Five San Francisco house extensions designed to contrast the original architecture

These five houses in San Francisco are traditional in the front and have contemporary extensions in the back.
The California city is known for its hilly terrain dotted with charming, historic houses, and a number have been enlarged with rear extensions that contrast the home's original architectural style.
Read on for the examples of contrasting extensions:
Alamo Square Residence by Jensen Architects
This Victorian house was renovated and extended by local studio Jensen Architects. The addition