From the Superannuation Handbook and Guidance Notes Established Civil Service Scheme, those employed on or after 6th of April 1995 pay the following contributions:
(a) 1.5% of gross remuneration (i.e. basic salary plus any pensionable allowances)
(b) 3.5% of net remuneration (i.e. gross remuneration – as indicated at (a) above – less twice the annual rate of the maximum Contributory State Pension (CSP) currently payable by the Department of Social and Family Affairs to a single person without dependants).
The current rate of CSP (correct as of 22/11/2012) is €230.30 a week.
If you have a spouse and/or child, there is an additional 1.5% contribution.
More details are available on the Irish Civil Service Pensions Information Centre.