The British construction-sector activity index in April fell to 53.4 from 53.8 in March, according to a survey from the Chartered Institute of Purchasing and Supply.
The April reading is the lowest since December 2001 and is the second fall in a row.
A reading above 50 signals expansion and below it, contraction. The greater the divergence, the more rapid the rate of change.
Although the rate of growth of overall activity eased marginally, new orders in April was the fastest since December 2002. In April, the seasonally adjusted new orders index came in at 58.7, up from 56.3 in March.
Mr Roy Ayliffe of the Chartered Institute of Purchasing and Supply said: "April saw the construction sector experience the slowest growth so far this year, yet the sharp increase in incoming new orders is encouraging".