If the actual existence of an architecture specific to the Temple is doubtful, it is none the less true that it is permissible to perceive in the use of certain forms or dispositions a symbolic content related to the conception of the spirituality of the Templars. But in its outline and its order, this architecture is inspired by the monastic architecture of the time, especially Cistercian style and references.
Let us remember that every sacred building rests on an articulated set of formal and other symbols whose purpose is to put in permanent relation the sacred, but nevertheless terrestrial, built site with the divine world, the symbols serving to express this relationship materially.
Two types of sacred buildings were favored by the Temple: the church and chapel with rectangular or basilica plan, of early Christian origin, with the shape of a long square, generally oriented towards Jerusalem. The building has a nave, often with one and sometimes with three aisles. There is no break between the nave and the choir, which is closed by a semicircular dome with in the wall three narrow windows or triplet of Romanesque or Gothic style, according to time.
The back of the facade is often pierced by a single narrow window.
This simplicity is also found on the outside openwork facade of the simple portal, sometimes decorated with small columns, and a middle window on the first floor, which is topped with a bell-tower arcade. Often,this is replaced by a more traditional bell tower leaning against one of the side walls of the building. Both inside and outside, the decoration is discreet and uniform, though regional differences exist, and limited to foliage, some animal figures or hooks ("crochets") based on the Cistercian model.
First illustration and text (translated from French and slightly edited) from a blog on Templar symbolism on templiers.org.free.fr