Listed buildings are placed in one of three grades, which give an indication of their relative importance - Grade I, Grade II* or Grade II.
Grade I and II* listed buildings are a small proportion (about 6% nationally) of all listed buildings.
They are particularly important to the nation's built heritage as buildings of outstanding architectural or historic interest. The remaining buildings are listed Grade II and represent an important part of our built heritage which is given special protection.
Grading can be changed where re-evaluation takes place after damage or alteration, or as more evidence of a building's history or architectural quality comes to light.
But the statutory controls on alterations apply equally to all listed buildings whatever the grade.