educational estimating tool - not professional advice. every number here is a placeholder until verified. read the full disclaimer.

austin · current code · september 2026

how many homes fit on this lot now

austin's home amendments changed what a single-family lot can hold. type in the lot; this page reads the caps back for one, two and three units and draws them on the same lot.

every default below is an assumption, not a fact about your lot. the lot size, setbacks and the story height are starting figures. the side and rear setbacks are typical numbers, not looked up for a district; the front setback and the unit, coverage, impervious and floor-area caps are checked against the sources cited on each card. a handful are flagged where the primary ordinance text has not been verified word for word. the may 2026 council resolution initiating amendments to the land development code (title 25) to modify site development and other regulations for two- and three-unit residential uses has not changed the code and is not modeled here, nor is sb 15 (local government code ch. 211, subchapter d), which sets other limits on unplatted single-family zoned tracts of five acres or more. built for Austin, Texas - every rule on this page is a City of Austin ordinance. outside Austin, none of the unit counts, caps or citations apply; use this to see what a HOME-style upzoning does to a small lot, then find your own city's equivalent - see the tools page for more on this.

inputs

lot width (ft)street frontage

lot depth (ft)front to rear

lot area (sf)or type it - depth follows

zoning districtsf-1 base is 35% / 40% for a single unit; two and three units are 40% / 45% in all three

existing house to keep (sf)optional - noted, not counted

front setback (ft)two- and three-unit figure

side setback (ft)each side - assumption

rear setback (ft)assumption

inside subchapter fmost central austin sf lots

the same lot, three ways

one unit

the house-and-lot everyone already knows

two units

a main house and a second one, or a duplex

three units

the most home allows on one sf lot

what the lot allows

cap	one unit	two units	three units

code checks - the numbers behind the claims

read this before using any of it

what home changed. before the home amendments the code treated a second unit on these lots as a secondary or accessory use, with guest houses and accessory apartments as categories of their own. phase 1 of the home amendments allows up to three units on sf-1, sf-2 and sf-3 lots of at least 5,750 sf, with building coverage for two or three units capped at 40 percent and impervious cover at 45 percent, and a floor-area cap that steps up with the unit count. phase 2 let a single home be built on a lot as small as 1,800 sf, which lets an ordinary lot be subdivided into smaller lots, each holding one home. every lot in these districts changed what it can hold.

the numbers are the caps, not the design. the floor area on the cards is the most the code lets you build, before the setbacks, trees, drainage, the shape of the lot and the budget have said anything. a real project lands under these figures, sometimes well under. the drawings above are footprint blocks sized to the max footprint on the cards, not floor plans. use the page to know what the lot can hold, then get someone to draw it.

what actually stops a project is usually not zoning. it is a utility threshold you find out about after paying for design, a subdivision process sized for a different kind of project, and a review framework still catching up with the programs the city created. that is its own field note, and the utility side has its own tool: run that one before assuming the three-unit number here is the number.