House building activity weakened again in September, the latest Ulster Bank Construction Purchasing Managers' index shows.

The Construction Purchasing Managers' Index, which is designed to track changes in total construction activity, stood at 56.2 in September, down from 58.3 in August.

Any figure over 50 signals growth in the sector and activity has risen continuously on a monthly basis since September 2013, with the latest expansion the weakest in almost a year.

Ulster Bank noted that while construction activity rose at a weaker pace than in August, the rate of expansion in new orders accelerated. 

Companies also continued to increase their purchasing activity and staffing levels last month.

Ulster Bank said the strongest increase in activity across the three broad categories monitored by the index was on commercial projects, the first time this has been the case since June. 

Commercial activity rose sharply, and at a faster pace than in August. 

The rate of growth in activity on housing projects remained marked, but slowed for the second month in a row, while civil engineering activity decreased modestly to mark its first fall in three months.

Simon Barry, chief economist Ulster Bank, said that encouragingly, survey respondents said that improving customer demand supported another strong, and faster, increase in incoming new business flows. 

"In turn, robust activity and new orders patterns continue to underpin strong demand for construction workers, with the pace of job creation remaining steady in September at very healthy rates," Simon Barry said,

He noted that while sentiment among firms about the sector's prospects over the coming year moderated slightly in September, it remains at elevated levels. 

"55% of respondents anticipate higher output levels over the year ahead, with expectations of improved market conditions and higher new orders cited as important sources of support," the economist added.