Same Lot, Different Date
How many homes can you build on a standard SF-3 lot in central Austin? Two. Three. Three, and maybe on three separate lots. Every one of those answers has been right on some day since late 2023. Nothing about the dirt changed. The calendar did.
So hold the lot still. The Austin profile in this corpus gives SF-3 a 5,750 sq ft minimum lot and a 50 ft minimum width, which makes the minimum lot 50 ft wide and 115 ft deep. Setbacks are 25 ft front, 5 ft side and 10 ft rear. That leaves an 80 × 40 ft buildable box, 3,200 sq ft. Coverage stops at 40%, or 2,300 sq ft, and height at 35 ft. The record calls SF-3 the default zoning of most of central Austin, which is why I picked it. This is the lot people actually ask about.
Five dates, one lot
Before December 7, 2023. A duplex by right. That is the record’s implication, not its data: the profile stores today’s rules and credits HOME with the third unit, so two is what was there before. It doesn’t store the old use table, and I’m not going to fill it in from memory.
December 7, 2023: HOME Phase 1 (Ord. 20231207-001). Up to three homes by right on SF-1, SF-2 and SF-3 lots. Same lot, same setbacks, one more home. The profile notes floor area up to 0.65 for the three-unit use: 0.65 × 5,750 = about 3,740 sq ft on this lot. It also marks SF-3 floor area as only partly sourced, so treat that number as a lead, not a limit.
May 16, 2024: HOME Phase 2 (Ord. 20240516-006). The minimum lot for a small-lot home falls from 5,750 to 1,800 sq ft. Divide: 5,750 ÷ 1,800 = 3.19. By area alone, this lot now holds three lots of about 1,917 sq ft each. The Austin research file adds a 2,300 sq ft cap on a small-lot home and a waiver of Subchapter F compatibility on those lots. Area is the easy part. Frontage, access, utilities and the subdivision process decide whether the three lots exist, and none of that is in this record.
July 10, 2025: Austin’s 2024 building code takes effect. The city adopted it in May 2024. It applied fourteen months later. The 2024 is the model code’s publication year; July 10, 2025 is the day Austin started using it. Those are different facts. The zoning answer doesn’t move on this date, but the allowance is only the first budget. Exits, fire separation, accessibility, structure and energy all consume space or money, and this is the date the book that prices them changed. (A house goes to the residential code. This record doesn’t hold Austin’s residential edition.)
September 1, 2025: Texas SB 840. The big state law. On this lot it does nothing. The state record says SB 840 doesn’t apply to SF-zoned land. An Austin commercial lot gains multifamily by right the same day; the SF-3 lot reads exactly as it did on August 31.
What the control shows
The control below holds the lot fixed and steps the as-of date through those five records. The marker on the timeline is the day you’re standing on. Blue ticks changed what the lot allows; gray ticks passed without touching it. The cards read the record for that day: homes by right, the smallest lot a home can sit on, how many lots the area divides into, and Austin’s building-code edition. The lot, its 35 ft height, its 40% coverage and its base setbacks stay fixed, because none of the five dates changed them in this record. Watch the last two frames. Two of the five dates, including the big state law, leave the lot’s answer exactly where it was. How big a law is and what it does to your lot are separate questions.
Where the record runs out
The Austin profile is a snapshot. It was retrieved April 26, 2026, against a code supplement effective November 3, 2025, and it stores today’s values with HOME layered on as notes. The time machine reconstructs the earlier states from those notes. It is not reading the old ordinances. A missing key stays missing.
Three more holes, all visible in the files. First, the two HOME dates are labeled amendment_effective, and they are the same dates written into the ordinance numbers. Austin’s own building code shows how far adoption and effect can drift, fourteen months, so I’d read each ordinance’s effective-date clause before pricing a closing against it. Second, the records disagree with each other: the Austin profile dates SB 15, the small-lot law, to September 1, 2025, while the Texas state record leaves the date blank because its source gave only a year. Third, the profile still stores one parking space for SF-3, even though its own notes say Austin eliminated parking minimums effective November 12, 2023. Read the number without the note and you’d draw a driveway the city stopped requiring.
The biggest gap: nothing in this corpus says which date your project gets. The day you bought the land, the day you filed, the day the permit issued? That is the vesting question, meaning which date locks in the rules for a given application, and there is no vesting record here. Ask the city, then your lawyer, before you trust any of the five.
My judgment: a zoning number without a date is a rumor about the present. On this one lot the calendar moved the answer from two homes to three, then to three possible lots, and the biggest state law of the bunch moved nothing. Put the as-of date next to every number before you price land, and put the application date next to that.