Peabody-based Beacon Roofing Supply Inc. posted $27.9 million in net income for the fourth quarter, down from $31.3 million in the same period last year.

The company said in a statement that the lower net income was due primarily to a one-time income tax benefit of $5.1 million realized in 2011.

Fourth-quarter sales increased 3.9 percent to $598 million from $575.6 million in the same period last year.

Total sales for the full year increased 12.5 percent to $2 billion from $1.82 billion in 2011. Existing market sales increased 6.3 percent. In existing markets, residential and non-residential roofing product sales increased 11.8 percent and 2.3 percent respectively.

Annual net income was $75.6 million in 2012, compared with $59.2 million in 2011.

Paul Isabella, the company’s president and CEO, said in a statement: "We are very pleased with our record quarter and annual 2012 results, which exceeded our expectations. Our total sales benefited from the positive impact of acquisitions and from a 6 percent increase in existing market sales for the year."