Reciprocal Roofs — 6 Comments

  1. The forces acting on a reciprocal roof result in two things; 1) the beams twist under load in non-dimensional timber (ie logs), and 2) bending or sagging under load, or with time. It is the latter which can effect walls, but under all but major overload conditions this is trivial, and can usually be safely ignored. One or two inches of deflection is trivial in an eight foot wall, and this would represent a very large deflection in a reciprocal roof. Most of the forces involved cause a twisting effect which doesn’t appear to have any serious spreading forces on the walls.

  2. i knew the yurt relied on tension bands to stop the roof from pushing the yurt walls out. but i thought reciprical roofs were very different and only excert downwood pressure. therefore a tension band or equivelent was not required. am i mislead?

  3. I might mention that these reciprocal roof systems are very similar to a typical yurt roof design, with the rafter poles themselves forming the circular interior compression ring. As with yurt roofs, they need to be tied securely where they connect with the wall so that they stay put, and there needs to be a strong tension band or bond beam around the perimeter at the top of the wall to keep the roof from depressing and tending to expand the wall at that point.

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