By Frank Fortino
In a City where the average square foot of property is often worth more than an ounce of gold, it’s safe to say that every inch counts. Developers wrestle with the prospects of building fresh from the ground up, or converting existing structures to fit with modern tastes and aesthetics. For those taking the old to new approach, one simple calculation can make or break the viability of a project – the calculation of Floor Surface Area.
The DOB defines Floor Surface Area as the gross square foot area of all horizontal floor and roof surfaces of a building, at all levels. Making any changes to this – through removing floors, expanding side walls, and raising ceilings can impact the overall Floor Surface Area of the building. Some changes may decrease the Area, while others may increase it. There are implications – since an increase of Floor Surface Area of greater than 110% reclassifies the project as a Alteration Type 1 required to meet New Building Requirements and conform in its entirety to the 2014 Code as if “hereafter erected.”
Calculating the increase in floor surface area is straight forward with the following equation.
((proposed – existing to remain)/existing to remain) x 100 = Percentage increase in floor surface area
With this in mind, the next step is to understand what exactly counts as Floor Surface Area, and for this we can look to Buildings Bulletin 2016-012 for answers. The Bulletin clarifies the following:
- Any floor or other horizontal surface, including roofs, that is entirely removed along with its structure shall not be included in the calculation as existing floor surface area. If a floor, horizontal surface, or roof is entirely removed along with its structure and then replaced, it shall be included in the proposed floor surface area.
- For the purposes of calculating floor surface area, all pitched roofs are to have their areas calculated based on their horizontal footprint – as if viewed from directly above – including any with multiple dormers, gables, or chimneys. However, the floor surface area of any roof is limited to the horizontal footprint bounded by exterior walls of the building. With the exception that roofs covering porches or balconies shall be included in floor surface area even if such spaces are not bounded by exterior walls.
- Floor surface area includes attics. As per BC 202.1, an attic is “the space between the ceiling beams of the top story and the roof rafters.” The floor area of any attic with fixed stairs and/or headroom greater than or equal to five feet is included in floor surface area. If any location within the attic has headroom of greater than or equal to five feet, measured from the bottom of the roof rafters to the top of the floor or the top of the ceiling beams if no floor is laid, the floor area of the entire attic is included in floor surface area.
- Strengthening any structural support, including sistering floor joists or other modifications to the floor or roof assembly, whenever the existing structure is to remain and carry load, will be included in existing floor surface area.
- Any enclosed space with headroom greater than five feet located beneath a building shall be included in the calculation of floor surface area whether or not a floor has been laid.
- Balconies and covered porches shall be included in floor surface area calculations. Uncovered porches and decks at or below the first floor shall not be included in floor surface area calculations
There are clearly considerations here. If the Floor Surface Area expands too much the project may face design and compliance barriers that may not work with the existing structure. The applicant would need to refile all documents and forms and re-identify the project as an “Alteration required to meet New Building requirements.” Importantly, when a change in scope of work occurs that triggers the 110% rule, all construction activity must be suspended. Construction work cannot resume until a post-approval amendment is approved for the expanded scope.
Developers need to consider the 110% rule carefully when evaluating existing structures. They may feel that preserving the integrity of an old building makes no sense if they are subject to the realities of the 2014 Building Code anyway. At the same time, there’s no doubt that our City constantly reinvents itself, by giving new life to old buildings. So long as the 110% increase of Floor Surface Area rule remains in check, that will continue to be a viable option for the right teams.