Do you rent or own in Oakland? Does it have some kind of problem? Have you ever wondered "what's wrong with my house?" Add your experiences and advice for house problems here.
Notes from Matt Cantor (ACI)'s presentation at Workshop Weekend 6/22/13 at Sudo Room with later edits to the seismic section by Andrew.
What do I need to know about seismic safety?
In the East Bay, approximately 90% of houses are not earthquake-ready. In North America, we are not at high threat of being in physical danger if we are in a house in an earthquake, but there is a high risk of property damage to the point where it won't be worth it to rebuild a house after an earthquake. Seismic retrofit can cost from $10-30k.
The Hayward Fault has had 7 major earthquakes in the last thousand years. They are spaced generally 140 years apart, at intervals ranging from 65 to 195 years. It's been more than that average since the last major earthquake on this fault, 1868. It is statistically likely that we will have a major (up to 7.0 magnitude) earthquake within the next 20 years on one of the Bay area's major faults. We are very close to the Hayward fault in Oakland.
In seismic zone, you don't want your building to be built out of breakable material. Ideal material is rubber! Brick is extremely brittle. In earthquakes, bricks want to blast apart.
Many houses from the early 1900s have a brick chimney going through the center of the house. Even if the rest of the house is wood or not brick, these chimneys are extremely dangerous in earthquake situations (bricks will want to explode from the bottom at up to 60mph). The bricks will come in contact with the wood and create even more problems. Houses made entirely out of brick (not just a brick front) are in high risk of high damage. If you have brick in a foundation, this will be dangerous. Brick foundations were used commonly until about 1914. Unreinforced masonry buildings are now illegal to build.
Just to keep in mind, Loma Prieta effects were based on an earthquake 100 miles away. Earthquake force decreases by the square of the distance. As you get further away, it drops way off and when you're close in, it is very powerful. Loma Prieta was in the mountains north of Watsonville & did a great deal of damage in Santa Cruz which was about 10 miles from there. Effects in the Bay Area were destructive in parts of San Francisco, Santa Rosa, and in Oakland on the Cypress Structure (it was built and engineered poorly for the soft ground. If there had been a nearby earthquake, it wouldn't have stood a chance). It was known that the eastern section of the Bay Bridge was vulnerable. In the Marina district in SF, part of it was built on fill (some of the city's fill includes abandoned ships from the Gold Rush!). That fill does not behave well in earthquakes because it is not very dense. Fill will jiggle and shake apart. If you make a pile of sand on a table and shake the table, the sand will spread apart. A pile of sand mixed with concrete on a table will not fall apart. The majority of Alameda is made of landfill.
What is a "soft story" condition? One of the most important things in a house, in terms of earthquake strength has no openings. You have solid wall all around and you are pinned down to the ground. The walls will bend uniformly and bounce back. If you cut out a hole in one side, making up much of one side. It will want to tear at those corners and want to fail. Garages on the ground floor, with 1-2 stories of heavy building on top, this is very dangerous. This is what happened in the Marina district. Find out if a building in Oakland is a soft story building at softstory.openoakland.org. The city has begun a slow-moving program that will require all multi-unit housing structures to be retrofitted.
The best foundation would be cement on all four sides.
Concrete is a way of trapping water to keep the material strong. We use sand as a filler. You can take 7 bags of concrete, 1 bag of Portland cement, and some sand and it will stay like this for thousands of years (ex: roman structures :)). Rebar is the metal within the concrete. If you make a long bar of concrete, it will want to bend. We use pieces of metal that are bumpy and when you cast concrete around it, concrete will hang onto it.
In earthquakes, houses on level ground rarely fail because the foundation was too weak. What is more important is for the box to stay connected around the perimeter and that walls are braced in a way that would let the walls bend and snap back.
If you have a garage or other big opening, you need to reinforce it. A moment frame - weld a steel frame around the opening and in the bottom, dig out big holes and put in two big footings and mount the bottom of that frame in there. This is all part of earthquake retrofitting.
If you have a house on top of a garage, in an earthquake, make sure that you know how to get out and are clear on the threat of fire damage.
Other problems in earthquakes - pipes want to snap and pull apart. Water heaters are dangerous.
Most people have a water heater tank. Every 20-40 mins the gas heater heats the water. After an earthquake, you will have a source of water - up to 40 gallons of clean water! Every time you turn on the hot water, the water flushes, so it cleans out almost every day.
Automatic gas seismic shutoff valve. Shuts off all the gas in the house automatically in case of the earthquake (because there is a danger of gas pipes exploding). Physical shutoff mechanisms turn off when they get shaken (~5.0). A plumber can install this. A great valve is the Little Firefighter :)
If you have a new house, best first priority for seismic safety is to get shutoff valve, enough carbon monoxide detectors, enough smoke detectors. This will provide basic protection against fire and explosions immediately after a large earthquake.
What are big, basic problems to target first to ensure seismic safety?
Lack of fasteners (bolts connecting the frame of the house to the foundation so it can't separate). Eliminate failure of cripple walls.
Wikipedia has a lot of really useful informating on seismic retrofitting.
Help! I have tilty floors!
The East Bay flats are largely beds of clay-bearing sediment. The distribution of clay may not be uniform under your house. This means that you might have cracks (that open and close over the year), tilting in your floor, and more. If you have this on a hillside, as it goes up and down with the rain, it will also push your house down the hill and your house will slide (potentially in different directions). This means that houses (especially wood-frame houses) can have "roller coaster" floors. Sometimes on the surface of concrete, ground, or under your house, if you see white powder, this is various salts, etc. have failed to evaporate as water subsided. If you have this in your basement, don't store things there because it will get water damage and mold.
Uneven floors don't matter very much for seismic issues. The house is not more vulnerable to damage.
Tilty room on the second floor may have been a porch area and may have been intended to drain. If the room below this is level, then it may have been built this way.
Alameda is different - it is mostly a beach - so underneath houses there, you will find sand.
How do we get the water to go around your house? A drainage system!
Roofs!
Tar and gravel roofs can start to fall apart within 10-20 years.
Shingle roofs can last from 20-40 years depending on how they were installed. Shingles should not be installed on flat roofs (they need to be on an angle).
Something labeled a "50 year shingle" will likely not last more than 30 years.
Replacing a roof can take as short as 3 days and can cost around $9,000 (the materials are fairly inexpensive).
A lot of this will depend on location. For example, if you are in a sunny place, this will hasten the damage to the roof - put in a big tree! :)
Additionally, exterior roofs should be painted light to reflect the sun. White is the best! The difference between gray and block is not huge, the difference between white and gray is huge. The roof will last longer with white (if the roof expands and contracts with heat - this happens every day with the sun - will get damaged faster). Your house will also be cooler inside on a sunny day if you have a white roof.
Mold
Mold can be dangerous or not dangerous and it depends very heavily on your own immune system. Most people are fine around a wide range of molds. Some people are sensitive to specific molds, have allergies, or have weaker immune systems. We shouldn't have excessive mold in houses and the key culprit is excessive humidity. If a house or a part of a house has >90% moisture/humidity, it can cause mold. Most often water comes from crawlspaces. If it looks like water stands under a house, you will have problems with mold and mildew. If you are sensitive, make sure to wear a respirator in a crawlspace.
What to do?
- Lay plastic on the ground (easiest and cheapest). Ground can stay wet, but the water and moisture doesn't come up into the rest of the house. Mold & water may grow under the plastic, but that's fine as that means that it's not going to the rest of the house. Use very thick plastic (20mil) so that it stays over time. Knock it down with a mallet every two feet. Connect sheets with thick nails. This is a type of vapor barrier.
- Increase ventilation in a crawlspace. Only downside to this is that it may make your ground cooler, but if you have
- For significant amounts of standing water, trench around the house (this is much more expensive but may be necessary for serious problems). The bottom of the trench should slope from behind the house, down preferably both sides, to the street in front. This can be called a sub-surface drainage system.
What are sources of carbon monoxide?
Wood fires (must be vented properly), charcoal (do not burn charcoal inside!), gas appliances not functioning correctly (furnace, stove, water heater).
Make sure your gas flues are in good working order. Gas flues take gas away from your gas appliances and move them outside. If the gas flue is not properly ventilating or letting gasses into the house, this is very dangerous.
What is the single thing that you can do to help a house stay intact for a long time?
If you keep a roof on a house and keep it painted & sealed, a roof will make the biggest difference in the house staying intact for a long time! Most damaged houses are damaged because the roof was not adequately maintained.
What is the biggest threat to house construction?
Cheapness. An acceptable solution that will help your house last for a long time may be a little bit more expensive than the cheapest solution, but many people opt for the cheapest solution.
The 70s were the "era of cheapness" so it may be helpful to pay special attention to houses from the 70s.
What should I do if I want to learn the basics of home repair and home construction?
Diablo Valley College and other local colleges have construction courses. ASHI offers courses (possibly available online). Lots of book series: Readers Digest Home Repair is a surprisingly good book.
