Donald Ray Williams, 51, of East Palo Alto, was convicted of arson for the fire at 310 University Ave. on July 1, 2007.
His conviction was in 2009, but the trial and sentencing were delayed because of court-ordered hearings about his mental competency and then periods of mental health treatment, according to the U.S. Attorney's Office.
Williams allegedly climbed up a pipe on the outside of a building, which housed a Walgreens and a Subway sandwich shop on the ground floor. He broke into an empty office on the second floor, where he lit newspapers on fire next to a wooden bookcase, and the flames spread throughout the building, prosecutors said.
No one was hurt in the fire, but flames caused a roof to collapse, nearly injuring firefighters who had just moved out of that area, according to prosecutors. The blaze caused an estimated $28.6 million in damage.
Williams was identified as the arsonist with the help of security footage that showed him removing his shirt and climbing up the building. The shirt was found in a nearby garbage bin with Williams' DNA on it, according to the U.S. Attorney's Office.
Along with the 20-year sentence, he was ordered by U.S. District Court Judge Jeremy Fogel to serve three years' supervised release upon leaving prison and to pay $28.6 million in restitution, prosecutors said.