The original pre-Norman church was recorded in the 12th-century Book of Llandaff to have been no more than 28 feet (8.5 m) long, 15 feet (4.6 m) wide and 20 feet (6.1 m) high.
It contained low, narrow aisles with an apsidal porticus measuring 12 feet (3.7 m) long.
Construction began of a grander building under the orders of the second Norman bishop of Llandaff, Urban, in the 1120s, to administer power over the newly formed diocese.
It doesn't appear to have lasted long as an extensive construction was ordered between 1193 and 1218 during the episcopate of Henry of Abergavenny.
The western parts replaced those that Urban had built, and the nave and front of this side remain today.
The fine craftsmanship and subtlety of the architecture show a clear similarity to those of Glastonbury Abbey and Wells Cathedral, so it is probable that several of the leading craftsman of Somerset were hired for the building.

Though some remodeling work was done in the 13th and 14th centuries, with a northwest tower funded by Jasper Tudor, lord of Glamorgan from 1484–95, by the late 16th century the church had fallen into a state of disrepair.
In 1594 the bishop complained that the cathedral was "more like a desolate and profane place than like a house of prayer and holy exercises".
The church continued to exist in a poor state, so that by 1692 choral services had to be suspended in fear that the roof would collapse.
The battlements of the northwestern tower blew away during a storm in 1703, and the southwest tower fell down in 1722.
In 1734, John Wood of Bath was hired to restore the cathedral, but his work on the temple was still not complete by 1752 and remained that way.
 It was not until 1840 that in the wake of industrial development in Cardiff that the cathedral could raise the funds to commence a full restoration.

T. H. Wyatt was hired to restore the Lady Chapel in 1841, but due to other commitments later left much of the work to John Prichard, who worked the most extensively on the church in the 1840s and 1850s.
Prichard had restored the sanctuary by 1850, and by 1852 he had begun to work on the nave, largely demolishing much of the temple Wood had built.
 Together with London-based John Pollard Seddon, who was able to hire pre-Raphaelite artists Dante Gabriel Rossetti and Thomas Woolner, extensive developments were made.
Morris & Co. provided the stained glass in the 1860s.
Prichard was responsible for a dramatic redevelopment of the southwest tower in 1867–1869, aided by a number of talented artists and craftsmen.

In 1941, a parachute mine exploded near the south aisle of the cathedral, resulting in the roof of the nave collapsing and the shattering of the windows.
Sir Charles Nicholson was hired to rebuild the roof, and made the decision to remove the altarpiece that Rossetti had added to the north aisle.
In 1949, Nicholson was replaced with George Pace of York, who in coordination with the dean at the time, Glyn Simon, saw a number of improvements in the modern style, though many fittings were clearly still influenced by the Gothic.

The material of the church which remains from the medieval period is primarily Somerset Dundry stone, though Sutton stone and local blue lias also make up the stonework, with the latter constituting most of the stonework done in the post-Reformation period.
The work done on the church since World War II is primarily concrete and Pennant sandstone.
The roofs, added in the post-war period, are made of Welsh slate and lead.
The West front of the cathedral is gabled along its length and contains the grand central doorway, higher in level than the floor of the nave.
It is described as being "double lobed" with an "arched head with continuous chamfer outline, colonnettes and dripmould".

The south side of the nave is characterized by eight bays with stepped buttresses between them, with aisle windows featuring reticulated heads.
At the side of the south aisle of the sanctuary is Chapter House, a small, two story square building.
It dates to the mid 13th century and is made from Chipping Camden and Bath limest
The original pre-Norman church was recorded in the 12th-century Book of Llandaff to have been no more than 28 feet (8.5 m) long, 15 feet (4.6 m) wide and 20 feet (6.1 m) high. It contained low, narrow aisles with an apsidal porticus measuring 12 feet (3.7 m) long. Construction began of a grander building under the orders of the second Norman bishop of Llandaff, Urban, in the 1120s, to administer power over the newly formed diocese. It doesn't appear to have lasted long as an extensive construction was ordered between 1193 and 1218 during the episcopate of Henry of Abergavenny. The western parts replaced those that Urban had built, and the nave and front of this side remain today. The fine craftsmanship and subtlety of the architecture show a clear similarity to those of Glastonbury Abbey and Wells Cathedral, so it is probable that several of the leading craftsman of Somerset were hired for the building.
Though some remodeling work was done in the 13th and 14th centuries, with a northwest tower funded by Jasper Tudor, lord of Glamorgan from 1484–95, by the late 16th century the church had fallen into a state of disrepair. In 1594 the bishop complained that the cathedral was "more like a desolate and profane place than like a house of prayer and holy exercises". The church continued to exist in a poor state, so that by 1692 choral services had to be suspended in fear that the roof would collapse. The battlements of the northwestern tower blew away during a storm in 1703, and the southwest tower fell down in 1722. In 1734, John Wood of Bath was hired to restore the cathedral, but his work on the temple was still not complete by 1752 and remained that way.  It was not until 1840 that in the wake of industrial development in Cardiff that the cathedral could raise the funds to commence a full restoration.
T. H. Wyatt was hired to restore the Lady Chapel in 1841, but due to other commitments later left much of the work to John Prichard, who worked the most extensively on the church in the 1840s and 1850s. Prichard had restored the sanctuary by 1850, and by 1852 he had begun to work on the nave, largely demolishing much of the temple Wood had built.  Together with London-based John Pollard Seddon, who was able to hire pre-Raphaelite artists Dante Gabriel Rossetti and Thomas Woolner, extensive developments were made. Morris & Co. provided the stained glass in the 1860s. Prichard was responsible for a dramatic redevelopment of the southwest tower in 1867–1869, aided by a number of talented artists and craftsmen.
In 1941, a parachute mine exploded near the south aisle of the cathedral, resulting in the roof of the nave collapsing and the shattering of the windows. Sir Charles Nicholson was hired to rebuild the roof, and made the decision to remove the altarpiece that Rossetti had added to the north aisle. In 1949, Nicholson was replaced with George Pace of York, who in coordination with the dean at the time, Glyn Simon, saw a number of improvements in the modern style, though many fittings were clearly still influenced by the Gothic.
The material of the church which remains from the medieval period is primarily Somerset Dundry stone, though Sutton stone and local blue lias also make up the stonework, with the latter constituting most of the stonework done in the post-Reformation period. The work done on the church since World War II is primarily concrete and Pennant sandstone. The roofs, added in the post-war period, are made of Welsh slate and lead. The West front of the cathedral is gabled along its length and contains the grand central doorway, higher in level than the floor of the nave. It is described as being "double lobed" with an "arched head with continuous chamfer outline, colonnettes and dripmould".
The south side of the nave is characterized by eight bays with stepped buttresses between them, with aisle windows featuring reticulated heads. At the side of the south aisle of the sanctuary is Chapter House, a small, two story square building. It dates to the mid 13th century and is made from Chipping Camden and Bath limest
Llandaff Cathedral