Single-rate approximate estimating

Single-rate approximate estimating

there are commonly three methods are used for single rate approximate estimating.

1)  Unit of accommodation method

as we know that Single-rate approximate estimating method
is commonly used by national bodies such as the education and
health services at the inception stage of construction. If a client has an amount of
money to spend (a budget) then it would be possible to consider the likely number
of functional units which can be provided. From experience, it might be found
that the cost of providing a study bedroom in student accommodation is £20 000.
Using this figure an expenditure of £12 million would provide accommodation
for approximately 600 students. On the other hand if the number of units is
known, a budget cost (usually expressed as a cost range) can be calculated.
Providing there are recent comparable data available, the unit method is useful
where a simple and quick cost range is needed in the early stages. It is difficult,
however, to adjust the costs for specific projects, in different locations, with varying
ground conditions and so on.

2)  Floor area method

In floor area method:-
The main reason for the popularity of the floor area method is its simplicity.There
are few rules to remember and the cost per square metre is well understood by
property developers. A proposed building is measured at each floor level (between
inside faces of external walls); no deductions are made for internal walls, stairs or
lift zones. Previous similar building costs are used by dividing the construction
cost by the internal floor area. Adjustments can be made for location and inflation;
but specification adjustments are much more difficult to estimate. Subjective judgements
are made for size, shape, number of storeys, services, ground conditions and
standard of finishes. A separate assessment should be made for external works, demolitions,
incoming services and drainage which can be significantly different for
similar buildings.
There are many buildings where the unit of accommodation method is impracticable;
such as warehouse projects or open-plan offices. In these cases the superficial
floor area method is found to be reliable with an accuracy of 10% to 15%. This
method also works well with certain external works contracts such as concrete
paving or macadam surfacing.
Sometimes contractors are asked to quote for building work using sketch drawings
and a square metre price. It is unlikely that a contractor would risk signing
a contract on this basis. First a clear scope of works would be needed together
with a site survey and soil investigation report.The price must accurately reflect
the amount and specification of works.

3) Building volume method

In building volume method There are several methods, which use the volume of a building as the cost yardstick,
but they are not widely used today. In some European countries, architects and
engineers are familiar with building costs expressed as cubic metre prices. In
Germany, there are publications, which list typical building costs in terms of their
volume, and the procedure for calculating volumes is given in a DIN standard.







these are the methods for single rate approximate estimating.









regards
pra@rocks