I’m always hearing that the ceremony lasts for an hour and couples plan their day around this. From experience, the ceremony lasts a lot longer than an hour!
If you are having the full church service with music you are looking at 1hr 20mins – 1hr 30 mins for the ceremony alone. Then take into account that the bride is usually late for an Irish wedding – add another 15 minutes for that (at least!). Then you’ll have the greeting the guests at the back of the church – another ten minutes or so. If the weather is bad, the photographer might also bring you back into the church for some family/bridal party photographs so that can add another 20 mins to half an hour. Worth taking into account when planning your times for the various parts of the day – and always add a bit extra for the unforeseen bits and pieces like the car forgetting to go back to collect the bride or arriving at the church having left the flowers back at the house or the priest leaving for his lunch as he got the time wrong!