Floor Area Ratios simplify defined is the area of a building divided by the area of its lot (Land area). The formula is Floor area Ratio = Building Area / land area. The floor area ratio is often limited by local zoning codes. Make sure you contact your local planning department to verify local zoning codes and rules that may apply to your final floor area ratio calculation. Also, remember that a correct floor area ratio can have a impact on the final land value that is assessed by the local property tax assessor.
The floor area ratio is a relatively simple concept that is only complicated by a number of factors and traps for the unwary. Example: Is the lot flat? Is it sloped? Can anything else besides the floor area be factored into calculation of the building square footage?
Here is a list of complicating factors to be aware of with regard to the land portion of the calculation:
Here are some factors to be aware of with regard to the building portion of the calculation:
Excessively High Ceilings
Other unaccounted for common areas
How to move forward when you have a complicated Floor Area Ratio?
First, you should contact your local building department to review their use of their floor area ratio calculations if you are not sure. Often they will be able to tell you exactly how they determine a complicated floor area ratio for use within their jurisdiction. Let them provide the ratio and verify on your own. Also, if you are still not sure if your calculation is correct, contact a local real estate professional and let them guide you through the process.
Remember, unexpected delays in calculating, verifying and working with the local planning departments can cost you time, which is your money! Work smarter, not harder.