The description of the Bashing shield quality states:
A shield with this special ability is designed to perform a shield bash. A bashing shield deals damage as if it were a weapon of two size categories larger (a Medium light shield thus deals 1d6 points of damage and a Medium heavy shield deals 1d8 points of damage). The shield acts as a +1 weapon when used to bash. Only light and heavy shields can have this ability.
Since it states that "Only light and heavy shields can have this ability", does this mean spiked light and heavy shields cannot have this ability?
If they can have this ability, then how much damage would the spiked heavy and light shields do?