OAKLAND -- A hot real estate market in the past year helped push Alameda County's annual property tax assessment roll by 6.5 percent to $218.6 billion, according to a report Monday by Alameda County Assessor Ron Thomsen.

Of the $13.9 billion added to the county tax rolls, $5.2 billion came from real estate sales and transfers and $1.2 billion from new construction activity.

Oakland and Fremont, as the biggest cities, continue to have the largest assessed values ($47.7 and $38.7 billion, respectively), but fast-growing Dublin recorded the largest increase -- 15 percent more than the prior year.

Assessed values jumped by 9 percent in Contra Costa County during the same time and by 6.8 percent in Santa Clara County.