The church begun by Abbot Paul of Caen (1077-93) in 1077 had an aisled eastern arm of 4 bays; the central vessel with an apse and the aisles perhaps apsed too (see Fernie 2000, 112), although nothing has been found to clarify the arrangement.The cruciform church had 3-bay transepts; the inner bays corresponding to the nave and chancel aisles, with a pair of stepped chapels on the E side of each. The exterior view from the east would thus have shown an echelon of 7 apses. The nave was originally of 10 bays. The nave elevation is of 3 storeys with a tribune gallery and clerestorey above the arcade. As a whole the articulation is very plain with practically no shafts, probably a result of the building materials used in the construction. The church is largely of flint with re-used Roman brick taken from the Roman site of Verulamium used for strengthening and as dressing where right angles were needed.

The new church was consecrated in 1115, in the abbacy of Abbot Paul's successor Richard d'Aubeney (1097-19), then from the end of the 12thc, Abbot John de Cella lengthened the nave by 3 bays, rebuilding the westernmost bay in the process. He also commissioned a new W front from Hugh of Goldclif, described by Matthew Paris as 'an untrustworthy and deceitful man, but a consummate craftsman'. True to form, Goldclif used up all the money and kept demanding more until the abbot could stand it now longer. Goldclif was dismissed and the incomplete facade left to crumble for want of funding to complete it. After more several delays the W end was eventually completed c.1230 under Abbot William of Trumpington (1214-35). The eastern arm was rebuilt and extended eastwards in the 13th; the work beginning with a rebuilding of the choir aisles from 1235, and including a new presbytery, a feretory for the shrine of St Alban, a retrochoir and a Lady Chapel at the E end. The last of these was completed early in the 14thc. In 1323 bays 5 to 9 of the S nave arcade were rebuilt (to match the Early English work further west) following a collapse.

After the Dissolution of the abbey in 1539 the monastic buildings were sold to Sir Richard Lee for building materials, and the church passed to the town. The east end was converted into a Grammar School, and the remainder became a parish church, apparently ill-maintained. Part of the S nave wall fell through the aisle roof in 1832, and repairs were carried out by L. N. Cottingham. A campaign of restoration was carried out by Sir Gilbert Scott from 1856 to 1877, and he restrored the S nave clerestorey, reroofed the S aisle restored the Lady Chapel and stabilised the crossing tower. He also reunited the E end with the rest of the church. Restoration was continued by Lord Grimthorpe after Scott's death, and his approach was much more intrusive. In the 1880s and '90s he completely rebuilt the west front and the transept facades as well as restoring the Lady Chapel, eastern arm and nave, all at his own expense, and he was heavily criticized for his approach. Meanwhile in 1877 the diocese of St Albans had been consituted, with the abbey as its cathedral. The see initially covered Hertfordshire, Bedfordshire and Essex, although the last of these gained its own see at Chelmsford in 1914.

We are indebted to Matthew Paris, a 13thc monk of St Albans, for the earliest account of the foundation of the abbey. According to this, King Offa II of Mercia founded it under the direction of an angel who visited him in the night and instructed him to provide a fitting shrine for St Alban, the first British Christian martyr. Following a synod in 793 it was decided to establish a monastery to house the relics at Verulamium, the place of his martyrdom. Offa and his son Egfrith gave endowments of land and liberties to the new monastery, and Willigod the priest was appointed its first abbot. At the Conquest the abbot was Frederic, appointed by Harold II. William was well aware of the resistance to his rule in East Anglia, which he exacerbated by stripping St Albans of many of its lands and giving them to Westminster. Frederic was a staunch opponent of the Conqueror, attempting to put Edgar Aethling on the throne, and when Edgar submitted to William, Frederic adminstered the oath whereby William swore on Alban's relics to be a good lord to them. He may have been involved in the rebellions of 1075-76; at any rate he left the convent and fled to the Isle of Ely where he died shortly afterwards. Paul of Caen, a kinsman of Archbishop Lanfranc replaced Frederic in 1077, apparently reforming the customs of the abbey, founding a scriptorium, and attracting endowments from the new Norman elite.

It has been suggested that the baluster shafts in the E triforia of both transepts were reused from pre-Conquest material (Fernie (2000), 115). This is probably the case as they differ in their designs and there is some evidence of variations in their lengths which have been adjusted to fit their present positions. When the supply of baluster shafts ran out, some attempt at an alternating system of octagonal and cylindrical shafts was made, but not with any regularity. All of the capitals in this part of the church are cushions with angle tucks or double scallops with angle tucks, and the central shaft of each bay is usually doubled, but not in the E triforium of the S transept or the 1st bay of the E triforium of the N transept. This suggests that the E wall of the transept began before the W and the S before the N. The replacement shafts in the W triforium of the S transept date stylistically to c.1170-90.

The sumptuously carved blind arcading from the slype, and the doorway formerly linking the slype and the cloister contrast strongly with the simplicity of the transept in which they are now housed. The capitals of the blind arcade include the Byzantine blossom, a variant of the trefoil scallop, furled leaves and lilies with a lavish application of beading. All of this places the work in a direct line from the cloister sculpture of Reading Abbey but it is clearly later in the sequence, dating from c.1140-60. While the Reading sculpture is of Oolitic limestone, that at St Albans in of clunch or Totternhoe, the material of the Aylesbury group of fonts, and as Thurlby (2001) has already demonstrated there are sufficient similarities to suggest that some of the St Albans sculptors, or their workshop descendants, may have gone on to produce the better of them.