This animation shows the construction of a twisted brick pillar, 440 by 440mm and offset by 10 degrees
Due to the lack of plumbing points, it can sometimes be difficult for beginners, to keep such spirals absolutely up-right
One method is to use triangular templates and rest these on the corners
A better method is to use a timber-board, cut to the right shape, and threaded onto a central steel rod, see diagram
One method is to use triangular templates and rest these on the corners
A better method is to use a timber-board, cut to the right shape, and threaded onto a central steel rod, see diagram
Image from Bricklaying
by Cartwright, pg 268
by Cartwright, pg 268
Calculating the offset angle
Although an angle of 20° would make the pillar twist round quicker, there are some design issues
Not only would the frog be seen, but the offset at the corner is over ¼-brick
This makes the structure behave like corbelling and
it is likely to become unstable
Offset at 20°, shaded
Not only would the frog be seen, but the offset at the corner is over ¼-brick
This makes the structure behave like corbelling and
it is likely to become unstable
Usually, oversailing is no more than 28mm, which means reducing the angle
of twist, and so increasing the number
of brick courses, before the pillar turns
a full circle
10° is often used, since this gives nine courses for a quarter-turn
The black and white photo shows the twisted chimney at Buckingham
It was built over 500 years ago!
Image from:A History of English Brickwork
by Nathaniel Lloyd, page 341
by Nathaniel Lloyd, page 341
More recent examples are shown below...
Unfortunatley this arch was demolished in 2014.
ReplyDeletethis was truly a work of art been a bricklayer all my working life and never seen one like this .i would have liked to have had ago at constructing one like this.can you imagine these on a modern housing site they w0uld all be made out of fiber glass .as are most arches now
ReplyDelete