(1) Except as provided in Sentence (2), studs shall be doubled on each side of openings so that the inner studs extend from the lintel to the bottom wall plate and the outer studs extend from the top wall plates to the bottom wall plate.
(2) Single studs are permitted to be used on either side of openings,
(a) in non-loadbearing interior walls not required to have fire-resistance ratings, provided the studs extend from the top wall plate to the bottom wall plate, or
(b) in loadbearing or non-loadbearing interior or exterior walls, provided,
(i) the opening is less than and within the required stud spacing, and
(ii) no two such openings of full stud space width are located in adjacent stud spaces.