Best day to visit Sagrada Familia?

Go Monday - avoid the weekend altogether. With timed visits, it's a constant stream and the crowd is therefore never unbearable.

I would also suggest going as early in the day as possible. And pre purchase your tickets to avoid the extremely long lines. We had timed ticket for 9 or 9:30 and it was great. Walked right up to front of very long line and walked right in. There were very few people in the church for the first 30-40 minutes. It was great before the crowds.. By the time we left, it was becoming quite crowded.

Thank you Brisbane and Kathryn for the tips. Yes, I have heard that the 9:00 a.m. slot is best, just a matter of us being up and ready to go after staying up late in Barcelona! Mon. sounds good, but I was thinking about Montserrat on that day?

Go with whatever fits in as long as you go early as Kathryn suggests

We visited SF on a Sunday last month and it was not a problem. We booked our admission, guided tour and tower tickets directly on the SF website about one month in advance. Our time slot was approximately 9:30 am to 11:30 am.

This is a church, but the SF gets almost all of its revenue from tourism. IMO, if the SF gives you a time slot, I doubt that your visit will conflict with any religious ceremonies. In fact, if there was a Mass during your visit, it may actually make your visit more interesting. I found that the SF was very efficient in keeping the streams of people moving.

I have tickets on Sunday and will attend mass prior to my visit. When I contacted SF they emailed to advise times and that the masses are in a "specific" entrance. Never having been there prior..it sounds like a separate section altogether. I don't think the main church is used for services but on special occasions.

If you have Netflix, check out the "Sagrada" documentary and you can see how much has been constructed from about 5 years ago.. It is interesting to learn that the classic looking Gaudi-inspired sculptures are all being carried out by a Japanese immigrant who converted to Catholicism and the modernistic Passion facade sculptures were done by a Spaniard who had rejected religion or at least has become agnostic.

One somewhat cynical commentator described the SF as being like Disneyland. In some respects, he is correct. I found that the whole experience from the website ticket purchase, admission, guided tour and the elevator up the tower to be extemely efficient. There are lots of window openings in the tower to give the streams of tourists plenty of air and picture taking opportunities. Our Sunday visit was very crowded, but it was a very pleasant experience. Everything of interest was above you (except for the turtle and tortoise), so the crowd below does not interfere with your view. The SF certainly makes it easy for tourists to spend money and enjoy their visit.

Thank you everyone for the advice. I'm going to book a 9:00 a.m. ticket for SF. So the tower is worth it? Which one?

The towers are worth the extra cost. Remember that every Euro you spend helps the construction of the SF. I had read that both had excellent views. I think Passion is slightly higher. We chose Nativity because there is a small bridge you cross at the top to step outside for a view. An elevator takes you to the top, you cross over and then walk down. It is pretty easy compared to climbing the Cupola or the bell tower in Florence.