At the W end is a large and important Norman tower.
Otherwise the S elevation presents the two-storey embattled S porch in the second bay from the W, the gable of the S transept and the Norman chancel.
Inside the porch is stone vaulted between its two stages and has a large carved boss in the centre.
A fragment of Saxon interlace, perhaps of the 10th-century, is built into the exterior of the S transept W wall.
The Norman chancel is faced with ashlar blocks and has a corbel table of grotesque heads round it at eaves level.
Below it is a highly unusual area of Norman chequerwork decoration cut into it in situ.
On the N of the chancel is a vestry under a catslide roof and having a series of reused Norman heads in the corbel table.
The arches from the aisles to the transepts have ornate decorative work of the Perpendicular period, the soffits being carved with a foliage trail.
There are many fragmentary remains of wall paintings.
In the gable over the chancel arch is a 16th-century vine-trail.
Beneath the chancel and approached via a trap door is a crypt, 2.82m E-W and 3.2m N-S. This is appears to be pre-Conquest, having been filled in when the Norman chancel was built.
The octagonal font, decorated on its bowl with quatrefoils and panelling on its base is Perpendicular: its plain cover, of ogee shape, is Jacobean.
At the W end of the nave the gallery survives, dating from 1620 but altered in 1754.
At the W end of the S aisle are four 17th-century charity boards.
There is stained glass of 1899, 1902 and 1906 by Kempe.
The small crypt under the chancel is thought to be Saxon and probably represents a relic chamber.
Post-Reformation activity can be traced through the W gallery and font cover.
The Buildings of England: Devon, 1989, pp 731-2.
REASONS FOR DESIGNATION: The church of St Giles and St Peter, Sidbury, is designated at Grade I for the following principal reasons: * It is of outstanding interest as a church with a long structural history, probably stretching back to Saxon times as represented by the crypt. * The church contains important Norman and Transitional fabric along with work of the 13th century and the Perpendicular period.
The vaulting in the tower, the treatment of the arches from the aisles to the transepts and the decoration of the roofs is of particular interest. * It contains various fixtures of interest, notably the W gallery, font and cover and a series of high quality items of c1900 designed by the architect Walter Cave FRIBA whose family lived at nearby Sidbury Manor.