Eh, well that is what concerns me—the house is not new—guessing from 70s based on what I have seen.
Problem is that it is in the hills—terraced up the hills are house upon house with retaining walls.
He is there because lives there almost rent-free—and in the Bay area, that is an amazing thing to pull off.
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The safest housing in the Hayward area were built in the ‘20s and ‘30s.
They get lots of cracked plaster, but the building remains safe, and can be repaired at minimal cost.
The stuff built from ‘72 onward is way too rigid, and in a major quake will likely have the foundation destroyed because the frame of the building is rigid. (new and “improved”)