High up on the north side of the Chapel (facing on approach from the visitor centre) is a series of shields with the following inscriptions –
W L S F Y C Y Z O G MIII1L
which translates as
William Lord St Clair Fundit Yis College Ye Zeir Of God MCCCCL (1450)
This suggests that the foundations took four years to complete, as it is believed that the Chapel was founded in 1446.
There are carvings on all of the Chapel’s outside walls although some are hard to distinguish due to the effects of the weather. On the north wall is a carving of fox running off with a goose, with the farmer’s wife close behind. On the south side, many faces are carved into the window arches along with animals, such as a stag and ram. The west wall shows how the Chapel was originally intended to be a much bigger building with doorways, which would have led to a nave, now blocked up and other features which would not normally be found on exterior walls, as this was not planned to be one. The Baptistery, on the west end, was added in 1880.