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1. Does the City have information on what other homeowners have done to make their homes safer?

Most earthquake retrofits have involved improving the connection of the house to the foundation. This has been accomplished through use of metal straps, anchors, bolts, lags screws and/or nails to connect the wood sole plate to the foundation. This is probably the first area that should be retrofitted when considering and earthquake upgrade. In an earthquake, a house that is not connected to the foundation has a tendency to move or ‘walk-off’ the foundation, causing severe and sometimes irreparable damage. Even if the building itself is strong enough to withstand the motion, without a good connection to the foundation the rest is pointless.

Note: Typical building codes used in the State since 1960 have had a requirement that the foundation sole plate be anchored to the foundation by ½ - inch diameter bolts space six-feet apart along the foundation wall. Depending on the type of floor construction, you may not be able to see if these bolts exist (especially in a ‘post and beam’ type floor system where the sub-floor boards or plywood are nailed directly to the sole plate, covering the top of the bolt and nut). See Structural Mitigation for information on anchorage foundations and other earthquake retrofit information.

2. After what year of build date are most homes considered safe because of code requirements for seismic activity?

Homes built prior to 1960 are probably in the most need of verification that they are anchored by bolts to the foundation walls. Starting the mid 1970’s, the State of Oregon improved the building code and inspection process by mandating a single State-wide Building Code for builders to follow, and certification (through experience and training ) of building inspectors. It was not until the late 1980’s that earthquake resistant construction became commonplace, so homes built since that time have anchorage of the building to the foundation and wall bracing as an integral part of the design, construction and inspection requirements.
Note: even though a home is built to the most current earthquake standards, there is no guarantee that in a severe earthquake the building won’t sustain damage (no building can be guaranteed earthquake-proof). The purpose of earthquake building codes is to have the building resist the earthquake movement long enough for the occupants to be able to escape to the outside. The intensity and duration of an earthquake (in any combination) have a lot to do with how much damage is experienced.

3. I live in a three story town home. What seismic improvements might it need?

These types of buildings are relatively new to the Beaverton area. Most were built beginning in the late 1980’s. Most have been constructed to modern Building Codes and are earthquake resistant with positive connection of the building to the foundation and walls designed to brace against movement, so there probably is not a lot of earthquake retrofit that can be done. If the building is older, then verifying the building is anchored to the foundation is the first place to start. If the building was built before the late 1980’s, then wall bracing (especially on the bottom level at the garage doors or similar large openings) would be another area to consider.

4. If my home has high beamed ceilings, what supports if any is recommended?

In an earthquake it is not support that is the issue, it is connection. Making sure that beams are connected to the posts and the posts are connected to the foundation is an area where a retrofit would to better resist earthquakes. This could be done with various metal straps, hangers, anchors, ties, bolts, lag screws and nails. Home improvement stores usually carry an assortment of metal straps, anchors, ties, hangers, ties, bolts and lag screws for various connection conditions, there are even some that are decorative in nature, so if they are exposed they have a less utilitarian look.

5. Should furnaces be attached to the walls like water heaters?

Furnaces are required to be anchored in an approved manner which typically is per the approved manufacturer’s installation instructions. That usually involves screws or similar anchors connecting the furnace to the plenum boxes at the top and bottom of the furnace. In some cases it may also be connected by straps or similar material to the wall framing. If one chooses to add additional strapping, care must be taken to make sure the furnace is not damaged (as in piercing the combustion chamber, electronics, vents, fans, etc.). If possible check with the manufacturer about methods to better anchor the furnace (you don’t want to void any warranty).

6. Our wood stove sits in the middle of the room and has at least a 10 foot section of pipe to the ceiling. What recommendations are there to better resist earthquakes?

Objects like a wood stove can move around in an earthquake and could cause the chimney pipe to dislodge, so anchoring the wood stove to the floor would be the best way to minimize movement.

7. How are deck supports upgraded to earthquake standards?

The best way is to make sure that the posts are connected to the footings, the beams are connected to the posts, the joist are connected to the leger board and the ledger board is connected to the house framing and/or foundation. Also, brace the posts to resist movement. Good examples of how to accomplish this can be found in the City's Typical Deck Plans.

For ledger board attachment, see page12 (figures 5, 6 and 7).

For lateral load connection of deck joists to floor joists, see page13 (figure 6a).

Attachment of the ledger board is the most important (even to ensure the ledger won’t dislodge during normal use from people standing, sitting and walking on the deck). It is very important to make sure to add lag screws or bolts to the connection if it has only been attached with nails.

For cross bracing of posts, see page 17.

For connections of joist, beams and posts, see pages 18-20.
Home improvement stores usually carry an assortment of metal straps, ties, hangers, ties, bolts and lag screws referenced in the document.

8. Should I worry about trees, Doug firs, near my home in an earthquake?

Healthy established trees are not likely to fall during an earthquake.

9. Does Beaverton offer some sort of certification on the work that will be reflected in the property record for the benefit of a future sale?

The City will issue building permits for earthquake retrofit work and provide an inspection report for the work that was done (the City would also keep a permanent record of the permit and inspections). The report would reflect the level of work that was done. For example: If the work is for installing anchor bolts, plates and/or straps to improve the connection of the house to the foundation, but is not based on an engineered design, the permit and inspections will state: “Voluntary non-engineered seismic upgrade to improve the lateral force resistance and/or anchorage of the building. The installation only validates the anchors, plates, straps, etc. are installed as recommended by the manufacturers, and does not represent a seismic upgrade meeting the requirements of the State Building Code.” If the work involved a full engineering analysis (from a design professional) to meet a minimum earthquake resistance standard, then the permits and inspections would reflect that level of retrofit.