Bryn Sion Methodist Chapel was first built in 1862 and rebuilt in 1899 to the design of architect Roderick Thomas of Aberdare. The present chapel, dated 1899, is built in the Simple Sub-Classical style of the gable-entry type. It has two storeys, with a large Hall/Sunday school to the rear of the chapel and a long narrow splayed room (vestry) to the right of the hall. The building was internally modified in 1930, when a coffered ceiling was inserted, and in the 1970's when an immersion-font was installed as the chapel became Baptist. Carml (Bryn Seion) is now Grade 2 Listed as a 'prominent nineteenth century chapel with a particularly elaborate inter-war classical ceiling'.

RCAHMW, April 2010