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NOTES REGARDING PERIMETERS |
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01 |
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P1 is the outer perimeter
of the concrete footing or trench |
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P2 is the centre-line
perimeter (CLP) of outer 'spread' or 'projection' of footing -- this projection
is 120 wide |
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P3 is the perimeter along
outer face of wall -- usually 103 Engineering bricks / Facings -- this wall
is also called 'outer skin of cavity wall' |
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P4 is the CLP of the 103
thick wall |
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P5 is the CLP of the 100
wide cavity |
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P6 is the CLP of the
footing -- note the cavity wall -- which is 343 wide -- sits centrally on the
footing |
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P7 is the CLP of the
inner skin of cavity wall -- 140 block wall in this case |
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P8 is the perimeter along
the inner face of the 140 block wall |
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P9 is the CLP of inner
projection or spread. |
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P10 is the perimeter
along inside footing or inner face of trench |
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02 |
It is good practice to
label the perimeters (P1,P2 etc) for easy reference later. Taking them in
diminishing order gives a visual check regarding results. |
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03 |
Many text books 'talk
about' 4 times twice times half times which is confusing AND they usually
mention 'centre line perimeters' whereas 'perimeters' would be the more
correct terminology |
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04 |
In my method, once a Known
Perimeter is established (in this case P3), all that is required is to
calculate the horizontal distance from the known perimeter to each 'required
perimeter' (RP) -- multiply this by a constant of 8 and either add or deduct
it to or from the KP |
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05 |
This method always works
where the plan shape has 90 degree corners and there are no 'gaps' in the
footing |
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06 |
It is essential that all
perimeters are checked before using the data in the quantities. Some computer
programmes allow typing in a 'code' (eg P1, P9) into the dim column and the
actual perimeter appears in it's place |
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