Barton Springs Zone and Save Our Springs: what applies to a house

Last verified August 5, 2026 against the Austin Land Development Code · KiliGray Homes

The Save Our Springs ordinance limits impervious cover to 15% in the Edwards Aquifer recharge zone, 20% in the Barton Creek contributing zone and 25% elsewhere in the contributing zone — but it does not apply to single-family or duplex work on a lot that existed on 1 November 1991.

Applies to: Development in the Barton Springs Zone — the Barton Creek watershed and all watersheds contributing recharge to Barton Springs. Both Article 12 and Article 13 apply.

Two sets of rules, applied together

Development in the Barton Springs Zone answers to two separate articles of Chapter 25-8, and §25-8-481(B) is explicit that you must comply with both:

Article 12 — Barton Springs Zone Requirements. Water quality transition zone restrictions and a prohibition on transferring development intensity.
Article 13 — Save Our Springs Initiative. The impervious cover caps and pollutant loading requirements, adopted by popular vote on 8 August 1992.

This matters because the well-known exemption for older residential lots is written into Article 13 only. It does not switch off Article 12.

If you are worried about the 15% limit on an existing house lot, read this first. §25-8-516(A)(1) provides that Article 13 does not apply to development on a single platted lot, or a single tract not required to be platted, that existed on 1 November 1991, where the work is construction, renovation, additions to, repair or development of a single-family, single-family attached or duplex structure used exclusively for residential purposes — plus improvements incidental to that use. For most existing homes in the zone, the SOS impervious cover caps are not the operative constraint.

What SOS requires when it does apply

§25-8-514(A) sets impervious cover limits by where you sit relative to the Edwards Aquifer, calculated on a net site area basis:

15% in the entire recharge zone;
20% of the contributing zone within the Barton Creek watershed;
25% in the remainder of the contributing zone.

Set against the 45% an SF-3 lot normally gets, 15% is a different kind of project altogether.

And the percentage is a ceiling, not a target. The same subsection requires runoff to be managed so that no increases occur in average annual loadings of total suspended solids, phosphorus, nitrogen, chemical oxygen demand, lead, cadmium, E. coli, volatile organic compounds, pesticides and herbicides. It then says plainly that "impervious cover shall be reduced if needed to assure compliance with these pollutant load restrictions." You can be under 15% and still be required to go lower.

No waivers, and a supermajority to change it

SOS is unusually hard to get around, by design. §25-8-515 provides that its requirements are not subject to the exemptions, special exceptions, waivers or variances allowed elsewhere in Chapter 25-8. The only route to relief is a limited adjustment under §25-8-518, which exists to resolve possible conflicts with other laws — not to accommodate a design.

It is also hard to amend. §25-8-512: the article may be repealed or amended only by an affirmative vote of a three-quarters majority of council. That follows from its origin — it was adopted by popular vote, not by ordinary council action.

The same restriction reaches the Barton Springs Zone generally: §25-8-483 prohibits transferring development intensity anywhere in the zone except as part of a §25-8-518 adjustment. The transfer mechanism that softens impervious cover limits in other watersheds is simply unavailable here.

Wider creek buffers, and a flat building ban

§25-8-514(B) amends the ordinary critical water quality zone rules inside the contributing watersheds. Two effects:

the zone boundary may in no event be less than 200 feet from the centreline of a major waterway, or less than 400 feet from the centreline of the main channel of Barton Creek; and
no pollution control structure, and no residential or commercial building, may be constructed in the critical water quality zone in those watersheds.

The second is worth reading twice. Elsewhere the zone permits a limited set of structures. Here, buildings are simply out.

The water quality transition zone: two acres, one unit per three

Article 12 governs the band outside the critical water quality zone, and it splits on whether you are over the recharge zone.

Over the Edwards Aquifer recharge zone — development is prohibited, except for what Article 7 Division 1 already allows in a critical water quality zone, plus minor drainage facilities and water quality controls meeting §25-8-263. There is no residential exception.

Outside the recharge zone — prohibited too, but with a residential route: duplex or single-family housing with a minimum lot size of two acres and a density of not more than one unit for each three acres, excluding acreage in the 100-year floodplain. Streets are also permitted.

Note how that pairs: a two-acre minimum lot, but a density of one unit per three acres. The lot minimum and the density cap are different numbers doing different jobs, and the density figure is calculated after floodplain acreage is taken out.

The 8,000 square foot alternative

Alongside the residential exemption, §25-8-516(A)(2) exempts development of a maximum of 8,000 sq ft of impervious cover on a qualifying pre-1991 lot or tract — including impervious cover existing before and after the development.

That parenthesis is the whole rule. It is a cumulative cap on the finished state of the site, not an allowance for new work. If the site already carries 6,000 sq ft, there is 2,000 left, not 8,000.

What we tell people who own land out there

The first question is always the date. Did the lot exist on 1 November 1991? For a great many established neighbourhoods in the zone the answer is yes, the work is a house, and Article 13 falls away. People arrive expecting to be told 15% and are often relieved.

The second is that Article 12 does not fall away with it, and neither does the ordinary watershed and creek-buffer machinery. "SOS does not apply" is not the same sentence as "no watershed constraints".

On raw land the honest answer is different. Fifteen percent net site area with a pollutant-loading backstop and no variance route is a genuine constraint on what the land can become, and it is better understood before purchase than after.

Common questions

What is the impervious cover limit in the Barton Springs Zone?

Under the SOS ordinance, 15% in the Edwards Aquifer recharge zone, 20% of the contributing zone within the Barton Creek watershed and 25% in the remainder of the contributing zone, on a net site area basis — and lower still if needed to meet the pollutant loading requirements.

Does the SOS ordinance apply to my existing house in Austin?

Usually not. §25-8-516(A)(1) exempts construction, renovation, additions, repair or development of a single-family, single-family attached or duplex structure used exclusively for residential purposes on a single platted lot or tract that existed on 1 November 1991. Article 12 Barton Springs Zone requirements still apply.

Can I get a variance from the Save Our Springs ordinance?

No. §25-8-515 provides that its requirements are not subject to the exemptions, special exceptions, waivers or variances allowed elsewhere in Chapter 25-8. The only route is a limited adjustment under §25-8-518 to resolve conflicts with other laws.

What is the Barton Springs Zone in Austin?

The Barton Creek watershed and all watersheds contributing recharge to Barton Springs, including the parts of the Williamson, Slaughter, Onion, Bear and Little Bear Creek watersheds in the Edwards Aquifer recharge or contributing zones.

Can I build in the water quality transition zone in the Barton Springs Zone?

Over the Edwards Aquifer recharge zone, no residential development is permitted. Outside the recharge zone, duplex or single-family housing is permitted with a minimum lot size of two acres and a density of not more than one unit per three acres, excluding acreage in the 100-year floodplain.

How close to Barton Creek can I build?

Not within 400 feet of the centreline of the main channel — that is the minimum critical water quality zone boundary under §25-8-514(B), and no residential or commercial building may be constructed in that zone in the contributing watersheds.

Working out what you can build?

We build in Central Austin and deal with this code on every project. If you own a lot and want a straight answer about what fits on it, we're happy to take a look.

Talk to us about your lot

We 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.