What is a Side Aisle?

A side aisle is a longitudinal space that runs parallel to the main nave (central aisle) of a church, basilica, or large hall. The side aisle is separated from the nave by a row of columns, piers, or pilasters that support the structure above. In classic church architecture, a church typically has two side aisles, one on each side of the central nave.

The side aisle is generally lower and narrower than the nave. This height difference is exploited for lighting purposes: through the clerestory (the row of windows above the side aisle arches), natural light enters the central nave. In Romanesque and Gothic churches, this is a defining characteristic of the spatial experience.

Structurally, the side aisles play an important role as buttresses for the lateral thrust of the vaults in the main nave. The roofs of the side aisles work in conjunction with flying buttresses (in Gothic architecture) to absorb horizontal forces.

Applications

The term side aisle is primarily relevant in the context of church construction, heritage conservation, and architectural history. When restoring or converting churches, monasteries, and other historic buildings, the side aisle is an essential part of the spatial organisation and structural logic.

Modern architects apply the principle of the side aisle to industrial and hall buildings, where lower side spaces flanking a tall central hall are used functionally for storage, plant rooms, or office accommodation.

Related Terms

• Nave
• Crossing
• Column
• Pier
• Vault

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