I was planning our first morning on the Historic Paris Walk in Paris. I noticed that RS says there are weekday masses at Notre Dame at 8 & 9am, and we were planning to be there at 9. I'm sure I can't tour the church interior at that time, but can you slip in between services (they don't let folks tour during Mass do they)? That got me thinking, we want to visit quite a few churches, and while we've got one mass planned, I'd mainly like to just wander and enjoy the interiors. How do you know if a service is happening before you enter? Are the times posted, or is there a person on post at the door? I don't want to be embarressed walking in.
At Notre Dame, the daily mass is held up in the way front of the church and is closed off from the main part. We were there at 8:00 on a Thursday and had no idea there was mass going on - you couldn't see or hear it. You are welcome to come in and quietly look around the church during the mass. However, not ALL of Notre Dame is open until 9:30 I believe. If you speak French - check out this webpage.
http://www.notredamedeparis.fr/Horaires
At St. Sulpice, we also happened to show up during a service, but they had the south doors closed with a sign (in French). They also had a man standing there letting people in for the service. The door on the west side was open for visitors to tour the building. (Again, the service was in a separate area.)
However, at some places - Westminster Abbey, St. Pauls, they are not open during services for those who want to just wander around.
In Europe, many churches are great tourist sites. You are welcome to attend any religious service but only as a worshipper and not as a tourist. Depending on the church, many have staff at the door to screen those who wish to enter. Some even have a fee to enter and tour. Signs showing the times for religious services are usually posted at or near the entrance.
Most churches do indeed have their mass/service times posted on the door or a sign outside. If you know the churches you might be interested in viewing, Google them. That's how I found mass times for Saint-Sulpice and for some churches in Dublin.
When we were in Mexico, a bunch of tourists turned up in the middle of a mass! I can't tell you how pleased I was to see someone show them the exit. Honestly, check the times listed and try to avoid disrupting a mass. No tour could be that important.
This is in response to your question:
"(they don't let folks tour during Mass do they)?"
I really wish they would all stop allowing wandering tourists to peek/tour during mass/services. I just think it's rude to be honest.
You can only imagine how I must feel when I've witnessed tourists talking and wandering churches during mass.
Sadly, my scooper runneth over at times
We happened to enter Notre Dame right before a service in the late afternoon. We were allowed to sit and listen to the beautiful music and stay for as much or as little of the service as we wished. It was one of the most moving things we did while in Paris.. Notre Dame seemed to be big enough to accomodate the service - and the tourists and the tourists were quiet and respectful of the service.