Church of St. Tysilio has 12th or 13th century roots, but has been thoroughly rebuilt in the early fifteenth century. In the early period of its existence, it was certainly owned by the nearby Valle Crucis Abbey. In 1718, the northern transept was added to the church, and in 1869 a Victorian restoration of the building was carried out.
The church was built of rubble stone and sandstone ashlar in the corners. The nave and the presbytery of the church formed a single whole, covered with a gable roof. From the south, the main entrance to the nave was preceded by a porch. The oldest windows were narrow, rounded at the top, and perhaps framed in carved patterns, as was the north window. In the late Gothic period, large, pointed windows filled with traceries were implemented. As the presbytery was not separated from the outside, inside the church the secular part had to be separated from the part of the priests by a wooden partition of the rood screen. The entire interior was covered with a wooden, open roof truss.
The original building was enlarged from the north by an early modern chapel attached to the presbytery. The oldest window from the 13th / 14th century has been preserved in the corner of the nave and chapel. The large Gothic window with a tracery in the eastern wall comes from the 15th century, while the currently hidden window in the chapel from the 14th century. Inside the church, there is a medieval roof truss, a 15th-century rood screen separating the nave from the presbytery, topped with an oak eagle and an octagonal baptismal font from the 15th century.
Salter M., The old parish churches of North Wales, Malvern 1993.
Website britishlistedbuildings.co.uk, Church of St Tysilio A Grade II Listed Building in Llantysilio, Denbighshire.