May 5 (Reuters) - SIG said on Wednesday it expects to deliver an underlying operating profit in the first half of 2021, and forecast higher annual profit than previously expected, as the building materials supplier recovers from a pandemic-led slump.

The company, which supplies roofing and insulation materials in Britain, France, Germany, and Ireland, among others, had said in January that it expected a return to profitability in the second half of 2021.

"After a solid start in January and February, sales volumes then picked up strongly, and March and April traded ahead of management's expectations," the company said in a statement.

British construction activity grew at its fastest pace since 2014 in March, boosted by a restart in postponed hospitality, leisure and office projects as restrictions related to the COVID-19 pandemic started to ease.

In March, SIG reported 2020 underlying operating loss of 53.3 million pounds ($74.06 million), compared with a profit of 42.5 million pounds a year earlier.

The supplier to residential, non-residential, and renovation maintenance improvement markets also said its performance in the year so far has been "ahead of expectations", with group sales jumping 29% from its corresponding four-month period last year. ($1 = 0.7197 pounds) (Reporting by Aby Jose Koilparambil in Bengaluru; editing by Uttaresh.V)