March retail sales registered their biggest monthly gain in a year and easily surpassed analysts' estimates, helped by a surge in building material and garden equipment sales. Total retail sales increased 1.8% from February to $333 billion on a seasonally-adjusted basis, well ahead of analysts' estimates for a 0.7% rise, the Department of Commerce said. The results jumped 8.2% on a year-over-year basis. Core retail sales, which exclude automobile and parts sales, rose 1.7% in March to $255 billion vs. the consensus for a 0.6% increase. The Department of Commerce said sales of building materials and garden equipment and supplies were up 20.8% from March 2003, and sales of food services and drinking places rose 11.1% from the prior year. February's revised figures were revised up as follows: Total retail sales increased 1%, from a prior reading of a 0.6% rise, while core retail sales increased 0.6%, from a previous reading of unchanged from January.