Suger began his rebuilding project at the western end of St Denis, demolishing the old Carolingian westwork, with its single, centrally located door.
He extended the old nave westwards by an additional four bays and added a massive western narthex, incorporating a new façade and three chapels on the first floor level.
This new façade, 34 metres (112 ft) wide and 20 metres (66 ft) deep, has three portals, the central one larger than those either side, reflecting the relative width of the central nave and lateral aisles.
This tripartite arrangement was clearly influenced by the late 11th-century façades of the abbey churches of St Etienne and La Trinité, Caen,  with which it also shared a three-storey elevation and flanking towers.
 Only the south tower survives; the north tower was dismantled following a tornado which struck in 1846.

The major innovation in the façade at St Denis is the way the unknown architects have chosen to emphasise the divisions between the different parts with massive vertical buttresses separating the three doorways and horizontal string-courses and window arcades clearly marking out the divisions.
 This clear delineation of parts was to influence subsequent west façade designs as a common theme in the development of Gothic architecture and a marked departure from the Romanesque.
 The rose window at the centre of the upper storey of the west portal was also innovative and influential.
 Although small circular windows (oculi) within triangular tympana were common on the west facades of Italian Romanesque churches, this was probably the first example of a rose window within a square frame, which was to become a dominant feature of the Gothic facades of northern France (soon to be imitated at Chartres Cathedral and many others).
The overall design of the façade has an obvious resemblance to a Roman city gatehouse (an impression strengthened by the buttresses and by the crenellations around the top), which helps to emphasise the traditional notion of great churches as earthly embodiments of the Heavenly City, as described in the Book of Ezekiel.

The many influential features of the new façade include the tall, thin statues of Old Testament prophets and kings attached to columns (jamb figures) flanking the portals (destroyed in 1771 but recorded in Montfaucon's drawings).
These were also adopted at the cathedrals of Paris and Chartres, constructed a few years later, and became a feature of almost every Gothic portal thereafter.
Above the doorways, the central tympanum was carved with Christ in Majesty displaying his wounds with the dead emerging from their tombs below.
Scenes from the martyrdom of St Denis were carved above the south (right hand) portal, while above the north portal was a mosaic (lost), even though this was, as Suger put it 'contrary to the modern custom'.
Of the original sculpture, very little remains, most of what is now visible being the result of rather clumsy restoration work in 1839.
Some fragments of the original sculptures survive in the collection of the Musée de Cluny.

The portals themselves were sealed by gilded bronze doors, ornamented with scenes from Christ's Passion and clearly recording Suger's patronage with the following inscription; 
For the glory of the church which nurtured and raised him, Suger strove for the glory of the church, Sharing with you what is yours, oh martyr Denis.
He prays that by your prayers he should become a sharer in Paradise.
The year when it was consecrated was the one thousand, one hundred and fortieth year of the Word.

 
On the lintel below the great tympanum showing the Last Judgement, beneath a carved figure of the kneeling Abbot, was inscribed the more modest plea;
Receive, stern Judge, the prayers of your Suger, Let me be mercifully numbered among your sheep.

Suger's western extension was completed in 1140 and the three new chapels in the narthex were consecrated on 9 June of that year.
Suger began his rebuilding project at the western end of St Denis, demolishing the old Carolingian westwork, with its single, centrally located door. He extended the old nave westwards by an additional four bays and added a massive western narthex, incorporating a new façade and three chapels on the first floor level. This new façade, 34 metres (112 ft) wide and 20 metres (66 ft) deep, has three portals, the central one larger than those either side, reflecting the relative width of the central nave and lateral aisles. This tripartite arrangement was clearly influenced by the late 11th-century façades of the abbey churches of St Etienne and La Trinité, Caen,  with which it also shared a three-storey elevation and flanking towers.  Only the south tower survives; the north tower was dismantled following a tornado which struck in 1846.
The major innovation in the façade at St Denis is the way the unknown architects have chosen to emphasise the divisions between the different parts with massive vertical buttresses separating the three doorways and horizontal string-courses and window arcades clearly marking out the divisions.  This clear delineation of parts was to influence subsequent west façade designs as a common theme in the development of Gothic architecture and a marked departure from the Romanesque.  The rose window at the centre of the upper storey of the west portal was also innovative and influential.  Although small circular windows (oculi) within triangular tympana were common on the west facades of Italian Romanesque churches, this was probably the first example of a rose window within a square frame, which was to become a dominant feature of the Gothic facades of northern France (soon to be imitated at Chartres Cathedral and many others). The overall design of the façade has an obvious resemblance to a Roman city gatehouse (an impression strengthened by the buttresses and by the crenellations around the top), which helps to emphasise the traditional notion of great churches as earthly embodiments of the Heavenly City, as described in the Book of Ezekiel.
The many influential features of the new façade include the tall, thin statues of Old Testament prophets and kings attached to columns (jamb figures) flanking the portals (destroyed in 1771 but recorded in Montfaucon's drawings). These were also adopted at the cathedrals of Paris and Chartres, constructed a few years later, and became a feature of almost every Gothic portal thereafter. Above the doorways, the central tympanum was carved with Christ in Majesty displaying his wounds with the dead emerging from their tombs below. Scenes from the martyrdom of St Denis were carved above the south (right hand) portal, while above the north portal was a mosaic (lost), even though this was, as Suger put it 'contrary to the modern custom'. Of the original sculpture, very little remains, most of what is now visible being the result of rather clumsy restoration work in 1839. Some fragments of the original sculptures survive in the collection of the Musée de Cluny.
The portals themselves were sealed by gilded bronze doors, ornamented with scenes from Christ's Passion and clearly recording Suger's patronage with the following inscription; 
For the glory of the church which nurtured and raised him, Suger strove for the glory of the church, Sharing with you what is yours, oh martyr Denis. He prays that by your prayers he should become a sharer in Paradise. The year when it was consecrated was the one thousand, one hundred and fortieth year of the Word.
 
On the lintel below the great tympanum showing the Last Judgement, beneath a carved figure of the kneeling Abbot, was inscribed the more modest plea;
Receive, stern Judge, the prayers of your Suger, Let me be mercifully numbered among your sheep.
Suger's western extension was completed in 1140 and the three new chapels in the narthex were consecrated on 9 June of that year.
Basilica of Saint-Denis