In most seismic zones like California, earthquakes are a major concern. With experts predicting an increase in magnitude with every passing year, is your home ready? The best and only advisable way to answer this question is to consult a structural engineering firm or more specifically, a structural engineer to assess your home’s earthquake-resistant ability.
However, if you’re feeling very self-sufficient, you can research on buildings that fail and those that survive during an earthquake and compare them to yours. Better still, you could learn about what keeps a structure from falling during an earthquake and get the same help for your home.
This article features 10 ways to prevent earthquake damage and common building weaknesses you must take note of.
1. Anchor Your Home to Its Foundation
Anchoring your home to its foundation will, to some extent, prevent your home from sliding off during an earthquake. So many types of damages can occur during an earthquake, sliding off of a building from its foundation is one of them. And it could be very disastrous.
If your house has an elevated floor base, normally the joists on its lowest floor will be supported by a weak wall or rest directly on the sill plate. To determine if the frame of your house is attached to the base, go to the crawl space and look for the heads of the anchor bolts installed along with the sill plate. If the house is built on a slab base, it will not have spaces to crawl, but an unfinished garage should give visual access to the anchor bolts.
If you do not find any anchor traces, you must drill holes through the sill plate and the concrete to install them. If there is not enough space to drill, steel plates or makeup baseplates should be used to secure the sill to the concrete.
2. Brace the Cripple Wall
A crawl space in a building might contain a cripple wall. The weight of the whole building rests on these walls, therefore, to resist earthquake loads, reinforcement of these walls is imperative. Cripple walls without reinforcement can bend during earthquakes, causing displacement or collapse of the upper structure. Failures of this nature are a common cause of damage caused by the earthquake.
One way to identify a braced cripple wall is by looking out for plywood or diagonal sheathing nailed to the uprights, which forces them to shear the walls by definition. Therefore, if you don’t see this in your cripple walls, you need to rectify the situation as soon as possible. Contact a structural engineer, he/she will take into account all the variables to design a solid and economical reinforcement system for your cripple walls.
3. Retrofit the Soft Story
Soft stories could sometimes have aesthetic features, however, in seismic regions it could result in structural damages in the event of an earthquake. If there are open spaces (like a large garage below a building) in your home, there is a soft-story in your building.
The walls of a soft story are more often than not exposed to earthquake damage, this is because the weight above the space weakens its walls.
Retrofitting soft stories depends on the configuration of the building. Some retrofitting options include;
- Reinforcing the walls with plywood panels
- Reinforcing the walls with steel belts
- Reinforcing the walls with hold-down anchors
- Adding a narrow shear wall, this will reduce the size of the opening.
However, a steel moment frame may appear to be the only right choice.
If there is such a condition in your home, you should consult a structural engineer to find an appropriate reinforcement solution.
4. Homes on Hill or Hillside? Call an engineer
Studies show that houses on the hillside suffered enormous damage during earthquakes. Those supported by concrete columns and platforms, called stilt homes, are particularly vulnerable. During the seismic activity, its reinforcement in diagonal tension stretches and weakens, allowing seismic forces to separate the house from its foundations.
In a nutshell, if this is your situation, consult a structural engineer to assess for possible reinforcements.
5. Replacement of unreinforced masonry foundations
Most ancient buildings have foundations of bricks or stones. And, unlike recent concrete foundations are not often rebar or concrete reinforced. One might ask, why must it be reinforced? Well, an unreinforced masonry can only do so much when resisting earthquake loads, it has low stiffness and could result in the foundation sliding off.
Replacing your unreinforced masonry foundation with concrete and rebar will help minimize earthquake damages. If your base is stone or brick, make sure to consult a structural engineering firm to assess it.
6. Reinforce masonry walls and chimneys
Research shows that chimneys and unreinforced masonry walls are susceptible to structural damages during an earthquake.
To mitigate these seismic damages, brace your masonry walls and chimneys with the following;
- Steel rods
- Concrete blocks
To determine if your home has this weakness, it is best to find the plans for your home and deliver them to a structural engineer.
It is best to lean to your engineer for the best solutions that match your building’s needs.
7. Install Shear walls
The studs in your home resist vertical loads by transferring it downwards to the foundation. Without reinforcement, however, they cannot withstand the horizontal loads of an earthquake. Bracing the studs involves attaching a sheathing board, which assembly then results in a shear wall.
Old houses built under a less strict seismic code (or nothing) may not have adequate reinforcement in their design. The lack of reinforcements exposes homes to earthquake damages. Its walls may deform, resulting in significant damage or collapse.
Unlike many seismic reconstruction measures, adding shear walls is not expected to generate significant costs. The retrofitting can be done by exposing the plywood frame and panels to nail them to the studs that your engineer deems appropriate.
8. Make sure your design is earthquake resistant
The design of a building plays a major role in its earthquake resisting ability. Designing too large windows, overhang, or irregularly shaped walls, can increase the seismic vulnerability of your home. During an earthquake, its glass can break and complicate its evacuation efforts. Overhangs without proper reinforcement can break away from the house and collapse.
9. Brace your water heater
During an earthquake, an unbraced water heater can prove very costly. It can collapse, breaking the gas and water pipes, which can result in fires and floods. With adequate reinforcement, one can avoid all these calamities.
Firstly, you need to know the condition of your water heater. If the unit is not braced, attach it to the frame of your house and bolt straps to the studs. If you do not see evidence of such reinforcement, your water heater may collapse during seismic activity.
10. Fire prevention plan
When the ground shakes, the gas pipes can burst, causing leaks which could lead to fires and explosions. While you can’t avoid earthquakes, you can do your part to prevent them from causing fires. Be sure to use flexible hoses to connect natural gas to your appliances and know when to close the gas supply to your home.