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I have, of late, been building a barn*. It's not huge - about
equivalent of three one-car garages side by side. It came
a kit - sort of a giant oak Jenga.
The roof is fairly straightforward - it has a ridge shorter
the building, and hips (ie slopey bits) at each end, as well
sloping front and back. Putting it up single-handed** has
a bit of a faff.
A bit of thought suggests that there's a better way. Provide
fixings which attach the rafters, at their top ends, to the
ridge, with hinges***. In this way, the whole roof would be
of like a rectangular umbrella. The bottom ends of
pairs of rafters would be tied together (temporarily) to stop
them spreading out more than intended.
Then - gadulka! Assemble the roof on the floor of the
building, then lift the ridgepole up (higher than its normal
position). Open out the rafters, drop the roof down onto
walls, fix down the ends of the rafters, remove the tethers
and you are good to go.
Yes, I know you can buy ready-assembled single roof
but this isn't that kind of roof.
(*You have to do something over the Christmas break.)
(**Yes, I know I should use two hands.)
(***The hinge would be at the bottom end of the rafter,
where it meets the bottom edge of the ridge. Hinges are
not necessarily very strong, but this joint is in heavy
compression when the roof is finished. For added strength,
spikes on the end of the rafter would bite into the ridge
when the joint is closed.)
||At it's inevitable conclusion skyscrapers would be put up in this manner. You might need a rocket or two to lift them.
||Are the ceiling joists, which tie the two sides of the
structure together, part of the mechanism?
||//ceiling joists// This particular roof has no joists.
There are 4 big tie-beams that run from front to back
(one at each end of the building, and two at the
1/3rd and 2/3rds points)
so, they are effectively very big joists, but they're
part of the main structure rather than the roof. The
roof itself, viewed in section from front to back,
consists of a series of inverted V's, rather than A's.
The bottom ends of the inverted V's are notched to
sit on the oak beams that run left-to-right.
||(The hipped ends are basically the same idea.)
||Rockets were also my first thought. A tethered drone could provide hours of amusement for the neighbours. (hmm).
||I was thinking about helium balloons. But the weight
isn't really an issue. I lifted the horizontal oak beams
(some of which weigh maybe 500lb) with a mini-
digger. The whole roof (minus tiles and battens)
weighs maybe 500-800lb. I think I could lift it either
with the minidigger (which might not reach high
enough), or by the cunning use of ratchet-straps
(which I used to lift some of the bigger components).
||A couple of drones, attached to the ridge of the umbrella'd roof, powered by a groundbound genset. Fly the ridge up, incidentally clearing the concrete dust out of the building, set to "hover", and start tacking the beams to the top of the walls.
||Or mess about with telephone poles and pulleys.