Why are there side altars?

Q: Why do some churches have side altars? Why do the side altars often have tabernacles? –Angela

As usual, if you guessed “the way things were before Vatican II,” you’re on the right track.

Art and Liturgy - Saint Bridget Church Omaha.jpg
St. Bridget Church in south Omaha, Nebraska, with side altars visible in background

The Second Vatican Council, commonly called Vatican II by us Papists, took place from 1962-1965 and, among many other things, promoted a variety of cosmetic changes to the Sacred Liturgy. I say “cosmetic” because we ought to be clear that the Holy Mass offered today, in 2016, is the same sacrifice offered by Christ in the upper room on Holy Thursday, and at Calvary on Good Friday, and in Rome in 1959, and every other Mass ever. If this seems confusing to you, don’t feel bad, nobody else really gets it either. It is the core mystery of the Catholic faith. Anyway, back to Vatican II. Among the many effects of this council, one change is relevant to us today: priests were newly allowed to concelebrate the Mass.

Art and Liturgy - Pope John XXIII
Pope John XXIII, who convened Vatican II

Concelebration is when two or more priests stand together and celebrate the same Mass at the same altar. It is a fairly common thing these days, but prior to Vatican II, it was far less common and hardly ever permitted. One charming exception to this was at ordination Masses, where the newly-ordained priests were permitted to concelebrate with their bishop. In spite of this restriction, clergy were (and still are) required  strongly encouraged to celebrate Mass every day. Side altars allowed priests to celebrate Mass privately, on their own — remember that the “old Mass” was chiefly inaudible prayers said by the priest  — even at the same time as another Mass was taking place elsewhere in the church.

Could a church have been constructed with only a single “high altar,” and all the parish priests taken turns saying their Mass one after the other? Yes, but in general it seems it was more practical to construct a side altar, thereby allowing for some flexibility for the clergy. You can imagine how this sort of thing would go in a religious community or abbey with dozens of priests in residence.

Art and Liturgy - Shrine of Saint Stanislaus Cleveland Ohio
High altar and side altars at the Shrine of St. Stanislaus in Cleveland, Ohio

Although less commonly used today, these altars and tabernacles are still usable in theory, but in my experience many seem to be in need of refurbishment. Sometimes a side altar is used for an “altar of repose,” where the Blessed Sacrament is kept from Holy Thursday until the Easter Vigil, when the altar is stripped and the main tabernacle is barren.

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* I was incorrect about the requirement of a priest to say Mass daily. The post has been amended. Thanks to commenter Alex for the correction.

Header image by Serge Melki from Indianapolis, USA – Basilica of the Immaculate Conception – Our Lady of Lebanon Chapel, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=24320763

Pope John XXIII image by Gedoughty02 – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=45010500

St. Stanislaus photo by Owen M. DabekOwn work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=31476940


  1. The only required Mass for a presbyter without an office (pastors incur more obligations, such as the ‘Pro Populo’ Mass) is to concelebrate the Eucharistic prayer at one’s own ordination. Frequent celebration is a moral exhortation, not a requirement. See Canon 904: “Priests are to celebrate frequently; indeed, daily celebration is recommended earnestly.” The wording and conjugation of the Latin make clear that it is purely exhortatory, not mandatory.

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