Purchased a set of replacement sills N/s & O/s. the old ones are well past their sell by date, but can only get outer sills, do they require an inner sill?

14 minutes ago, lkuser said:

Purchased a set of replacement sills N/s & O/s. the old ones are well past their sell by date, but can only get outer sills, do they require an inner sill?

 

Depends on what the damage or corrosion is like,