More Floor Area, Lower Land Basis

Say a broker sends you a 200 × 200 ft lot in Dallas. Forty thousand square feet of dirt, $1 million, and a one-line pitch: it'll take 150 apartments. Before anyone draws a unit, one cell in the zoning record answers that, and it is a different cell depending on which district the lot sits in.

The record here is the Dallas profile in this repo, Chapter 51A of the development code, verified April 19, 2026. It holds 45 base districts. I'm going to put the same lot and the same check in three of them and watch the answer move.

Same lot, three answers

MF-4(A), the apartment district. This is the highest multifamily row: 240 feet, 80 percent coverage, and an empty floor-area cell. Dallas doesn't count apartments by floor area or by units per acre. It counts them by lot area per unit: 225 square feet of lot per efficiency, 275 per one-bedroom, 325 per two-bedroom. So 150 one-bedrooms need 150 × 275 = 41,250 square feet of lot. The lot has 40,000. The answer is 145 one-bedrooms (40,000 ÷ 275), or 123 two-bedrooms, or 177 if every unit is an efficiency. Getting to 150 means the mix has to carry efficiencies: at least 25 of them, since 25 × 225 + 125 × 275 is exactly 40,000. At 145 doors, the land is about $6,900 a door.

GO(A), General Office. 270 feet, a height note of 20 stories, 80 percent coverage, a floor-area ratio of 4, and setbacks of 15 feet front and 20 side and rear. The use line in the record reads office, lodging and limited retail. Read alone, the row gives you 4 × 40,000 = 160,000 square feet of office and no apartments. But Texas SB 840 has applied in Dallas since September 1, 2025 (city 1,304,000 people, county 2,613,539, against thresholds of 150,000 and 300,000), and on office, commercial, retail, warehouse and mixed-use land it makes multifamily a by-right use. The record shows that by going blank: density and parking on this row are marked preempted by the state. Height, coverage and the floor-area ratio stayed filled.

CA-1(A), Central Area 1. Downtown. Height stored as unlimited, coverage 100 percent, setbacks zero, a floor-area ratio of 20, and no density cell at all. The record's own description is "effectively unzoned for density." At FAR 20 the lot carries 800,000 square feet. Nothing on the row stops 150 apartments. If a downtown lot this size is really listed at $1 million, the zoning is not the thing I'd check first.

What the comparison below shows

The applet fixes the lot at 200 × 200 ft, the land at $1 million, and the proposal at 20 floors of 12 feet. The only thing that changes is the district. Card A stays pinned to GO(A) and draws dashed. Card B opens on CA-1(A); press Play and it steps through the other 44 Dallas districts, smallest modeled building to largest. Each card reports the modeled floor area and the land cost per floor square foot, and names the limit that stopped the building.

The opening frame: GO(A) models 160,000 square feet, or $6.25 of land per floor square foot. CA-1(A) models 800,000 square feet, or $1.25. That's 640,000 square feet more and $5.00 less per foot. Rent, construction cost and time still decide the return. This is the land basis, nothing else.

The distinction worth keeping is between the ceiling and the building. GO(A)'s setbacks leave a 160 × 165 ft footprint, 26,400 square feet. Twenty floors of that would be 528,000 square feet. FAR 4 stops it at 160,000, a little over six floors. The 270-foot height cap never comes into play. "20 stories" on that row is a height limit, not a building you can buy. On CA-1(A), twenty full-lot floors land at exactly FAR 20, which is the only reason the five-to-one ratio between the two cards survives the drawing.

Now watch the end of the tour. The biggest boxes are not the loosest districts. MF-4(A) draws 630,000 square feet because its FAR cell is empty and the model treats a missing limit as no limit; the card labels it provisional and refuses to price the land. Parking, P(A), and Townhouse 1 through 3 draw the full 800,000, because nearly every cell on those rows is either missing or preempted by SB 15. That's bookkeeping, not permission. And the MF-4(A) tower is the cleanest example of what the model can't see: 630,000 square feet over 145 one-bedrooms is about 4,345 square feet per one-bedroom. Nobody builds that. The lot-area rule binds long before the envelope does, and the applet counts floor area, not doors.

The limit of the record

This is a base-district chart, and an aging one. The source was last retrieved April 7, 2026; the April 19 upgrade couldn't re-fetch it, because the code host returns a 403 to scripted requests. The record itself says more than 800 planned developments dominate real entitlement on medium and large Dallas projects, and a PD's own regulations can replace the chart; the record's example is PD-784 along the Trinity River corridor. It lists 20+ historic and conservation districts, a 45-degree proximity slope next to residential, an extra 10 feet of front setback above 45 feet, and tower spacing above the podium. None of that is in the rectangle. Neither is SB 840: the applet runs the base schedule and says so.

SB 840 is where the GO(A) answer gets interesting, and where the record runs out. The repo's Texas pathway summary of the enacted bill says a qualifying project's density limit can't be lower than the greater of 36 units an acre or the highest residential density allowed in the city, and that municipal floor-area limits are prohibited. Thirty-six an acre on 0.92 acres is 33 units. "The highest residential density allowed in the city" is the phrase that decides whether the office lot clears 150, and nothing in this record says which Dallas number that is. If it reads to MF-4(A)'s per-unit rates, the office lot carries at least what the apartment lot does, and its FAR of 4 drops away. CA-1(A), with no density cell at all, makes even that reading arguable. That's a reading, not a ruling. The bill also excludes sites within 3,000 feet of an airport or military base, and the record flags Love Field and Dallas Executive Airport.

So, 150 apartments? On MF-4(A): no, not as all one-bedrooms; 145, or a mix that leans on efficiencies. On CA-1(A): nothing in the row stops it. On GO(A): the base schedule says no apartments and 160,000 square feet; the state says apartments by right with no FAR cap; the record can't settle the count. My judgment: underwrite the doors from the density rule, the floor area from the smallest of the four limits, and treat every blank cell as a question for the Dallas Development Code, not an answer. Read the height. Then read the blank.