EARTHQUAKE RETROFITTING SCIENCE
The Nuts and Bolts - Installed with Care
Our company has a unique set of qualifications, including being led by a licensed professional engineer, that make our retrofits unmatched in detail and quality.
A seismic retrofit is the process where a home or building is upgraded structurally to better withstand the seismic forces it might experience from an earthquake. Reinforcement and additional connections are made at weak points so that the building is tied together and anchored to the foundation.
Common failure modes for residential homes are: the home sliding off the foundation and basement walls (also called cripple walls or pony walls) collapsing. To improve upon these weaknesses, anchors bolts are added and shear walls are installed. Anchor bolts prevent the home from sliding on the foundation while shear walls carry the load of the upper story and safety transmit it to the foundation. To create a shear wall we reinforce the existing studs between the foundation and the floor joists above with sheathing and add framing angle brackets.
The details such as location of hardware, how many, and what type are prescribed by engineering calculations to ensure they meet the code.
For even more details, including this technical write up on retrofits, visit our Blog.
Seattle homes are more at risk than most people understand. We forget about the lurking risk of a large earthquake because we don't get reminded with tremors frequently. Did you know this region had a 9.0 earthquake in the year 1700? It will happen again, its just a matter of time! Some of us were around in 2001 and remember being shaken by the Nisqually Earthquake, a 6.8M quake. Each unit of magnitude on the Richter scale is 32x more powerful than the last. That means a 9.0 quake would be over 1000x more powerful!
Compounding the risk is that most houses in Seattle are built before codes required seismic resistance. Houses built before 1980 have no anchor bolts and their shear capabilities are seriously inadequate.
Earthquake retrofitting is an easy and relatively low-cost way to protect your greatest assets. You can't put a price on life; the price to repair your home could be $100k+, if not a total loss. Repairing after a serious earthquake will be a nightmare because the demand for this service could leave you waiting for a very long time, all the while - you cant live in your house because it is unsafe.