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Why Your Home May Need a Seismic Retrofit

by | Sep 5, 2020 | Construction Tips, Home Maintenance, Uncategorized | 0 comments

The risk of an earthquake is just a part of life when you live in California. If you are old enough, you have probably lived through a few. You may have seen firsthand the power and destructive force of these events.

Owning a home in California means that you need to be prepared for earthquakes. Beyond having the necessary emergency supplies on hand, you have to consider whether your home is built to withstand a major earthquake.

Newer homes are built with a better understanding of the way earthquake forces act on a structure, but older homes may be at significant risk. These risks can cover everything from severe property damage to issues that could put the lives of occupants at risk.

If you do live in an area that is at high risk for earthquakes, you need to consider that your home might need a seismic retrofit. With seismic retrofitting, you upgrade and reinforce the structure so it can withstand the forces of an earthquake.

In this post, we are going to look at some of the issues that can be addressed with a seismic retrofit.

Pony Wall Collapse

Pony walls, also known as cripple walls, are short walls that run between the home and its foundation. The home is built on these walls and they support the weight of the entire structure. In the event of an earthquake, the lateral forces can cause these short walls to collapse.

To prevent collapse, a seismic retrofit would involve bracing the pony walls. This is usually done by reinforcing the pony walls with plywood. It is important to recognize that you need plywood that is strong enough and thick enough to provide adequate bracing. You also need to consider the type of nails used for the project, the spacing of the nails and connecting the plywood panels.

Foundation Bolting

Many homes are not adequately fixed to their foundations. When an earthquake occurs, this can cause the house to displace from the foundation. This type of damage can be very expensive to repair, so it is better to make sure the home is properly anchored to the foundation.

For this type of seismic retrofit, you would need to have large anchor bolts installed to hold the home on the foundation. To do this job, a seismic retrofit contractor would drill holes through the sill to connect the anchors to the concrete foundation. If there isn’t enough room to drill, they might install steel plates to hold the structure in place.

Soft Story Collapse

A soft story is a room or area of a home that is built over top of a space that is open and lacking support. A common example is if you have a garage or parking area with a room built over it. If the home is subject to a significant earthquake, the floor above the open area could collapse.

A soft story can be reinforced, but the exact solution will depend on the structure. Common solutions include using plywood sheathing to increase shear strength or adding steel framing for additional support.

Chimney Collapse

Chimney collapse is one of the most common types of earthquake damage. During an earthquake, a chimney can collapse and this will send brings falling into or around the house. These bricks can cause damage to other parts of the home or injury to the occupants.

The correct fix to prevent chimney collapse will depend on several factors. In some cases, it might need to be removed or filled with concrete. You might be able to prevent collapse by shortening the chimney or by installing plywood to reinforce the roof around the chimney. There are also different techniques for bracing chimneys to prevent collapse.

If your home needs a seismic retrofit, it is not something you want to put off. An earthquake can happen at any time and the damage can be severe. It might cost a little right not to perform a seismic retrofit, but it is an investment in protecting your home and the people who live there.


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I Construction & Structural Inc
69 Paul Drive
San Rafael CA 94903

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