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contact | Older IBC 2015 Allowable Area Calculator

IBC 2021–2024 Allowable Area Calculator

Jonathan Ochshorn


Directions: First, select a version of the IBC (2021 or 2024) and preferred units (Imperial or S.I.). Enter values for occupancy classification, construction type, sprinklers, and proposed number of stories, as well as building perimeter lengths and distance (widths) from building to property lines. Select "yes" if the building is a high-rise (per Section 403 of the 2021/2024 IBC), or if there are 30 or more occupants at a floor level 55 feet or more above the lowest level of fire department vehicular access (per Section 903.2.11.3 of the 2021/2024 IBC) and so on. Press "update" button.

Values are calculated for allowable areas, heights, and numbers of stories for single-occupancy buildings. The site plan (Fig. 1) corresponds to the default values indicated below for a proposed 4-story, fully-sprinklered office building (occupancy class = B) of type II-B construction. Distances may be measured from the building to the far side of a "right-of-way" [R.O.W.], as is shown for the building perimeter facing east. In this case, the distance is 35 feet. Some occupancies require sprinklers under certain circumstances: see warnings and error messages.

Notes and clarifications:

For more information, see my online building code handout.

site plan with yard dimensions
Fig. 1. Site plan showing yard and building dimensions.