off and tear up the angry correspondence. Aluminum wiring, in some instances, is known to be hazardous, but it is still commonly used for 220-volt circuits. If installed according to manufacturers’ specifications, it presents no significant fire hazard. In fact, most electric power companies use aluminum for their main service lines.

There are two primary rules governing the proper attachment of aluminum wires: The connecting terminals must be rated for aluminum wiring, and the wire ends should be treated with a special compound to prevent corrosion.

What concerns me is your reference to having installed a new circuit breaker in your electric service panel. Your lack of familiarity with electrical procedures indicates that you should delegate repairs and alterations to the practiced hands of a licensed electrical contractor. I strongly advise that your work be reviewed by a qualified professional. In the process, your aluminum circuits can be properly evaluated.

*

If you have questions or comments, contact Barry Stone through his Web site at https://www.housedetective.com.

*

Distributed by Access Media Group.