House Bolting

House Bolting

House bolting, or foundation bolting, refers to the process of fastening a house to its concrete foundation to prevent the up-and-down, side-to-side motion of an earthquake from dislodging the house from its foundation.

Why You Need House Bolting

House bolts keep the base cripple wall from gliding away from the foundation. When the cripple wall, which is usually placed over the mudsill -- the wooden structure between the concrete foundation and the house, slides away from the foundation, the house can sustain severe damages in parts such as gas lines, living areas, electrical wiring, etc.

The bolts are used in combination with structures of plywood and shear transfer ties.

House bolting services are essential for homeowners all over the world as this is what ensures that the severity of any imminent damage is lessened. This post will shed light on some other house bolting techniques you should know about.

House Bolting and Seismic Retrofitting

Retrofitting a home is the process of reinforcing the home’s resistance to earthquake forces. Foundation bolts are only one component in a three-part seismic retrofit system. Foundation bolts are ineffective without the other two parts of the system, namely the plywood and the sheer transfer ties. These other two components provide a ‘load-path’ that channels the earthquake forces into the bolts, significantly minimizing the impact of the forces on the house.

There are a handful of retrofit foundation bolts, including epoxy bolts, expansion wedge anchors, Simpson Strong-Tie UFP IOs, etc. They all have been tested to prove their ability to hold the mudsill and the cripple wall to the foundation in the face of earthquake forces.

These bolts are typically placed with 5’ or less apart from each other in one story buildings, and 4’ or less apart in two-story buildings. The bolts come in different sizes with varying capacities; a 1/2-inch bolt can repel 1100 pounds of earthquake force, a 5/8-inch bolt 1500 ponds. These two sizes can be combined to take on earthquake forces of much greater magnitudes. In houses where the crawl space is too small to allow for direct bolting, side bolting is used instead.


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