The Corner-Lot Tower That Cannot Be Built
Your client owns a 2,500 m² corner lot zoned C-2 with a 2.5 FAR, a 22 m height limit, 6 m front setbacks on both street frontages, a 3 m side setback, and a 20% minimum open space requirement. The program is 7,800 m² of office over ground-floor retail, plus 60 parking spaces. The planning department applies a 60-degree daylight plane measured from the opposite street line and requires one parking space per 100 m² of gross floor area. The client wants a 12-story tower to "make a statement" and points to a 14-story building two blocks away approved five years ago. Your first massing study yields 6,250 m² of gross floor area at five floors with 4.2 m floor-to-floor. The client says the pro forma needs at least 7,500 m² or the project dies, and asks whether a variance is "a sure thing."
1. Calculate the achievable envelope and explain which regulation actually governs.
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Run the numbers in order and let the binding constraint reveal itself.
FAR: 2,500 m² × 2.5 = 6,250 m² maximum gross floor area. The program's 7,800 m² is 1,550 m² - about 25% - over the envelope.
Height: 22 m ÷ 4.2 m floor-to-floor = 5.2, so five floors at 21.0 m plus parapet and mechanical screening fits; a sixth floor does not.
Daylight plane: measured 60° from the opposite street line. At a 14 m distance from that line, the plane allows 14 × tan 60° ≈ 24 m, already above the 22 m cap; the plane is not governing here, the height limit and FAR are.
Parking: 6,250 ÷ 100 = 62.5, so 63 spaces. At roughly 30 m² per space including aisles, 60–63 surface spaces consume about 1,800–1,900 m², or 75% of the lot. That leaves under 250 m² for building footprint and contradicts the 500 m² open space requirement. Parking, not FAR, is the real binding constraint.
The conclusion: 6,250 m² is the ceiling, the 12-story tower is impossible by a factor of more than two in height, and the site only works if parking moves below grade or off site.
2. The client asks you to design to 7,500 m² and pursue a variance afterward. What do you advise and what alternatives do you put forward?
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Advise against designing to an unentitled envelope. A variance is discretionary, requires findings that include hardship not self-created by the applicant's program, and the 14-story building two blocks away is not precedent - it may predate the current code, have been built with a bonus, or sit in a different zone. Designing to 7,500 m² risks six figures of fees on a scheme the board can simply deny.
Instead, present alternatives that change a variable rather than begging for relief:
- Shared parking. A written agreement with the municipal garage two blocks away could reduce on-site parking to 20 spaces, freeing roughly 1,200 m² and making a 6,250 m² building work on this lot.
- Below-grade parking. One level of underground parking removes the surface lot entirely but adds roughly $35,000–$50,000 per space; test whether the pro forma survives at 6,250 m².
- Density bonus. Many codes trade additional height or FAR for affordable housing or public amenity; check whether C-2 offers a bonus before assuming a variance is the only path.
- Program reduction or a second site. Show the client the yield at 6,250 m² and at 7,500 m² on a larger parcel.
Put the advice in writing with the calculations attached, and ask for a written direction before proceeding.