After ruling out any underlying structural problems, fill gaps of up to 1” (25mm) wide between the doorcase and wall using lime mortar.
Ar ôl diystyru unrhyw broblem strwythurol sylfaenol, llenwch unrhyw fylchau hyd at 1" (25mm) o led rhwng ffrâm y drws a'r wal gan ddefnyddio morter calch.