The
shape of a building has an important
effect on cost. As a general rule
the simpler the shape of a building,
the lower will be its unit cost. Let
us illustrate this as follows:
This determines the cost per square
meter of building
A.
IRREGULAR SHAPES
Example of how
building cost per square meter can
vary 
Cost per
square meter
BUILDING A
Example of how
building cost
per square meter
can vary
BUILDING B
We
note that both plans have exactly
the same floor areas, yet building B
is far more expensive due to the
shape of its design. Reasons for the
increase in costs are:

Building B has a higher
perimeter/floor area ratio (to
be discussed in more detail
later) and requires 6% more
external walling to enclose the
same floor area than A.

Setting out costs will be
increased by as much as 50%.

Excavations will cost between 6%
and 20% more.

Drainage costs will increase by
approximately 25% due to the
extra manholes and extra length
of piping needed.

Additional costs will also
result from other elements of
the building such as the walling
and roofing due to the work
being complicated by the shape.
It
can therefore be concluded that the
irregular shapes of buildings add to
their overall cost.
B.
REGULAR SHAPES
Regular shapes in contrast, become
more expensive the longer and
narrower they are planned. This can
be illustrated by the following
examples of a square and rectangular
building with the same floor area.
BUILDING A
BUILDING B
Example of how
building
Cost per
square meter can vary
CASE
A
Area
on plan = 400m²
Length of walling = 80m
Assume 3m high walling @ Currency
200.00/m²
Then
cost/m² = 80 x 3 x 200 ÷ 400
= Currency
120.00/m²  cost per
square meter
CASE
B
Area
on plan = 400m²
Length of walling = 208m
Assume 3m high walling @ Currency
200.00/m²
Then
cost/m² = 208 x 3 x 200 ÷ 400
= Currency
312.00/m²  cost per
square meter
The
length of building B thus resulted
in an additional expense of Currency
76,800.00 over that of Building A
influencing
cost per
square meter 