The Ontario Building Code | Openings in Loadbearing Walls
(1) openings="http://thehandyforce.com/windows/" title ="Window installer in Toronto">openings in loadbearing walls greater than the required stud spacing shall be framed with lintels designed to carry the superimposed loads to adjacent studs.
(2) Except as provided in Sentence 18.104.22.168.(2), where two or more members are used in lintels, they shall be fastened together with not less than 82 mm nails in a double row, with nails not more than 450 mm apart in each row.
(3) Lintel members may be separated by filler pieces.