The latest National Construction Index shows that planning applications were down 19% in the first half of 2012 compared to the same time last year.
The index is published by consultants Link2Plans.
But three counties - Donegal, Sligo and Leitrim - recorded marginal increases in the number of planning applications.
The index tracks activity in the residential sector - north and south of the border - based on commencement notices and planning applications.
Commencement notices are the paperwork builders file prior to the start of building as distinct from planning applications which can lay dormant for years.
Commencement notices fell by 7% from the last index, but three counties - Westmeath, Cork and Cavan - saw increases.
Link2Plans said that despite the slowdown in applications, a total of 10,287 individual residential projects applied for planning permission in the first six months of the year.
However, the survey noted dramatic regional variations in construction activity. It said that the counties of Cavan, Donegal and Monaghan combined have three times more construction activity - per head of population - than Dublin.
It also noted that Munster, Connacht and Northern Ireland had about twice the activity per head of population than Dublin.
''There is still a huge number of housing construction projects taking place, albeit those projects are on average smaller than in previous years,'' commented Link2Plans's managing director Danny O'Shea.
