It is not a true fan vault in its construction but is made up of a series of stepped and cantilevered blocks cut on the underside to form the appearance of vaulting.
Although the Gothic vault, and to a large extent the fan vault, uses a stone vocabulary, the use of timber like that of the stalls at Gloucester reflects a more intimate scale and delicacy of construction.
Trinity Chapel is regarded as the first structural fan vault to be made of jointed masonry following the conoid form.
Because the cloister construction has to span between other existing structures and external buttresses around the cloister, the conoid pocket - that is the space behind the masonry shell - is left open to the void between the fan vault masonry and the lean-to roof above.
Unlike the Gothic vault, where the expression of forces is described by ribs and spandrels, the blocks of the fan vault conoid are free to be carved to the reticulated design of the enclosure.
Due to the circumstances in which the fan vault evolved it is often seen as an adaption or as an addition to the church, either as a side chapel or a porch, uncertain as to whether it is an ostentatious addition or part of a quiet, well-crafted country churchyard.
Instead of razing the churches completed after the Norman Conquest and rebuilding in the Gothic, they modified and added to these existing structures to create fan vaults as a decorative layer within.