Couple close roof sketch

In a simple couple roof, pairs of rafters meet at the ridge and rest on wall plates without any tie, so they push the walls outward (span about 3.6 m). Adding a tie at the feet of each pair gives the couple-close roof.

A couple-close roof is a single roof in which each pair of common rafters meeting at the ridge has its feet connected by a horizontal tie beam. The tie takes the horizontal thrust, so only vertical loads reach the walls. Span about 4.5-5 m.

          ridge
           /\
          /  \ rafters
         /    \
        /      \
     __/________\__
    wall plate  tie beam  (wall plate)

Features:

• Rafters about 50 x 100 mm to 50 x 125 mm at 400-600 mm c/c, ridge piece 40 mm thick; tie beam 50 x 100 mm or more.
• Rafters are notched/spiked to the wall plate and tie.
• Advantage: no outward thrust, simple. Limitation: the rafters sag if the span exceeds 5 m, so a collar roof or double roof is used.
• Used for small houses, sheds and verandahs.