Complex sentence: A century later, a timber porch was built on the north side, the chancel arch was widened and a rood screen was installed, a standard feature of churches in the medieval era, as were wall decoration and paintings.
Split into simpler sentences: A century later, a timber porch was built on the north side, the chancel arch was widened and a rood screen installed. This was a standard feature of churches in the medieval era, as were wall decoration and paintings.