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IRONWORK REPAIRS IN TIMBER-FRAMED BUILDINGS.
5. Types of iron ties.
5.14 Threaded Bolts.
Salzman believes that threaded bolts were introduced at the beginning of the
1500's but it appears unlikely that they were available commonly for at least
another hundred years. Screw threaded bolts were certainly being used in cathedral
work of the later 17th century. (Hewett CA, 1980).
Early threaded bolts
have very heavy heads, shanks and almost cuboid nuts (Fig 5.38) and this trend
continued into the late 1700's. By 1800 machine tools were being developed
that allowed the mass production of bolts and nuts. The forged bolts had square
heads but with a slight dome (Fig. 5.39) and the nuts became very much slimmer
Two bolts dated to 1714 by the accounts of Ashes Farm, Cressing, Essex. The
heads are heavy and flat topped and the nut not far off being a cube of metal.
A 19th century bolt head in the Horse Shelter at Cressing Temple. Built between
1842 and 1876 (from map evidence) all the hanging knees are bolted in place
with these distinctively headed bolts.
The other end of the bolt in Fig. 5.37 above. The nut is very much slimmer
than those of a hundred years earlier and it sits on a machine made washer.
The tip of the thread is blunt. Compare with Fig. 5.21.
Threaded bolts became
routinely used in the fabrication of buildings in the early to mid 1800's
where they were employed to bolt together trusses and secure hanging knees
(Fig. 5.41). Bolts up to the first half of the 19th century have sharp pointed
ends to receive the thread which has a swaged appearance. By the second half
of the 19th century the ends become blunt and the threads much sharper in
profile. (This is also a feature of tie-rods which are simply very long bolts).
By the early 20th century hexagonal headed bolts were freely available for
heavy engineering such as the building of steel framed buildings. It is very
unlikely to find an earlier hexagonal headed bolt or nut in a timber-frame
The Horse Shelter at Cressing Temple is a typical mid-Victorian farm building.
All the hanging knees are secured with wrought iron square-headed bolts. Repairs
to the 18th century Wagon Lodge, close by on the site, mimic this design exactly.
Stirrups are elongated U shaped straps whose terminals are specially forged
to receive bolts or gibs and cotters. They became popular in the late 1600's
as a way of reinforcing thin section trusses. Winchester cathedral has examples
of stirrups secured with forelock bolts dating to 1699 while Lincoln Cathedral
has stirrup, gibs and cotters dated to 1762. (Hewett CA, 1980). None were
observed used as repairs during field work and this may be because of the
difficulty of precisely cutting the housing for the gibs and cotters. They
are also unnecessarily complicated for a simple repair.
5.16 Composite ties.
This is a term here employed to describe a tie that has more than one component
to effect its use (Fig. 5.42). Tie rods or bars with special terminals may
be considered as composite ties but their form is commonplace. Unusual forms
need to have their characteristics closely examined to determine a period
A composite tie on the front of the Marlborough Head public house, Dedham,
Suffolk. This resembles the pin tie found in the Wheat Barn at Cressing Temple
(Fig. 5.27) but it has been passed through a face-plate to secure the joint.
Note on Reworked and Re-used Iron.