St Andrew's is of considerable significance, both for its architecture and as an institution. The aisleless nave and axial eastern tower, both with long-and-short quoins, are of equal width and are part of the same late 11th-early 12thc. build. The present rectangular chancel is Perpendicular Gothic. The foundations of the former chancel, exposed in the 19thc., revealed this to have been apsidal in plan. There is Romanesque architectural sculpture on both the interior and exterior of the nave, the blocked W doorway and the tower arches. A small group of Romanesque carved fragments is stored in the porch and inside the church.

Great Dunham is situated in the Hundred of Launditch. It was an outlying estate of the important royal manor of Mileham, formerly in the hands of Stigand, Saxon bishop of Elmham (East Anglia) (1043) and Archbishop of Canterbury (1052), but at the time of DS held for the king by the Norman, William de Noyers. DS records that Reynold the priest had holdings in Dunham, with the daughter of the landholder, Payne. St Andrew's church was among the possessions of nearby Castle Acre Priory. A charter of 1138-45 issued by bishop Everard of Norwich refers to the chapel of St Mary belonging to St Andrew's.

The date of St Andrew's is still a matter of debate. Pevsner describes it as an 'Anglo-Saxon' church of the late 11th/early 12thc. overlap. Malcolm Thurlby places it in the early 12thc, comparing the blank arcading in the nave with that in the presbytery tribune gallery of Norwich Cathedral (begun 1096). Consistency in the treatment of architectural sculpture throughout the building, on the tower arch, nave blank arcading and W doorway (e.g. the stepped detailing of the imposts in all three locations), certainly indicates that the surviving Romanesque church is a homogeneous structure. The documented chapel of St Mary, associated with St Andrew's was still standing in 1522. It suggests that St Andrew's should be seen as a mother church of some kind, exemplifying an ancient hierarchical system of pastoral care largely superseded by 12thc. As such, in its late 11th/12thc. incarnation, St Andrew's stands towards the end of a long tradition, in institutional terms. The combination of pre-Conquest features such as long-and short quoins, with Romanesque details like the billet-type ornament on the W wall, suggests that the church can be seen as transitional in an architectural sense as well. Fragment C, the colonnette, is very similar to one recorded at Great Dunham Old Rectory. Several examples of Fragment F, the voussoir with a decorated soffit, can be found, among many other Romanesque carved stones, reused at nearby Rookery Farm, and another example is also preserved at Castle Acre Priory, 3 miles to the W. Decorated at both ends, front and back, these distinctive voussoirs clearly came from a free-standing structure. Assuming that the arcade they formed rested on chamfered imposts, this structure would have been supported on capitals with a top surface that was about 0.30 m square, the likely dimension of, for example, a single cloister capital. It has been suggested that the reused Romanesque masonry at Rookery Farm came from the lost chapel of St Mary, situated 50 yards W of St Andrew's. Alternatively, the elaborately decorated sculpture fragments at all three Great Dunham sites (St Andrew's, The Old Rectory and Rookery Farm) may have come originally from the dismantled priory buildings at Castle Acre.