There is no honest single average: San Francisco sidewalks are priced per square, and what is under the squares sets the price. Tree roots and curb work add cost. Root damage from a street tree may be the city's bill, and cold patch will not close a Notice to Repair. Tip: photograph the notice and every marked square, and ask for a written price for that list. San Francisco Concrete Contractors, (415) 687-3728.