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House Bolting

Earthquake Retrofitting | House Bolting Installation in Los Angeles | Orange | Ventura

What Does House Bolting / Earthquake Retrofitting Means?

The term retrofitting refers to the modification of an existing structure (property) or device for the purpose of increased safety, efficiency or energy conservation. Retrofitting a home is a process that ties a home together. It increases the resistance to earthquake damage and the risk of injury. In short, it significantly strengthens your Southern California home in Los Angeles, Orange and Ventura Counties.

A safe home is one that can withstand earthquake shocking forces and is a home built on a firm foundation. By securely fastening the house to the foundation and securely connecting the house components together, the chances of withstanding the next earthquake and keeping you and your loved ones safe from harm are greatly improved.

Most residential homes are either built on slab or raised foundations. The home’s weight is the primary reason that keeps the house from moving or sliding off its foundation.

Bolting is the process of fastening the house to the foundation perimeter. Bolting your house is the best measure you can take to prevent damage inflicted by:

1. Earthquakes

2. Natural house settling

3. Water damage

Foundation Bolting / House Bolting:

If your house was built before 1950, it is indeed just sitting on your concrete foundation. IT IS NOT ATTACHED IN ANY WAY! This means that in even in a small tremor, your house can go sliding off into your driveway. The Mud Sill is the wood that rests directly on top of the foundation. Until the 1950's builders did not often bolt the mud sill to the foundation leaving it vulnerable to sliding as a result of earthquake movements.

Foundation bolting (house bolting or earthquake retrofit) has been compared to a seatbelt for your house. The up-and-down and side-to-side motion of an earthquake can shake an unbolted house off its foundation.
During the 1994 Northridge earthquake, thousands of unbolted homes were damaged or destroyed. Foundation bolting is easy, quick and inexpensive and provides greater protection against the forces of earthquakes.

Cripple Wall Bracing:

The cripple walls are the section of your house that rest right above the mud sill. They support the weight of the house and create a crawl space. If the cripple wall is covered on the exterior with only stucco or wood siding, it is not strong enough to resist earthquakes. You will need to strengthen your cripple wall to prevent serious damage to your home by bracing the cripple walls with plywood.

Unbraced cripple walls may collapse with the side to side swaying of the house during an earthquake, causing the house to fall. New lumber would be added as backing to create solid edges for the shear wall nailing, as well as expansion bolts placed and the framing anchors would connect the rim joist to the top of the cripple wall. The cripple walls are now braced.

Bracing the cripple walls by using structual-grade plywood is simple and provides greater resistance to earthquakes. Bolting your mud sill to the foundation and adding plywood to the cripple walls are the two most cost effective steps you can take to strengthen your home for earthquakes in Los Angeles, Orange and Ventura Counties.

On many homes it is not possible to install foundation bolts because there is too little room between the top of the mudsill and the floor of the house. This is because either there is no cripple wall or the cripple wall is extremely short. In these cases special hardware known as "foundation anchor plates" are used to secure the house to the foundation.

Wood Blocking:

In applications where the mudsill is wider than the cripple wall studs, blocking will need to be installed on top of the mudsill to provide a nailing surface for the sheathing. In order for sheathing to strengthen the cripple walls, it needs to be properly nailed on all four sides.


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