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Construction Industry/Principle in construction economics


What is approximate quantity and advantages and disadvantages

Hello Teetee,

Approximate quantity is the process of estimating a construction project.  This can be done at various stages of the project prior to ground breaking.  Listed are several methods of estimating:
    1. Service Unit.  The cost of a nursing home project may be determined by the number of beds in the facility. A hotel cost may be estimated by the number of guest rooms.
    2. Floor Square Footage:  Use a dollar factor for each square foot of floor area from the footprint plus all floors above.  Frequently a basement or attic are not calculated in this method.
    3. Cubic Footage.  This method is more accurate that the previous calculation.  The area accounts for height as well as plane area.
    4. Detailed Quantities.  A shopping center or warehouse project that has repetitive areas of similar size; i.e. the cost of each "bay".
    5. Comparative Costs.  This method applies to similar projects; residences, office buildings, schools, etc. where previous (but recent) costs can be used to determine the budget of a new project.

An Architect's estimate:  This is usually a conservative estimate and is often used to determine an initial project budget.  It is based on the area of the building - square footage of the footprint with consideration as to multiple stories.  The Architect relies on past experience of similar projects.  For example; a recently built residence of 2000 s.f. had a final cost of $200,000 or $100 per square foot. This factor is an approximate estimate.
The only accurate way to determine costs is with the use of completed plans and detailed specifications. When the drawings and specifications are finished, the Owner or Architect will invite a minimum of three contractors to submit bids on a specific date and time and on a submission form prepared by the Architect.

The accuracy of the estimate is a factor of the details of the plans and specs. For example, various products used in the construction may be detailed and specifically itemized in the specs such as specifying a particular model of a product.

Since there are four or five methods of estimating, each process has an advantage, one over another, based on the detail of planning and preparation of construction plans.  Conversely, the disadvantage of an estimating method may depend on the person preparing the estimate.

I hope this has been helpful.


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Roger Zona


I am experienced in all types of construction: residential, industrial and commercial; single family, multi-family, mid-rise and high rise buildings (16 story office building) as well as remodeling, additions and tenant improvements. I can field most any question that relates to general construction. I have consulted with infrastructure (utility) contractors also and have a good general knowledge of underground utility construction for subdivisions and commercial projects.


After college, I began my career in the construction industry. I chose to become an apprentice Architect and 4 yrs later I opened my own architectural design firm. Six years later I moved to Florida to buy & develop land and build. I became a State of Florida Certified General Contractor and operated my business for 45 years. I built all types of residential and commercial buildings including warehouses, shopping centers, high rise apartments and office buildings and developed sites for other contractors. I retired and became a consultant to the construction industry. I maintain my license and continuing education requirements, operate a small construction company and write a weekly newspaper column for the Palm Beach Post (a Cox publication) with the byline "Ask The Contractor". I am the "technical editor" for a publisher of books that relate to home maintenance.

Previously - NAHA Currently - FLCA (Florida Licensed Contractors Assoc.)

Palm Beach Post newspaper - weekly Q & A column Happy Herald monthly real estate publication - monthly column

Michigan State University University of Detroit BS in Engineering

Past/Present Clients
I built a home in Palm Beach for a member of the Pulitzer Family. I was responsible for the completion of a twin hi-rise condominium project for G.E. Credit. I was a partner in the successful development of a P.U.D. (Planned Urban Development) subdivision. I represented the largest home builder from France (Bati Service, S.A.) in the development of a subdivision and the design and construction of the homes.

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