Austin downtown zoning: CBD and DMU height, floor-to-area ratio and setbacks

Two districts, and the second is not a smaller version of the first

Downtown Austin carries two base zoning districts. They are not a ladder — the gap between them is large, and it is widest in the figure that decides how much building a site yields:

• CBD (central business district) — 350 feet, 8:1 floor-to-area ratio
• DMU (downtown mixed use) — 120 feet, 5:1 floor-to-area ratio

Both allow 100 percent building coverage and 100 percent impervious cover. On a 10,000 square foot lot, CBD permits 80,000 square feet of floor area and DMU 50,000 — the same land, 30,000 square feet apart.

For scale, the most permissive district outside downtown is CS at 2:1. CBD is four times that.

Compatibility standards do not apply in CBD

Everywhere else in Austin, the thing that actually limits a commercial building next to housing is not the base district — it is compatibility standards. In the central business district they are switched off. §25-2-581(B) is unusually blunt about it:

Notwithstanding any other provision of this chapter, the requirements of Article 10 (Compatibility Standards) do not apply.

That single sentence is why 350 feet at 8:1 is a real number in CBD rather than a theoretical one. In GR or CS the table figure is routinely unreachable because a nearby house pulls the height down. In CBD nothing does.

DMU is not named in that provision. §25-2-581 applies, by its own terms in subsection (A), in a central business district. Do not carry the exemption across to a DMU site.

Rainey Street: CBD zoning, and a 40-foot residential cap

This is the fact most likely to cost someone money. A Rainey Street site can be zoned CBD and still not get anywhere near 350 feet, because §25-2-739 — which lives in the waterfront overlay article, not the commercial district article — overrides it.

For property in the Rainey Street subdistrict zoned CBD after 17 April 2005:

• For a residential or mixed-use building the maximum height is 40 feet, except as provided below.
• An applicant may exceed 40 feet and reach 8:1 if at least five percent of the dwelling-unit square footage developed within that 8:1 is available to households at or below 80 percent of median family income for the Austin metropolitan area.
• Mixed-use projects must provide that on-site affordable housing in proportion to the share of project floor area devoted to residential use.
• The affordability period is 40 years for rental and 99 years for on-site for-sale housing, running from the date a certificate of occupancy issues. For-sale units are subject to a resale-restricted, shared equity agreement approved by the director of Neighborhood Housing and Community Development.
• An applicant may not deny a prospective tenant affordable rental housing based solely on participation in the Housing Choice Voucher Program or any other rental assistance voucher program.
• The bedroom count mix of the affordable units must be proportional to the development's overall bedroom mix — so the affordable share cannot be pushed into the smallest units.
• A unit counts as affordable only if the household spends no more than 30 percent of gross monthly income on the mortgage or rent.
• On Red River Street from Cesar Chavez to Driskill, and on River Street from I-35 to its western terminus, sidewalks must be at least ten feet wide.
• A use with a drive-in service is prohibited.

So on those lots the affordability condition is not a bonus layered on top of the base entitlement. It is the mechanism by which the base entitlement becomes available at all.

And 8:1 is not the top even here. §25-2-739(C)(5) lets Rainey Street development go further through the Downtown Density Bonus Program — but only on the part that goes further. To achieve bonus area above 8:1 or height above 40 feet, development must comply with §25-2-586, and those requirements "apply only to that portion of development that exceeds a floor-to-area ratio of 8:1 or height above 40 feet".

Read (C)(4) and (C)(5) together and Rainey Street has two stacked gates rather than one: the five percent affordability condition to reach 8:1 and leave 40 feet behind, then the bonus program for anything beyond that.

But the two sections disagree about where the second gate starts. §25-2-739(C)(5)(a) says the bonus program governs above 8:1 or height above 40 feet. §25-2-586(B)(2) — inside the bonus program itself — says Rainey Street may use that program only for floor-to-area ratio above 8:1 or height above 350 feet, and that any height between 41 and 350 feet runs through §25-2-739(C)(4) instead.

They cannot both be right on height. The more specific provision — and the only one that names an upper figure — is §25-2-586(B)(2), which would mean the affordability route carries a project from 40 feet all the way to 350, with the bonus program taking over above that. We state the conflict rather than pick a side. On a real Rainey Street project this is a question to put to the city in writing.

Two smaller provisions worth knowing

Commercial parking as a use. In both CBD and DMU, commercial off-street parking is a permitted use when it is less than 50 percent of the spaces in a parking structure. Cross that threshold and the structure is a commercial parking facility rather than accessory parking, which is a different use question entirely.

Convention center sites. A convention center use in CBD needs Council approval of its site plan, and that approval does something unusual — it establishes the site development regulations and waives any that conflict with the approved plan. A public hearing is required for each such site plan. In effect the site plan becomes the zoning.