MB4 214a: Other Configurations Within an Enclosed Yard (358:12-14)
If a roof covers part of a large קרפף (more than a 2 סאה) then the two parts can be considered separate areas because of פי תקרה יורד וסותם even if the roof is slanted.
If an enclosed קרפף was exactly 2 סאה and the wall becomes breached making it larger than 2 סאה.
If a קרפף larger than 2 סאה wasn't enclosed not for dwelling purposes and a wall is built לשם דירה it can become מוקף לשם דירה and vice-versa.