Most San Franciscans know about the city’s most deadly earthquake. But what about the Victorian homes that withstood those seismic waves, blazing fires and a century of subsequent wear and tear?
This image of a sagging Pacific Heights Victorian, courtesy of OpenSF History, conveys the magnitude of damage that the 1906 quake wrought on SF’s infrastructure.
It was an early April morning when light tremors and shaking roused city residents—a common occurrence for a city on a faultline.
But minutes later, a 7.9-magnitude earthquake struck just offshore, sending much more violent seismic waves throughout the city. The quake lasted for less than a minute, but the aftershocks were powerful enough to be felt in neighboring states.
The quake damaged the city’s buildings and immediately sparked dozens of fires around the city, many of which burned for days and completely decimated hundreds of city blocks. Historians say more than half of the city’s 400,000 residents became homeless, and Purge-style violence broke out as residents burglarized wrecked stores and deserted homes.
While the 1906 Earthquake was first and foremost a human tragedy—historians estimate up to 3,000 people died—the combination of foundation-shaking shocks and days-long blazing fires resulted in the destruction of 28,000 buildings in San Francisco.
Many of those destroyed buildings were SF’s iconic wooden Victorian homes, like the sagging Scott Street house shown in this photo. Though this leaning Victorian no longer exists, the building to the right still stands on 1610 Scott Street today.
Why Some Victorians Survived—And Some Didn’t
There has been no shortage of stories chronicling the preservation, restoration and sales of the city’s most historic homes. But how did the city’s remaining Victorians adapt to geologic challenges? Why did some turn into SF’s very own leaning-tower spectacles? And why are some Victorians sitting on plots of land different from where they were first constructed?
There are three reasons: sediment, foundation and mobility.
Sediment
One 1906 seismologist reported that areas with high sediment—usually parts of the city with ground reclaimed from the Bay—felt the quake’s shocks more intensely than others, sustaining greater damage to buildings and their foundations. The 1989 Loma Prieta Earthquake again brought this reality to light in the Marina, a neighborhood built on landfill where homes tipped and gas mains cracked.
In other words, the ground beneath homes built on sand dunes and landfill atop former wetlands can liquify during a big earthquake—making for massive, quake-induced destruction. Even after the 1906 earthquake and fires subsided, the ground’s lack of fortification in many areas led to sinking Victorians and leaning homes that look much like the unfortunate plot in this photo.
Indeed, this building looks like San Francisco’s version of the Leaning Tower of Pisa—though the similarities don’t stop at their leaning facades. Pisa’s lean is caused by soft ground that cannot support the structure’s full weight, much like many parts of historic and modern San Francisco. Early city developers turned the Bay’s wetlands into sediment-filled valleys in the eastern side of the city, and the Presidio sits atop a thousands-year old sandy deposit called the Colma Formation.
Though this 1612 Scott Street Victorian rested atop neither of those locations, homes most affected by the 1906 quake tended to be located in areas with more unstable geologic conditions—those which essentially turned into liquid when shaken by a quake.
Foundation
The foundations of numerous Victorian homes took an obvious hit after a century filled with earthquakes and tremors. While many city residents sought refuge in emergency “earthquake shacks” constructed in city parks, city planners knew that surviving homes needed refortification in order to survive the aftermath of 1906—especially when some tilted well past Pisa’s 5.5 degree lean.
SF residents started building Victorians in the 1850s, but their homes tended to lack certain modern innovations, both architectural and aesthetic: most Victorians lacked garages, many were constructed from redwood but built on brick foundations, many were “soft-story structures” that sat atop commercial buildings, and most lacked the kind of seismic retrofitting required of new buildings today.
As a result, residents who lived through the 1906 quake captured dozens of images of Victorians that slipped right off their brick and mortar foundations and sank into the ground.
For the Victorian homes that have survived to this day, most had to undergo seismic retrofitting that sounds as simple as it is pricey: Victorian homeowners can literally “tie the house together” by bracing walls and bolting down the wooden top part of the home to its foundation.
Mobility
If ground fortification or seismic retrofitting both fail, owners of Victorians had few other options than simply picking up and moving their homes.
In the immediate aftermath of the quake, many San Franciscans weren’t focused on the historical preservation of their Victorian homes. Before the 1960s, the rehabilitation and preservation of Victorian architecture was uncommon, resulting in the demolition of dozens of Victorians.
But some San Franciscans were deeply attached to their homes and chose to drag them right off the foundation, onto horse-drawn pulleys and into new neighborhoods.
Some Victorian homes were moved to accommodate new transit lines or rebuilding efforts in different neighborhoods in the city. When city officials began dissolving communities built around emergency earthquake shacks, some residents were hesitant to give up their new homes immediately. This resulted in dozens of earthquake-shacks-on-wheels, lumbering down SF’s streets at a pace no faster than one mile per hour.
Moving homes to new foundations and new neighborhoods continues to this day, though the justifications have somewhat shifted in recent years: where early 1900s movement efforts often came as a result of reconstruction and earthquake-related needs, some more recent home movement projects—such as the relocation of the Fillmore District’s Victorian homes in the 1960s—reflected city critics’ desire to gentrify neighborhoods that predominantly housed low-income families of color.
While San Francisco restores its existing Victorians and trundles old houses into new neighborhoods, the tectonic plates beneath are just as likely to keep shifting and moving. There is a 72% likelihood that a magnitude 6.7 earthquake will strike SF within the next 30 years, according to the U.S. Geological Survey, and smaller quakes have had ripple effects on the Bay Area's transportation lines.
But with enough foundation fortification and seismic retrofitting, San Francisco might just be able to avoid a future filled with leaning Victorians and sinking homes.