Construction floor area is used to measure and estimate costs related to the construction of a building. A building's construction floor area is important for not only controlling costs, but also for designing standard fixtures and other physical properties found in most residential and commercial structures. Knowing the size and layout of construction projects ahead of time can also help builders gauge energy consumption needs and improve energy-efficiency in the building.
Washington State University's publication "Building Area Measurement" states that construction floor or building area can be broken down into different categories. Gross square footage, which is the total construction floor area, sums all areas for all building floors. This includes the surface area and thickness of exterior walls, excavated basement areas, and inner and outer balconies. Gross square footage comprises net usable square footage and structural square footage. Usable square feet specifically refers to floors used by occupants or equipment. Structural square feet measures the total floor area dedicated to non-occupant use. Examples of structural floor area are exterior walls, fire walls, permanent partitions and areas in attics and basements.
Local zoning laws vary across municipalities and may exclude certain building elements in calculations for construction floor area. For example, the town of Stonington Connecticut excludes areas including elevator and stair bulkheads, accessory water tanks and cooling towers, terraces, outdoor steps and unroofed open porches from construction floor plans. On the other hand, basement and attic floors (whether they have been laid or not); interior balconies and mezzanines; and garage roofs are included in total gross feet measurements for construction floor area.
Builders divide construction projects into different structural components or elements, which can be filtered into a cost analysis. For example, the construction floor area may be broken down into structure, foundations and curtain walling. These elements are further divided into sub-elements such as basements, ground floor slabs, frames and roofs. Moreover, measurement rules categorize elements for calculating construction floor area and estimating costs. Consultant fees, furniture, equipment and other nonstructural costs are also included in the cost model for construction projects.
Tools such as floor plans are highly useful for figuring out construction floor area. Measuring "off plan" entails using both floor plans drawn to scale and architectural drawings. Additionally, the Building Owners and Managers Association (BOMA) International provides three different measurement standards and methodologies for calculating the size of commercial spaces such as shopping centers. These include construction gross area, exterior gross area and gross leasable area (see Resources).