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A traditional timber frame uses a bent
system--in part, specifically to facilitate
raising the frame. The bent assembly represents a
cross section of the structure, including posts,
tie beam, and rafters. The bents are trial
assembled in the shop, to ensure an exact fit.
Then they are taken apart, coded, and stacked to
await shipment. |
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At the time of the raising, the timbers are first
assembled on the ground. The bent that will go up last is
assembled first, followed by the next in order of
placement, with the first bent to be raised on the top of
the pile. The crane lifts the first bent up and places it
on the floor deck. It is braced to hold it steady while
the connecting girts are fitted into the bent. They too
are braced. The next bent is flown in by the crane and
connected up with the girts. Once the two bents are tied
together by the connecting girts, we have a more stable
structure to work on.
After the bents are secured with connecting girts, the
loft floor joists are flown in and installed in the loft
area. Finally, the ridge beam and roof purlins are flown
in and dropped into their housings on the rafters. The
area defined by two bents and these horizontal members
(connecting girts, purlins, and joists) is called a bay.
We find that it generally takes the Goshen crew
approximately two days to assemble and raise a 3- to
4-bent frame, such as standard frames Blackberry Cove and
Walnut Creek. A larger frame, with side sheds (such as
Sugar Fork) may take up to three days. The conditions of
the site have a bearing, of course, since it is a very
different proposition to raise a frame on a steep slope
which limits crane access compared to raising a frame on
level ground.
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Common rafter frames are constructed with
horizontal plates running through the structure.
The rafters are set on the plates, usually on 2'
to 4' centers. There are no purlins in a common
rafter frame.
This system, too, serves a purpose in terms of
the raising, especially of very large frames,
since the bents might become so large that they
would be dangerously heavy. When raising a common
rafter frame, the bent posts are raised in
sections and topped with the plates, which tie
them together. Then loft floor joists are seated.
Finally, the rafters are flown in and seated on
the plates. |
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In general, common rafter frames are quickly and easily
raised. However, a large common rafter frame, such as
Goshen's Gentry's Mill, can take a considerable amount of
time, because there are so many separate timbers to be
installed piece by piece with the crane. Consequently, we
plan on 3 to 4 days to raise this frame. |
