Building on Lake Austin: shoreline setbacks and the 1982 dividing line
The shoreline setback, and the 1982 dividing line
Everything here is measured from the shoreline, which §25-2-551(A) defines precisely as the 492.8 topographic contour line — not the water's edge on the day you visit.
The setback from it is 75 feet. It drops to 25 feet only where both of these hold:
- the lot is in a subdivision plat recorded before 22 April 1982, or is a legal tract exempt from the requirement to plat; and
- the distance between the shoreline and the front lot line (or the tract's property line) is 200 feet or less.
Both limbs. An old lot that runs 300 feet back from the water does not get the reduction — the relief is aimed at shallow lakefront lots that would otherwise be unbuildable.
What may stand in the setback area
§25-2-551(B)(3) starts from a prohibition — no structures in the shoreline setback area — then lists what is permitted anyway:
- a bulkhead, retaining wall or fence;
- a dock, public boat ramp or marina;
- a non-mechanized pedestrian access facility; and
- an on-site sewage facility, under Chapter 15-5.
Each must still comply with its own regulations elsewhere in the title — the exception permits the category, not the specifics. Note "non-mechanized": a funicular or lift down to the water is not within this list.
| Slope gradient | Platted <strong>before</strong> 22 Apr 1982 | Platted <strong>after</strong> 22 Apr 1982 |
|---|---|---|
| 15% or less | 35% | 20% (applies up to 25%) |
| More than 15%, up to 25% | 10% | 20% |
| More than 25%, up to 35% | 5% | 10% |
| With a transfer under (D) | 40% | 30% |
Impervious cover under §25-2-551(C). The two schedules are structured differently — the older one has four slope bands, the newer one three — so they are shown side by side rather than merged. On steep ground an older lot is treated more harshly, not less.
Older lots are not simply better off
It is tempting to read the 1982 date as "old lots get more". On the shoreline setback that is true — 25 feet instead of 75. On impervious cover it is only true on flat ground.
- Gentle slopes — a pre-1982 lot gets 35% against 20%. Substantially better.
- Between 15% and 25% gradient — the pre-1982 lot drops to 10% while the post-1982 lot stays at 20%. The older lot is now worse off.
- Between 25% and 35% — 5% against 10%. Worse again.
Five percent impervious cover on an acre is about 2,178 sq ft for the house, the driveway and everything else together. On steep lakefront that is the number that decides whether a site is viable.
Transferring impervious cover between tracts
§25-2-551(D) allows impervious cover to be moved, and it is the only route to the higher figures in the table. The conditions are tight:
- only between tracts within an LA district; and
- only from land with a gradient of 35% or less to land with a gradient of 15% or less — steep to gentle, never the reverse.
The land you transfer from must then remain undisturbed if it is in a natural condition, or be restored to one as prescribed by the Environmental Criteria Manual. And the transfer must be documented in a manner approved by the director and recorded in the county deed records — it runs with the land, permanently.
So this is a genuine mechanism, not a paper exercise: you are permanently sterilising one piece of ground to build more densely on another.
Cul-de-sac lots have their own width test
§25-2-551(C)(1) applies to a lot fronting a cul-de-sac in a plat recorded after 22 April 1982, or exempt from platting. It must have:
- a chord width of at least 33 feet at the front lot line;
- a width of at least 60 feet at the front yard setback line; and
- a width of at least 100 feet at all points 100 feet or more behind the front lot line.
That third condition is the one that bites — it means the lot must reach the full LA district width once you are back from the road, so a pie-shaped cul-de-sac lot has to be genuinely large.
What we establish before anything else on a lake lot
The plat recording date, first. Before or after 22 April 1982 changes the shoreline setback by fifty feet and changes the impervious cover schedule entirely. It is a documentary question and it is worth answering before an offer, not after.
Then slope, because the impervious bands are steep-sided. Moving from 15% to 16% gradient on a pre-1982 lot takes you from 35% cover to 10% — a cliff, not a gradient. A topographic survey earns its cost here more than almost anywhere else in Austin.
The setback-area exclusion is the piece of good news worth knowing early. On a shallow lakefront lot the 75-foot setback can be a third of the site, and none of it counts against the impervious allowance.
And we check both shoreline rules. Clients who have researched the 75-foot setback are often unaware that a separate critical water quality zone runs inland from the same contour under a different chapter.
Common questions
Send us an address and we will tell you what we find
We do this research ourselves on every project we take on — zoning, floodplain, watershed, trees, whether it is a legal lot. Send us an address and we will run it and tell you what we find. It works the same whether you own a vacant lot, a house you are thinking of adding a unit to, or a house you are thinking of replacing. No charge and no strings, and if it is a bad lot we will say so.
Send us an addressWe are homebuilders, not the City of Austin. This page explains how we read the code in practice — it is not legal advice and it is not an official determination. Always confirm with Austin Development Services before you rely on it for a project. The authoritative text is the Austin Land Development Code; permitting questions go to Austin Development Services Department.