IRONWORK REPAIRS IN TIMBER-FRAMED BUILDINGS.
Why do timber frames
2.2 Materials failure
- early failure due to greenness/ warping/ springing out/ shrinkage - inherent
was not far-reaching and carpenters were blinkered by Guild practices (Swanson.H,
1983) from looking closely at other professions to gain insight into the mechanical
properties of green timber. Green timber, that is timber freshly cut and used
without being seasoned, was employed because the hand tools available in the
mediaeval period were only strong enough to cut soft materials. However, green
timber has a huge water content that increases the weight up to ten-fold from
a fully dried out sample. The carpenter probably associated weight with strength.
If the building was constructed
from green timber over a typical period of six months it might then be subjected
to a rapid drying out during a hot summer. In this case the joints would all
shrink, the pegs loosen, the dovetails spring and any number of timbers warp.
This would probably not be disastrous but would need addressing. Carpentry
joints could be firmed up with larger pegs and wedges and perhaps some auxiliary
However, what is more
likely is that the drying out would be prolonged over several decades and
that it would occur differentially, the south side of the building drying
first with all its concomitant problems. By then the frame has been buried
in the internal décor and even rendered externally. Wholesale repairs
would no longer be an easy option and so localised iron-work repairs would
be installed to arrest any further movement. This approach would have to be
There is also the possibility
of inherent faults, not detected in the green stage in the timber, leading
to an early failure under loading, drying out or mechanical damage.