| Abstract | This work presents a method of pre-design cost estimating model for high-rise office buildings in
Bangkok.
Nowadays, in construction business, feasibility study becomes a preliminary work that needs to
be done in the pre-design stage. Instead of hiring architects and engineers to produce drawings
and specifications, parametric estimating is another way to estimate the project cost without
drawings and specifications. After parametric estimating is done, result may come out with the
budget in which owner can decide whether it should be invested or not. On the other hand, after
a building is constructed, consultant may roughly countercheck contractor by using this method.
Parametric estimating consists of parameters, areas of trade, physical estimating ratios, and unit
prices. The parameter is a function of areas of trade. For example, gross-enclosed floor area is a
function of piling work, curtain wall, fire protection, etc. Office area is a function of floor
finishes, air-conditioning system, passenger lift, etc.
Each area of trade is governed by physical estimating ratio and unit price. Total cost comes from
all costs of each area of trade by multiplying parameter and physical estimating ratio by unit
price_. Unit prices can be updated due to the market condition, the key of parametric estimating,
physical estimating ratios and areas of trade, can also be changed depending on the way to
calculate the ratios since every contractor has its own ratio. As long as parametric estimating has
been using, total cost is still based on these physical estimating ratios.
Physical estimating ratios obtained were tested on the completed project outside the data used.
This shows that areas of trade and physical estimating ratios can be used to estimate buildings
with an accuracy that is satisfactory and reasonable. |