In areas with supplies of wood, many dwellings were made of posts pushed
into the ground to keep them upright. Other wooden members, also made from
young trees and branches, were added to give rigidity, and a thatched roof
However, the posts rotted where they contacted the ground and the dwelling
usually lasted no more than a generation. At about this time came the First
Technological Breakthrough: the use of a stone plinth and timber sill along
with the use of strong timber joints.
The stone plinth consisted of a line of stones, perhaps partly below ground
as well as above, laid along the foot of walls. On this was placed a sturdy
wooden sill, usually of oak and shaped to a rectangular cross-section with a
broad axe and then by an adze. Upright posts, also rectangular, were then
inserted into the sill and secured by mortise and tenon joints held together
by oak pegs. Iron was seldom used because it was precious and the acid in
the oak could corrode it.
The mortise and tenon joint is exceptionally strong and rigid. There are
five main ways in which any structural member can fail:
Shearing occurs when there is an attempt to slide parts sideways, If the
pegs failed they would do so mainly in shear while resisting the pulling out
of the tenon. Also, the shoulders of the tenon would strongly resist any
attempt to alter the angle between the mortise and the tenon. The plinth
raised the wood above the main source of damp, the ground.
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