The architecture of Hertfordshire buildings may be most conveniently discussed under three separate sections, namely:—(a) ecclesiastical, or buildings related to the church; (b) military, or castles; and (c) domestic, or dwelling houses and cottages.

As in England generally, the architecture of the older buildings of all three classes has been affected to a greater or less degree by the nature of the building materials most easily accessible. Throughout the northern chalk area of the county the Totternhoe stone of Bedfordshire and the northern flanks of Hertfordshire was largely employed in church building, both for inside and outside work, to the latter of which it is but ill suited. Flint—in the better class of work “faced” or “dressed” by fracture so as to present a flattened outer face—was also very extensively used. The Norman builders of the tower of St Albans found, however, a quarry ready to their hands in the adjacent walls of Verulam, and we accordingly find this part of the structure made almost entirely of the characteristic Roman bricks or tiles. Contemporaneous brick was also locally used to a very considerable extent even in the chalk districts; and in the north-western part of the county there are numerous beautiful examples of Tudor brick chimneys, as at Water End. Timber in the old days was, however, much cheaper than bricks, and we consequently find many of the older buildings—especially cottages—constructed of a framework of wood, arranged in the fashion of a net, with the large “meshes” filled in with brick. This type of work is locally known as brick and studding and to the architect as half-timbered work. Other buildings were largely constructed of a wooden framework overlain with lath-and-plaster work.

Many of the churches built of flint or Totternhoe stone have their angles or quoins made of harder material; in many instances of stone apparently from Northamptonshire, but in other cases of Roman brick; similar materials being also used in the arches of some of the churches.

A large number of Hertfordshire churches have relatively low battlemented towers, frequently with a short spire or steeple in the centre as at Tewin, or a turret in one corner. Kensworth is an example of such a battlemented tower without either spire or turret; St Mary’s, Hitchin, Tring, Northchurch, Barnet, Bushey, King’s Walden, Cheshunt, and Watford are examples of towers with a turret in one angle, while at Ashwell there are turrets in all four corners. Some of the smaller churches, like St Michael’s, St Albans, originally had no aisles. Clothall church is peculiar in that the roof of the tower forms a four-sided cone; while the roof of the church at Sarratt is equally unique in being saddle-backed, that is to say, having a ridge running at right angles to that of the roof of the nave and chancel.

Apparently there is no wholly Saxon church in the county, although several of the older ones were constructed on the site of Saxon buildings, many of which were probably of wood, and thus either perished through decay or were burnt during the Danish raids. On the other hand, there are remains of Saxon work in St Albans’ Abbey, and there are several Hertfordshire churches which are referred with a greater or less degree of certainty to the period before the Norman conquest; the original part of St Michael’s, in St Albans, and of St Stephen’s, to the south-west of that town, may be cited as examples, both dating from the middle of the tenth century. The church of Sandridge—on the road from St Albans to Wheathampstead—may likewise date from the same epoch.

Of Norman churches there are numerous examples, among which may be cited as a fine specimen St Mary’s, Hemel Hempstead, whose tall octagonal tower and spire are visible from a long distance. The Norman arches of the nave are of great solidity, while the western doorway, dating from about 1140, is a magnificent example of the work of the period. Sarratt church is also largely Norman, as was also the old church of St Nicholas, Harpenden, unfortunately pulled down (with the exception of the much later tower) nearly half a century ago. A considerable portion of St Albans’ Abbey (now cathedral), the pride of the whole county, is also Norman; the tower of Roman brick being, apart from modern additions, wholly of that period. The old Saxon Church of King Offa, which stood on or near the site of the present building, appears to have been completely swept away by Abbot Paul of Caen (1077–1093), the founder of the present abbey, which although completed by him, was not consecrated till 1115. “It is to be inferred,” according to the Victoria History of Hertfordshire, “that a clean sweep was made of the old buildings, and no evidence as to their site has been preserved. The Norman Abbot’s contempt for his Saxon predecessors ... led him to destroy their tombs, and he doubtless laid out his new building without attempting in any way to accommodate them to those previously existing on the site. But he preserved and used up in his new church some of the stonework of the old building, giving a very prominent place to the turned shafts which still remain in the transept, and are the most notable relics of the Saxon building.” In the present nave, which is the second longest in England, the first six pillars on the north side belong to the original structure of Abbot Paul; after which we come to Early English (Pointed) work; this being continued to the west end of the building and back to the fifth pillar on the south side, whence Decorated work extends to St Cuthbert’s screen. The Norman work (1077–1093) of one side thus faces Decorated work (1308–1326) on the other, but this is due to accident rather than design, the Norman pillars having given way early in the church’s history. It has recently been suggested that the Abbey stands on the site of the old Roman amphitheatre, and that St Peter’s Street, St Albans, marks the position of the Roman cursus, or race-course.