In the procedure for the estimation of brickwork, two
approaches - Centre-line, and Long- and Short-wall methods - are applicable.
While in the case of centre-line approach (in straight forward cases), the
total length dimension remains unchanged with the width and height of the
masonry courses (in footings, plinth, and superstructure) varying according to
the design as detailed in the given section of the wall; but the length
dimensions (as well as width and height) in long- and short-wall method do
register a change from course to course (Figure
1).
In fact there are no strict straight-jacket rules for arriving at
(taking out) dimensions from the plan, elevation, and sectional drawings -
experience and suitability (vis-a-vis, each drawing) always guide one dividing
a plan into parts so that the dimensions are easily worked out for ultimately
computing the quantities
Three procedures (for the sake
of clear understanding of full basics of the mode of mensuration) however, are
available concerning the quantification of foundation work - excavation, concreting
and masonry - and superstructure in a given building as listed below:
(a) out-to-out
and in-to-in method (i.e., long- and short-wall method),
(b) crossing
method, and
(c) centre-line
method.
Out-to-out and in-to-in method is the most commonly adopted procedure.
Here the length of long walls (say for excavation purposes) are
reckoned from out to out - AB in Figure 1 - and, the length of short walls
measured in between the long walls in-to-in - EF. These lengths shall,
obviously, apply to foundation concreting also. The magnitude of these dimensions
changes (in fact, decreases) for long walls, and increases for short walls at
every change in the breadth (or, ray, thickness) of a course of brickwork:
AB Will
decrease to (AB-2X(b1-b2)/2),i.e.for the first footing of the
foundation masonry the length of long wall shall be (2 - 3). And EF shall
increase by same amount, becoming
(EF+2x(b1-b2)/2),i.e(5-3).Here
,the width for excavation is bland height (or thickness,
vertically) is dl; while for the first footing, width = b2, and depth =
d2. Similarly, in the plinth course (or for next footing if it is there), long
wall length shall be [(10) - (11)], and short-wall length shall be [(15) -
(16)] - width being b3, and depth = (d3+ d4). And for the superstructure,
long-wall will have a length [(18) - (19)], and short wall length will be [(23)
- (24)] - width being = b4, and height = height of the room from the top of DPC
(of floor top) to the underside of roof slab (or whatever it is). Here it is
important to point out that the width and depth of excavation shall be bland
(dl+ d2+ d3), respectively; while for foundation concrete the values
will be bl and dl, respectively.
Fig-1:A simple Rectangular Trench
Plan of a Building and section of wall-Cum-Foundation
It is obvious that with the decrease in the thickness of walls of a
room, (i.e. proceeding up from the first footing towards the superstructure)
the length of a long wall decreases, whereas the length of a short wall
increases in accordance with the breadth (or, thickness as it is generally
designated). At the plinth level, the length of long wall = the length of the
room (wall to wall, i.e. inner dimension plus twice the wall thickness; and the
length of short wall = width of the room (inner dimension). If the thickness of
the walls is different, the dimensions are reckoned accordingly.