Had a sub pour a couple of decorative slabs today. 1 was straight sided (10
x 24) and the other was shaped like an egg/pear/water drop. (about 12 x 20)
& definitely not round with NO straight side (s).
Point being, they missed the mud estimate by a yard. Damned near wound up
cold jointed...would of required tear out.....both were 4" deep "graded"
base. Will need to pour some more weird shaped slabs here.
? is how to calc a perimeter length by 4" deep and get cubic yards for
Hire a different sub?
Perimeter & area are not related
rectangle 2 x 22 & square 12 x 12 both have same perimeter but
greatly different area.
Draw to scale (1/4" to 1') on graph paper , count "large squares" &
"small square" to get an accurate area estimate
Buy a mechanical planimeter, I got a cool antique one on ebay
Draw shape in drafting progam that does area calcs
All good alternatives.
In addition, for a field at least "sanity check", outline the area
similarly to the graph paper technique--lay out some
squares/rectangles/triangles/circles that are easy to compute and that
encompass the actual area. You will at least not be short and by
judicious selection of areas, be pretty precise.
A yard at 4" depth would be roughly 80 sq-ft of surface area to give an
idea of the precision needed and the amount their estimate was off by.
One other thing to remember: An error in the smallest dimension
produces the greatest shortage/overage. Make sure the depth is
accurate. This can be easily missed when casting slabs on grade. Is
it really 4"? If it's 5" you're going to off by 25%. On a 10 yard
pour, that's pretty significant.
I'd rather be throwing an extra yard away than finding myself a yard
Thanks all for answers/suggestions. I looked to high heaven for a calc. I
could use the perimeter distance with to no avail.
Rico, I did run it thru SK5 but was trying for a perimeter solution. I've
always 'boxed' the pour in segments as suggested but was hoping there was a
way to do it thru a perimeter measurement.
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