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Graphical Construction Glossary >> Roofs and roofing. >> Roof Trusses >> Raised cruck

Raised Cruck
A cruck truss that is raised to sit on usually short walls. Either masonry or timber.
Buttress
A mass of masonry bonded to an exterior wall. Usually to stiffen it against the lateral thrust of roof structures.



the reason for raised crucks

Given that trees of a certain kind only grow to a particular size the early cruck builders had two choices, either make the structure wider at the expense of less height, using center columns as needed, or to go higher but with less width.

To a certain extent the raised-cruck gave builders the best of both worlds. Either using timber walls or if a good source of stone was available then masonry walls.

a raised cruck truss

a raised cruck
The interior of the tythe barn at Pilton in Somerset, England was built in the 14Th century to hold produce for Glastonbury Abbey.
Photo thanks to Wikipedia. Go there for a larger version if you wish to copy it.

This interior view shows the space and height required to allow large hay wains and drays to be able to comfortably unload and store large quantities of produce.

pilton tythe barn
The exterior of the tythe barn at Pilton in Somerset.
Photo thanks to Wikipedia. Go there for a larger version if you wish to copy it.

Because of the lack of tie beams on the raised-cruck-trusses these roofs exerted tremendous outwards thrust on the supporting walls. The answer was to build stone buttresses at the truss positions to stop the wall spreading.



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