In terms of non-religion time used to prepare pupils, teachers said it ran from an additional 30 minutes a week up to nine additional hours a week.
Overall, more than 70% of the 363 teachers surveyed said preparations for the sacraments takes more time than that officially available for religion.
In addition to the extra hours within school time, teachers also said anything from 30 minutes to 10 hours were given over to sacramental preparation outside of regular school hours.
While 90% of teachers work in a denominational school, just under half of those surveyed said they teach religion willingly. A similar survey carried out 10 years ago showed almost two thirds of teachers then taught religion willingly.
About 20% of those surveyed said they were not opposed to teaching religion, compared with the comparable figure of 12% a decade ago.
The survey also showed that almost two thirds of teachers back religion being taught during school hours, and a rise to 10% in the number of respondents who would prefer to teach a broad religious education programme rather than teaching a denominational religious education programme.
The survey also shows that more students within a particular school are not of the faith of the school, and that some schools do not have facilities to cater for students who do not wish to have religious education, while 85% of survey respondents said they believed the practicing of religion within families had fallen.